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Polpharma European CDMO Partner & API Manufacturer since 1951 Polpharma European CDMO Partner & API Manufacturer since 1951


Technical details about Aspirin, learn more about the structure, uses, toxicity, action, side effects and more

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2D Structure
1. Also known as: Acetylsalicylic acid, 50-78-2, 2-acetoxybenzoic acid, 2-(acetyloxy)benzoic acid, O-acetylsalicylic acid, Acetylsalicylate
Molecular Formula
Molecular Weight
180.16  g/mol
InChI Key

The prototypical analgesic used in the treatment of mild to moderate pain. It has anti-inflammatory and antipyretic properties and acts as an inhibitor of cyclooxygenase which results in the inhibition of the biosynthesis of prostaglandins. Aspirin also inhibits platelet aggregation and is used in the prevention of arterial and venous thrombosis. (From Martindale, The Extra Pharmacopoeia, 30th ed, p5)
Aspirin is a Nonsteroidal Anti-inflammatory Drug and Platelet Aggregation Inhibitor. The mechanism of action of aspirin is as a Cyclooxygenase Inhibitor. The physiologic effect of aspirin is by means of Decreased Prostaglandin Production and Decreased Platelet Aggregation.
1 2D Structure

2D Structure

2 Identification
2.1 Computed Descriptors
2.1.1 IUPAC Name
2-acetyloxybenzoic acid
2.1.2 InChI
2.1.3 InChI Key
2.1.4 Canonical SMILES
2.2 Other Identifiers
2.2.1 UNII
2.3 Synonyms
2.3.1 MeSH Synonyms

1. 2-(acetyloxy)benzoic Acid

2. Acetylsalicylic Acid

3. Acetysal

4. Acid, Acetylsalicylic

5. Acylpyrin

6. Aloxiprimum

7. Colfarit

8. Dispril

9. Easprin

10. Ecotrin

11. Endosprin

12. Magnecyl

13. Micristin

14. Polopirin

15. Polopiryna

16. Solprin

17. Solupsan

18. Zorprin

2.3.2 Depositor-Supplied Synonyms

1. Acetylsalicylic Acid

2. 50-78-2

3. 2-acetoxybenzoic Acid

4. 2-(acetyloxy)benzoic Acid

5. O-acetylsalicylic Acid

6. Acetylsalicylate

7. O-acetoxybenzoic Acid

8. Acylpyrin

9. Easprin

10. Ecotrin

11. Salicylic Acid Acetate

12. Acenterine

13. Acetophen

14. Polopiryna

15. Acetosal

16. Colfarit

17. O-carboxyphenyl Acetate

18. Acidum Acetylsalicylicum

19. Enterosarein

20. Aceticyl

21. Acetonyl

22. Acetosalin

23. Acetylin

24. Aspergum

25. Aspirdrops

26. Benaspir

27. Measurin

28. Micristin

29. Pharmacin

30. Premaspin

31. Salcetogen

32. Temperal

33. Ecolen

34. Empirin

35. Endydol

36. Rhodine

37. Saletin

38. Rheumintabletten

39. Solprin Acid

40. 2-acetyloxybenzoic Acid

41. Benzoic Acid, 2-(acetyloxy)-

42. Acetisal

43. Acetylsal

44. Aspirine

45. Bialpirina

46. Bialpirinia

47. Claradin

48. Clariprin

49. Entericin

50. Enterophen

51. Enterosarine

52. Globentyl

53. Neuronika

54. Salacetin

55. Solpyron

56. Acesal

57. Acisal

58. Asagran

59. Asteric

60. Cemirit

61. Decaten

62. Duramax

63. Extren

64. Globoid

65. Helicon

66. Idragin

67. Levius

68. Pirseal

69. Rhonal

70. Solfrin

71. Adiro

72. Aspec

73. Aspro

74. Novid

75. Yasta

76. Acetosalic Acid

77. Triple-sal

78. Spira-dine

79. Zorprin

80. Bi-prin

81. Acetilum Acidulatum

82. Acimetten

83. Delgesic

84. Entrophen

85. Persistin

86. 2-carboxyphenyl Acetate

87. Acetilsalicilico

88. Dolean Ph 8

89. A.s.a. Empirin

90. Xaxa

91. Acido Acetilsalicilico

92. Contrheuma Retard

93. Acide Acetylsalicylique

94. Asa

95. Endosprin

96. Kapsazal

97. Bayer

98. Acetylsalicylsaure

99. Aspirin (acetylsalicylic Acid)

100. Solprin

101. Triaminicin

102. Asatard

103. Durlaza

104. Tasprin

105. Nu-seals Aspirin

106. Salicylic Acid, Acetate

107. Acido O-acetil-benzoico

108. Kyselina Acetylsalicylova

109. 2-acetoxybenzenecarboxylic Acid

110. St. Joseph Aspirin For Adults

111. A.s.a.

112. St. Joseph

113. Kyselina 2-acetoxybenzoova

114. Sp 189

115. Acetard

116. Ac 5230

117. Acetyl Salicylate

118. Acetylsalicylsaeure

119. Azetylsalizylsaeure

120. S-211

121. Ecm

122. Chebi:15365

123. 2-(acetyloxy)benzoate

124. Acetylsalicylicum Acidum

125. Nsc-27223

126. O-(acetyloxy)benzoic Acid

127. Nsc-406186

128. Acide 2-(acetyloxy)benzoique

129. Acetylsalicylic Acid (who-ip)

130. R16co5y76e

131. Aspirin Form Ii

132. Component Of Midol

133. Nsc27223

134. Component Of Synirin

135. 8-hour Bayer

136. Component Of Zactirin

137. Bay1019036

138. Component Of Coricidin

139. Component Of Persistin

140. Component Of Robaxisal

141. O-acetoxybenzoate

142. Ncgc00015067-04

143. Acetysal

144. Istopirin

145. Magnecyl

146. Medisyl

147. Polopirin

148. Ronal

149. Bayer Buffered

150. Dsstox_cid_108

151. Aspro Clear

152. Component Of Ascodeen-30

153. Bayer Plus

154. Wln: Qvr Bov1

155. Rheumin Tabletten

156. Acetylsalicylicacid

157. Dsstox_rid_75372

158. Dsstox_gsid_20108

159. Aspirina 03

160. Acetylsalycilic Acid

161. Acetyl Salicylic Acid

162. Component Of Darvon With A.s.a

163. Bayer Aspirin 8 Hour

164. Asaphen

165. Aspalon

166. Asprin

167. Bayer Children's Aspirin

168. Nu-seals

169. Component Of St. Joseph Cold Tablets

170. Aspir-mox

171. Durlaza Er

172. Acetylsalicylsaure [german]

173. Cas-50-78-2

174. Acetoxybenzoic Acid

175. Acetysalicylic Acid

176. 11126-35-5

177. Ain

178. Smr000059138

179. Ascoden-30

180. Benzoicacid, 2-(acetyloxy)-

181. Acetylsalicyclic Acid

182. Ccris 3243

183. Hsdb 652

184. Acide Acetylsalicylique [french]

185. Acido Acetilsalicilico [italian]

186. Kyselina Acetylsalicylova [czech]

187. Acido O-acetil-benzoico [italian]

188. Sr-01000075668

189. Kyselina 2-acetoxybenzoova [czech]

190. Bayer Extra Strength Aspirin For Migraine Pain

191. Einecs 200-064-1

192. Nsc 27223

193. Aspirin [usp:ban:jan]

194. Bayer Enteric 325 Mg Regular Strength

195. Brn 0779271

196. Bay E4465

197. Unii-r16co5y76e

198. Aspropharm

199. Bayer Enteric 81 Mg Adult Low Strength

200. Cardioaspirin

201. Cardioaspirina

202. Acetyonyl

203. Asacard

204. Ascolong

205. Bayer Enteric 500 Mg Arthritis Strength

206. Colsprin

207. Miniasal

208. Salospir

209. Acesan

210. Toldex

211. Ai3-02956

212. 1oxr

213. 2-acetoxybenzoate

214. Aspirin,(s)

215. Aspalon (jan)

216. Durlaza (tn)

217. Easprin (tn)

218. Mfcd00002430

219. Acetyl-salicylic Acid

220. Aspirin Usp-26

221. Acetyl Salicyclic Acid

222. O-(acetyloxy)benzoate

223. Percodan (salt/mix)

224. Ascriptin (salt/mix)

225. Micrainin (salt/mix)

226. 2-acetoxy Benzoic Acid

227. Spectrum_001245

228. 2-acetylsalicyclic Acid

229. Aspirin [vandf]

230. Aspirin [hsdb]

231. Salicylic Acid, Acetyl-

232. Aspirin [jan]

233. Aspirin [mi]

234. Chembl25

235. Aspirin [mart.]

236. Spectrum2_001899

237. Spectrum3_001295

238. Spectrum4_000099

239. Spectrum5_000740

240. Aspirin (jp17/usp)

241. Lopac-a-5376

242. Salycylacetylsalicylic Acid

243. Aspirin [usp-rs]

244. Benzoic Acid, 2-acetoxy-

245. Epitope Id:114151

246. Percodan Demi (salt/mix)

247. Soma Compound (salt/mix)

248. Zinc53

249. Ec 200-064-1

250. Acetylsalicylic Acid, 99%

251. Aspirin Usp (3080)

252. Cid_2244

253. Pravigard Pac (salt/mix)

254. Schembl1353

255. 2-(acetyloxy)-benzoic Acid

256. Aspirin Usp (2080b)

257. Bay-e-4465

258. Acetylsalicylic Acid-[13c]

259. Lopac0_000038

260. Kbiogr_000398

261. Kbiogr_002271

262. Kbioss_001725

263. Kbioss_002272

264. 4-10-00-00138 (beilstein Handbook Reference)

265. Mls001055329

266. Mls001066332

267. Mls001336045

268. Mls001336046

269. Aspirin [orange Book]

270. Bidd:gt0118

271. Divk1c_000555

272. Spectrum1500130

273. Spbio_001838

274. Acetylsalicylic Acid, >=99%

275. Axotal Component Aspirin

276. Azdone Component Aspirin

277. Codoxy Component Aspirin

278. Gtpl4139

279. (non-d)acetylsalicylic Acid-d3

280. Aspirin [usp Monograph]

281. O-acetylsalicylic Acid; Aspirin

282. Dtxsid5020108

283. Acetylsalicylic Acid-carboxy-14c

284. Aggrenox Component Aspirin

285. Bdbm22360

286. Duocover Component Aspirin

287. Excedrin Component Aspirin

288. Fiorinal Component Aspirin

289. Hms501l17

290. Kbio1_000555

291. Kbio2_001725

292. Kbio2_002271

293. Kbio2_004293

294. Kbio2_004839

295. Kbio2_006861

296. Kbio2_007407

297. Kbio3_002149

298. Kbio3_002751

299. Norgesic Component Aspirin

300. Percodan Component Aspirin

301. Q-gesic Component Aspirin

302. Roxiprin Component Aspirin

303. Vicoprin Component Aspirin

304. Yosprala Component Aspirin

305. Empirin With Codeine (salt/mix)

306. Acetylsalicylic Acid, >=99.0%

307. Cmap_000006

308. Component Of Zactirin (salt/mix)

309. Duoplavin Component Aspirin

310. Equagesic Component Aspirin

311. Invagesic Component Aspirin

312. Lanorinal Component Aspirin

313. Micrainin Component Aspirin

314. Ninds_000555

315. Robaxisal Component Aspirin

316. Aspirin Component Of Axotal

317. Aspirin Component Of Azdone

318. Aspirin Component Of Codoxy

319. Hms1920e13

320. Hms2090g03

321. Hms2091k13

322. Hms2233l18

323. Hms3260g17

324. Hms3372n15

325. Hms3656n14

326. Hms3715p19

327. Hms3866l03

328. Hms3885g03

329. Pharmakon1600-01500130

330. Acetylsalicylic Acid [inci]

331. Bcp21790

332. Orphengesic Component Aspirin

333. Str01551

334. Acetylsalicylic Acid; Aspirin

335. Aspirin Component Of Aggrenox

336. Aspirin Component Of Duocover

337. Aspirin Component Of Excedrin

338. Aspirin Component Of Fiorinal

339. Aspirin Component Of Norgesic

340. Aspirin Component Of Percodan

341. Aspirin Component Of Q-gesic

342. Aspirin Component Of Roxiprin

343. Aspirin Component Of Vicoprin

344. Aspirin Component Of Yosprala

345. Synalgos-dc Component Aspirin

346. Tox21_110076

347. Tox21_202117

348. Tox21_300146

349. Tox21_500038

350. Ccg-39490

351. Nsc406186

352. Nsc755899

353. S3017

354. Stl137674

355. Acetylsalicylic Acid [who-dd]

356. Aspirin Component Of Duoplavin

357. Aspirin Component Of Equagesic

358. Aspirin Component Of Invagesic

359. Aspirin Component Of Lanorinal

360. Aspirin Component Of Micrainin

361. Aspirin Component Of Robaxisal

362. Akos000118884

363. Component Of Ascodeen-30 (salt/mix)

364. Mepro-aspirin Component Aspirin

365. Percodan-demi Component Aspirin

366. Pravigard Pac Component Aspirin

367. Soma Compound Component Aspirin

368. Tox21_110076_1

369. Acetylsalicylic Acid [ema Epar]

370. Acetylsalicylicum Acidum [hpus]

371. Aspirin Component Of Orphengesic

372. Cs-2001

373. Db00945

374. Lp00038

375. Nsc-755899

376. Pl-2200

377. Sdccgsbi-0050027.p005

378. Aspirin Component Of Synalgos-dc

379. Bay-1019036

380. Darvon Compound Component Aspirin

381. Idi1_000555

382. Invagesic Forte Component Aspirin

383. Talwin Compound Component Aspirin

384. Acetylsalicylic Acid [green Book]

385. Acetylsalicylic Acid, Analytical Standard

386. Acidum Acetylsalicylicum (who-ip)

387. Ncgc00015067-01

388. Ncgc00015067-02

389. Ncgc00015067-03

390. Ncgc00015067-05

391. Ncgc00015067-06

392. Ncgc00015067-07

393. Ncgc00015067-08

394. Ncgc00015067-09

395. Ncgc00015067-10

396. Ncgc00015067-11

397. Ncgc00015067-12

398. Ncgc00015067-13

399. Ncgc00015067-14

400. Ncgc00015067-24

401. Ncgc00015067-26

402. Ncgc00090977-01

403. Ncgc00090977-02

404. Ncgc00090977-03

405. Ncgc00090977-04

406. Ncgc00090977-05

407. Ncgc00090977-06

408. Ncgc00090977-07

409. Ncgc00254034-01

410. Ncgc00259666-01

411. Ncgc00260723-01

412. Aspirin Component Of Mepro-aspirin

413. Aspirin Component Of Percodan-demi

414. Aspirin Component Of Pravigard Pac

415. Aspirin Component Of Soma Compound

416. Aspirin, Meets Usp Testing Specifications

417. Hy-14654

418. Nci60_002222

419. Orphengesic Forte Component Aspirin

420. Acetylsalicylic Acid [ep Monograph]

421. Sbi-0050027.p004

422. Aspirin Component Of Darvon Compound

423. Aspirin Component Of Invagesic Forte

424. Aspirin Component Of Talwin Compound

425. Ds-017139

426. Unm-0000306102

427. Aspirin Component Of Orphengesic Forte

428. Component Of Darvon With A.s.a (salt/mix)

429. Eu-0100038

430. Ft-0655181

431. Ft-0661360

432. Sw199665-2

433. Carisoprodol Compound Component Aspirin

434. A 5376

435. Acetylsalicylic Acid 1.0 Mg/ml In Acetonitrile

436. C01405

437. D00109

438. E80792

439. Q18216

440. Ab00051918-08

441. Ab00051918_09

442. Ab00051918_10

443. Aspirin Component Of Carisoprodol Compound

444. Arthritis Pain Formula Maximum Strength (salt/mix)

445. Sr-01000075668-1

446. Sr-01000075668-4

447. Sr-01000075668-6

448. Acetylsalicylic Acid, Vetec(tm) Reagent Grade, >=99%

449. Aspirin, British Pharmacopoeia (bp) Reference Standard

450. Clopidogrel/acetylsalicylic Acid Component Aspirin

451. F2191-0068

452. Z234893989

453. Aspirin Component Of Clopidogrel/acetylsalicylic Acid

454. Aspirin, United States Pharmacopeia (usp) Reference Standard

455. D41527a7-a9eb-472d-a7fc-312821130549

456. Acetylsalicylic Acid, European Pharmacopoeia (ep) Reference Standard

457. Acetylsalicylic Acid, Bioreagent, Plant Cell Culture Tested, >=99.0%

458. Acetylsalicylic Acid For Peak Identification, European Pharmacopoeia (ep) Reference Standard

459. Aspirin (acetyl Salicylic Acid), Pharmaceutical Secondary Standard; Certified Reference Material

2.4 Create Date
3 Chemical and Physical Properties
Molecular Weight 180.16 g/mol
Molecular Formula C9H8O4
Hydrogen Bond Donor Count1
Hydrogen Bond Acceptor Count4
Rotatable Bond Count3
Exact Mass180.04225873 g/mol
Monoisotopic Mass180.04225873 g/mol
Topological Polar Surface Area63.6 Ų
Heavy Atom Count13
Formal Charge0
Isotope Atom Count0
Defined Atom Stereocenter Count0
Undefined Atom Stereocenter Count0
Defined Bond Stereocenter Count0
Undefined Bond Stereocenter Count0
Covalently Bonded Unit Count1
4 Drug and Medication Information
4.1 Drug Information
1 of 2  
Drug NameAspirin
PubMed HealthAspirin
Drug ClassesAnalgesic, Antipyretic, Antirheumatic, Central Nervous System Agent, Platelet Aggregation Inhibitor
Drug LabelDistributed by GENUINE FIRST AID600 Clevelad Str Suite 400, Clearwater, FL 33755...
Active IngredientAspirin
Dosage FormCapsule
Market StatusOver the Counter
CompanyPlx Pharma

2 of 2  
Drug NameAspirin
PubMed HealthAspirin
Drug ClassesAnalgesic, Antipyretic, Antirheumatic, Central Nervous System Agent, Platelet Aggregation Inhibitor
Drug LabelDistributed by GENUINE FIRST AID600 Clevelad Str Suite 400, Clearwater, FL 33755...
Active IngredientAspirin
Dosage FormCapsule
Market StatusOver the Counter
CompanyPlx Pharma

4.2 Therapeutic Uses

Anti-Inflammatory Agents, Non-Steroidal; Cyclooxygenase Inhibitors; Fibrinolytic Agents; Platelet Aggregation Inhibitors

National Library of Medicine's Medical Subject Headings online file (MeSH, 1999)

Salicylates are indicated to relieve myalgia, musculoskeletal pain, and other symptoms of nonrheumatic inflammatory conditions such as athletic injuries, bursitis, capsulitis, tendinitis, and nonspecific acute tenosynovitis. /Included in US product labeling/

Thomson/Micromedex. Drug Information for the Health Care Professional. Volume 1, Greenwood Village, CO. 2007., p. 2574

Salicylates are indicated for the symptomatic relief of acute and chronic rheumatoid arthritis, juvenile arthritis, osteoarthritis, and related rheumatic diseases. Aspirin is usually the first agent to be used and may be the drug of choice in patients able to tolerate prolonged therapy with high doses. These agents do not affect the progressive course of rheumatoid arthritis. Concurrent treatment with a glucocorticoid or a disease-modifying antirheumatic agent may be needed, depending on the condition being treated and patient response. /Included in US product labeling/

Thomson/Micromedex. Drug Information for the Health Care Professional. Volume 1, Greenwood Village, CO. 2007., p. 2574

Salicylates are also used to reduce arthritic complications associated with systemic lupus erythematosus. /Salicylates; NOT included in US product labeling/

Thomson/Micromedex. Drug Information for the Health Care Professional. Volume 1, Greenwood Village, CO. 2007., p. 2574

For more Therapeutic Uses (Complete) data for ACETYLSALICYLIC ACID (12 total), please visit the HSDB record page.

4.3 Drug Warning

Aspirin use may be associated with the development of Reye's syndrome in children and teenagers with acute febrile illnesses, especially influenza and varicella. It is recommended that salicylate therapy not be initiated in febrile pediatric or adolescent patients until after the presence of such an illness has been ruled out. Also, it is recommended that chronic salicylate therapy in these patients be discontinued if a fever occurs, and not resumed until it has been determined that an illness that may predispose to Reye's syndrome is not present or has run its course. Other forms of salicylate toxicity may also be more prevalent in pediatric patients, especially children who have a fever or are dehydrated.

Thomson/Micromedex. Drug Information for the Health Care Professional. Volume 1, Greenwood Village, CO. 2007., p. 2577

Especially careful monitoring of the serum salicylate concentration is recommended in pediatric patients with Kawasaki disease. Absorption of aspirin is impaired during the early febrile stage of the disease; therapeutic anti-inflammatory plasma salicylate concentrations may be extremely difficult to achieve. Also, as the febrile stage passes, absorption is improved; salicylate toxicity may occur if dosage is not readjusted.

Thomson/Micromedex. Drug Information for the Health Care Professional. Volume 1, Greenwood Village, CO. 2007., p. 2577

Requirements of Vitamin K may be increased in patients receiving high doses of salicylate. /Salicylate/

Thomson/Micromedex. Drug Information for the Health Care Professional. Volume 1, Greenwood Village, CO. 2007., p. 2578


Gilman, A.G., T.W. Rall, A.S. Nies and P. Taylor (eds.). Goodman and Gilman's The Pharmacological Basis of Therapeutics. 8th ed. New York, NY. Pergamon Press, 1990., p. 650

For more Drug Warnings (Complete) data for ACETYLSALICYLIC ACID (21 total), please visit the HSDB record page.

4.4 Minimum/Potential Fatal Human Dose

The lethal dose of aspirin for an adult is probably in the region of 25 to 30 g but recovery has been achieved by appropriate treatment after the ingestion of twice or thrice this amount.

Reynolds, J.E.F., Prasad, A.B. (eds.) Martindale-The Extra Pharmacopoeia. 28th ed. London: The Pharmaceutical Press, 1982., p. 236

4.5 Drug Indication

**Pain, fever, and inflammation** Acetylsalicylic acid (ASA), in the regular tablet form (immediate-release), is indicated to relieve pain, fever, and inflammation associated with many conditions, including the flu, the common cold, neck and back pain, dysmenorrhea, headache, tooth pain, sprains, fractures, myositis, neuralgia, synovitis, arthritis, bursitis, burns, and various injuries. It is also used for symptomatic pain relief after surgical and dental procedures. The _extra strength_ formulation of acetylsalicylic acid is also indicated for the management migraine pain with photophobia (sensitivity to light) and phonophobia (sensitivity to sound). **Other indications** ASA is also indicated for various other purposes, due to its ability to inhibit platelet aggregation. These include: Reducing the risk of cardiovascular death in suspected cases of myocardial infarction (MI). Reducing the risk of a first non-fatal myocardial infarction in patients, and for reducing the risk of morbidity and mortality in cases of unstable angina and in those who have had a prior myocardial infarction. For reducing the risk of transient ischemic attacks (TIA) and to prevent atherothrombotic cerebral infarction (in conjunction with other treatments). For the prevention of thromboembolism after hip replacement surgery. For decreasing platelet to platelet adhesion following carotid endarterectomy, aiding in the prevention of transient ischemic attacks (TIA). Used for patients undergoing hemodialysis with a silicone rubber arteriovenous cannula inserted to prevent thrombosis at the insertion site. **Important note regarding use of the extended-release formulation** In the setting of acute myocardial infarction, or before percutaneous interventions, the extended-release form of acetylsalicylic acid should not be used. Use immediate-release formulations in scenarios requiring rapid onset of action. The extended-release form is taken to decrease the incidence of mortality and myocardial infarction (MI) for individuals diagnosed with chronic coronary artery disease (CAD), including patients with previous myocardial infarction (MI) or unstable angina or with chronic stable angina. Additionally, the extended-release form is used to decrease the risk of death and recurrent episodes of stroke in patients with a history of stroke or TIA.

FDA Label

5 Pharmacology and Biochemistry
5.1 Pharmacology

**Effects on pain and fever** Acetylsalicylic acid disrupts the production of prostaglandins throughout the body by targeting cyclooxygenase-1 (COX-1) and cyclooxygenase-2 (COX-2). Prostaglandins are potent, irritating substances that have been shown to cause headaches and pain upon injection into humans. Prostaglandins increase the sensitivity of pain receptors and substances such as histamine and bradykinin. Through the disruption of the production and prevention of release of prostaglandins in inflammation, this drug may stop their action at pain receptors, preventing symptoms of pain. Acetylsalicylic acid is considered an antipyretic agent because of its ability to interfere with the production of brain prostaglandin E1. Prostaglandin E1 is known to be an extremely powerful fever-inducing agent. **Effects on platelet aggregation** The inhibition of platelet aggregation by ASA occurs because of its interference with thromboxane A2 in platelets, caused by COX-1 inhibition. Thromboxane A2 is an important lipid responsible for platelet aggregation, which can lead to clot formation and future risk of heart attack or stroke. **A note on cancer prevention** ASA has been studied in recent years to determine its effect on the prevention of various malignancies. In general, acetylsalicylic acid is involved in the interference of various cancer signaling pathways, sometimes inducing or upregulating tumor suppressor genes. Results of various studies suggest that there are beneficial effects of long-term ASA use in the prevention of several types of cancer, including stomach, colorectal, pancreatic, and liver cancers. Research is ongoing.

5.2 MeSH Pharmacological Classification


Drugs that are used to reduce body temperature in fever. (See all compounds classified as Antipyretics.)

Cyclooxygenase Inhibitors

Compounds or agents that combine with cyclooxygenase (PROSTAGLANDIN-ENDOPEROXIDE SYNTHASES) and thereby prevent its substrate-enzyme combination with arachidonic acid and the formation of eicosanoids, prostaglandins, and thromboxanes. (See all compounds classified as Cyclooxygenase Inhibitors.)

Platelet Aggregation Inhibitors

Drugs or agents which antagonize or impair any mechanism leading to blood platelet aggregation, whether during the phases of activation and shape change or following the dense-granule release reaction and stimulation of the prostaglandin-thromboxane system. (See all compounds classified as Platelet Aggregation Inhibitors.)

Anti-Inflammatory Agents, Non-Steroidal

Anti-inflammatory agents that are non-steroidal in nature. In addition to anti-inflammatory actions, they have analgesic, antipyretic, and platelet-inhibitory actions. They act by blocking the synthesis of prostaglandins by inhibiting cyclooxygenase, which converts arachidonic acid to cyclic endoperoxides, precursors of prostaglandins. Inhibition of prostaglandin synthesis accounts for their analgesic, antipyretic, and platelet-inhibitory actions; other mechanisms may contribute to their anti-inflammatory effects. (See all compounds classified as Anti-Inflammatory Agents, Non-Steroidal.)

Fibrinolytic Agents

Fibrinolysin or agents that convert plasminogen to FIBRINOLYSIN. (See all compounds classified as Fibrinolytic Agents.)

5.3 FDA Pharmacological Classification
5.3.1 Active Moiety
5.3.2 FDA UNII
5.3.3 Pharmacological Classes
Blood Coagulation Factor [EPC]; Calcium [CS]; Cations, Divalent [CS]; Cyclooxygenase Inhibitors [MoA]; Decreased Platelet Aggregation [PE]; Decreased Prostaglandin Production [PE]; Increased Coagulation Factor Activity [PE]; Nonsteroidal Anti-inflammatory Drug [EPC]; Platelet Aggregation Inhibitor [EPC]; Anti-Inflammatory Agents, Non-Steroidal [CS]
5.4 ATC Code


S76 | LUXPHARMA | Pharmaceuticals Marketed in Luxembourg | Pharmaceuticals marketed in Luxembourg, as published by d'Gesondheetskeess (CNS, la caisse nationale de sante, www.cns.lu), mapped by name to structures using CompTox by R. Singh et al. (in prep.). List downloaded from https://cns.public.lu/en/legislations/textes-coordonnes/liste-med-comm.html. Dataset DOI:10.5281/zenodo.4587355

A - Alimentary tract and metabolism

A01 - Stomatological preparations

A01A - Stomatological preparations

A01AD - Other agents for local oral treatment

A01AD05 - Acetylsalicylic acid

B - Blood and blood forming organs

B01 - Antithrombotic agents

B01A - Antithrombotic agents

B01AC - Platelet aggregation inhibitors excl. heparin

B01AC06 - Acetylsalicylic acid

N - Nervous system

N02 - Analgesics

N02B - Other analgesics and antipyretics

N02BA - Salicylic acid and derivatives

N02BA01 - Acetylsalicylic acid

5.5 Absorption, Distribution and Excretion


Absorption is generally rapid and complete following oral administration but absorption may be variable depending on the route, dosage form, and other factors including but not limited to the rate of tablet dissolution, gastric contents, gastric emptying time, and gastric pH. **Detailed absorption information** When ingested orally, acetylsalicylic acid is rapidly absorbed in both the stomach and proximal small intestine. The non-ionized acetylsalicylic acid passes through the stomach lining by passive diffusion. Ideal absorption of salicylate in the stomach occurs in the pH range of 2.15 - 4.10. Intestinal absorption of acetylsalicylic acid occurs at a much faster rate. At least half of the ingested dose is hydrolyzed to salicylic acid in the first-hour post-ingestion by esterases found in the gastrointestinal tract. Peak plasma salicylate concentrations occur between 1-2 hours post-administration.

Route of Elimination

Excretion of salicylates occurs mainly through the kidney, by the processes of glomerular filtration and tubular excretion, in the form of free salicylic acid, salicyluric acid, and, additionally, phenolic and acyl glucuronides. Salicylate can be found in the urine soon after administration, however, the entire dose takes about 48 hours to be completely eliminated. The rate of salicylate is often variable, ranging from 10% to 85% in the urine, and heavily depends on urinary pH. Acidic urine generally aids in reabsorption of salicylate by the renal tubules, while alkaline urine increases excretion. After the administration of a typical 325mg dose, the elimination of ASA is found to follow first order kinetics in a linear fashion. At high concentrations, the elimination half-life increases.

Volume of Distribution

This drug is distributed to body tissues shortly after administration. It is known to cross the placenta. The plasma contains high levels of salicylate, as well as tissues such as spinal, peritoneal and synovial fluids, saliva and milk. The kidney, liver, heart, and lungs are also found to be rich in salicylate concentration after dosing. Low concentrations of salicylate are usually low, and minimal concentrations are found in feces, bile, and sweat.


The clearance rate of acetylsalicylic acid is extremely variable, depending on several factors. Dosage adjustments may be required in patients with renal impairment. The extended-release tablet should not be administered to patients with eGFR of less than 10 mL/min.

The materno-fetal transfer of salicylic acid and its distribution in the fetal organism was investigated in women of early pregnancy. Acetylsalicylic acid was administered orally in a single dose or in repeated doses at different times before legal interruption. The mean passage rates were about 6-15%. They were independent of the maternal serum concentrations of salicylic acid. The distribution of salicylic acid on the fetal liver, intestine, kidneys, lungs and brain was different. All fetal organs (9th to 15th week of gestation) studied exhibit an acetylsalicylic acid-splitting esterase activity. The esterase activity of the fetal liver was about 30% of the hydrolytic activity of the adult liver. The esterase activity was mainly located in the 105 000 X g-supernatant of cell homogenates.

PMID:6651815 Amon I et al; Biomed Biochim Acta 42 (7-8): 997-1004 (1983)

Approximately 80-100% of an oral dose of aspirin is absorbed from the GI tract. However, the actual bioavailability of the drug as unhydrolyzed aspirin is lower since aspirin is partially hydrolyzed to salicylate in the GI mucosa during absorption and on first pass through the liver. There are relatively few studies of the bioavailability of unhydrolyzed aspirin. In one study in which aspirin was administered IV and as an oral aqueous solution, it was shown that the solution was completely absorbed but only about 70% reached the systemic circulation as unhydrolyzed aspirin. In another study in which aspirin was administered IV and orally as capsules, only about 50% of the oral dose reached the systemic circulation as unhydrolyzed aspirin. There is some evidence that the bioavailability of unhydrolyzed aspirin from slowly absorbed dosage forms (e.g., enteric-coated tablets) may be substantially decreased. Food does not appear to decrease the bioavailability of unhydrolyzed aspirin or salicylate; however, absorption is delayed and peak serum aspirin or salicylate concentration may be decreased. There is some evidence that absorption of salicylate following oral administration may be substantially impaired or is highly variable during the febrile phase of Kawasaki disease.

McEvoy, G.K. (ed.). American Hospital Formulary Service. AHFS Drug Information. American Society of Health-System Pharmacists, Bethesda, MD. 2007., p. 2036

A 52 year-old woman ingested approximately 300 tablets (325 mg) of aspirin in a suicide attempt. ... The concentrations of salicylic acid in heart and femoral blood were 1.1 mg/mL and 1.3 mg/mL, respectively; the results were far higher than the lethal level. The concentration of salicylic acid was 0.3-0.4 mg/g in brain, 0.9-1.4 mg/g in lung, 0.6-0.8 mg/g in liver and 0.9 mg/mL in kidney.

PMID:18044220 Ihama Y t al; Chudoku Kenkyu 20 (4): 375-80 (2007)

The study was undertaken to determine the distribution of aspirin and its metabolites in the semen of humans after an oral dose of aspirin. Each of seven healthy male volunteers was given a single oral dose of 975 mg of aspirin on an empty stomach together with 200 mL of water. Timed samples of blood and semen were obtained from each subject, and the concentrations of aspirin, salicylic acid, and salicyluric acid determined by a specific high-performance liquid chromatographic assay. The mean peak concentration of aspirin was 6.5 micrograms/mL in plasma (range, 4.9-8.9 micrograms/mL), reached in 26 minutes (range, 13-33 minutes). The half-life of aspirin was 31 minutes. The concentration ratio of aspirin (semen/plasma) was 0.12 (except for one subject in whom it was 0.025). The mean peak concentration of salicylate in plasma was 49 micrograms/mL (range, 42-62 micrograms/mL), reached in 2.5 hours (range, 2.0-2.8 hours). Salicylate distributed rapidly into semen and maintained a concentration ratio (semen/plasma) of 0.15. Salicyluric acid (the glycine conjugate of salicylic acid) was found in the semen. Its high concentration in some subjects' semen (four times the concurrent plasma concentration) was attributed to contamination of semen sample with residual urine, containing salicylurate, in the urethra of those who urinated after the dose of aspirin. Possible side effects of aspirin and salicylate in semen include adverse effects on fertility, male-medicated teratogenesis, dominant lethal mutations, and hypersensitivity reactions in the recipients.

PMID:3680588 Kershaw RA et al; J Clin Pharmacol 27 (4): 304-9 (1987)

For more Absorption, Distribution and Excretion (Complete) data for ACETYLSALICYLIC ACID (12 total), please visit the HSDB record page.

5.6 Metabolism/Metabolites

Acetylsalicylic acid is hydrolyzed in the plasma to salicylic acid. Plasma concentrations of aspirin following after administration of the extended-release form are mostly undetectable 4-8 hours after ingestion of a single dose. Salicylic acid was measured at 24 hours following a single dose of extended-release acetylsalicylic acid. Salicylate is mainly metabolized in the liver, although other tissues may also be involved in this process. The major metabolites of acetylsalicylic acid are salicylic acid, salicyluric acid, the ether or phenolic glucuronide and the ester or acyl glucuronide. A small portion is converted to gentisic acid and other hydroxybenzoic acids.

Acetylsalicylic acid is hydrolyzed in the stomach and in blood to salicylic acid and acetic acid; ... .

International Programme on Chemical Safety; Poisons Information Monograph: Acetylsalicylic Acid (PIM 006) (1991) Available from, as of March 10, 2008: https://www.inchem.org/pages/pims.html


The Chemical Society. Foreign Compound Metabolism in Mammals. Volume 2: A Review of the Literature Published Between 1970 and 1971. London: The Chemical Society, 1972., p. 183

A 52 year-old woman ingested approximately 300 tablets (325 mg) of aspirin in a suicide attempt. /Investigators/ analyzed the concentrations of salicylic acid (SA) and salicyluric acid (SUA) in body fluids and organs using a modified previous high-performance liquid chromatographic method. The concentrations of SA in heart and femoral blood were 1.1 mg/mL and 1.3 mg/mL, respectively; the results were far higher than the lethal level. The concentration of SA was 0.3-0.4 mg/g in brain, 0.9-1.4 mg/g in lung, 0.6-0.8 mg/g in liver and 0.9 mg/mL in kidney.

PMID:18044220 Ihama Y et al; Chudoku Kenkyu 20 (4): 375-80 (2007)

5.7 Biological Half-Life

The half-life of ASA in the circulation ranges from 13 - 19 minutes. Blood concentrations drop rapidly after complete absorption. The half-life of the salicylate ranges between 3.5 and 4.5 hours.

15 to 20 minutes (for intact molecule); rapidly hydrolyzed to salicylate. In breast milk (as salicylate): 3.8 to 12.5 hours (average 7.1 hours) following a single 650 mg dose of aspirin.

Thomson/Micromedex. Drug Information for the Health Care Professional. Volume 1, Greenwood Village, CO. 2007., p. 2576

Cats are deficient in glucuronyl transferase and have a prolonged excretion of aspirin (the half-life in cats is 37.5 hr).

Kahn, C.M. (Ed.); The Merck Veterinary Manual 9th ed. Merck & Co. Whitehouse Station, NJ. 2005, p. 2528

5.8 Mechanism of Action

Acetylsalicylic acid (ASA) blocks prostaglandin synthesis. It is non-selective for COX-1 and COX-2 enzymes. Inhibition of COX-1 results in the inhibition of platelet aggregation for about 7-10 days (average platelet lifespan). The acetyl group of acetylsalicylic acid binds with a serine residue of the cyclooxygenase-1 (COX-1) enzyme, leading to irreversible inhibition. This prevents the production of pain-causing prostaglandins. This process also stops the conversion of arachidonic acid to thromboxane A2 (TXA2), which is a potent inducer of platelet aggregation. Platelet aggregation can result in clots and harmful venous and arterial thromboembolism, leading to conditions such as pulmonary embolism and stroke. It is important to note that there is 60% homology between the protein structures of COX-1 and COX-2. ASA binds to serine 516 residue on the active site of COX-2 in the same fashion as its binding to the serine 530 residue located on the active site of COX-1. The active site of COX-2 is, however, slightly larger than the active site of COX-1, so that arachidonic acid (which later becomes prostaglandins) manages to bypass the aspirin molecule inactivating COX-2. ASA, therefore, exerts more action on the COX-1 receptor rather than on the COX-2 receptor. A higher dose of acetylsalicylic acid is required for COX-2 inhibition.

Produce analgesia through a peripheral action by blocking pain impulse generation and via a central action, possibly in the hypothalamus. The peripheral action may predominate and probably involves inhibition of the synthesis or prostaglandins, and possibly inhibition of the synthesis and/or actions of other substances, which sensitize pain receptors to mechanical or chemical stimulation. /Salicylates/

Thomson/Micromedex. Drug Information for the Health Care Professional. Volume 1, Greenwood Village, CO. 2007., p. 2575

May produce antipyresis by acting centrally on the hypothalamic heat-regulating center to produce peripheral vasodilation resulting in increased cutaneous blood flow, sweating, and heat loss. The central action may involve inhibition of prostaglandin synthesis in the hypothalamus; however, there is some evidence that fevers caused by endogenous pyrogens that do not act via a prostaglandin mechanism may also respond to salicylate therapy. /Salicylates/

Thomson/Micromedex. Drug Information for the Health Care Professional. Volume 1, Greenwood Village, CO. 2007., p. 2575


Evaluations of Drug Interactions. 2nd ed. and supplements. Washington, DC: American Pharmaceutical Assn., 1976, 1978., p. 341

Aspirin acetylates prostaglandin endoperoxide synthase (prostaglandin G/H-synthase) and irreversibly inhibits its cyclooxygenase (COX) activity. The enzyme catalyzes the conversion of arachidonic acid to PGH2, the first committed step in prostanoid biosynthesis. Two isoforms of prostaglandin endoperoxide synthase exist, PGHS-1 and PGHS-2 (also referred to as COX-1 and COX-2, respectively). PGHS-1 (COX-1) is expressed constitutively in most cell types, including platelets. PGHS-2 (COX-2) is undetectable in most mammalian cells, but its expression can be induced rapidly in response to mitogenic and inflammatory stimuli. Aspirin is a relatively selective inhibitor of platelet PGHS-1 (cyclooxygenase-1, COX-1). The existence of 2 isoenzymes with different aspirin sensitivities, coupled with extremely different recovery rates of their cyclooxygenase (COX) activity following inactivation by aspirin, at least partially explains the different dosage requirements and durations of aspirin effects on platelet function versus the drug's analgesic and anti-inflammatory effects. Human platelets and vascular endothelial cells process PGH2 to produce thromboxane A2 and prostacyclin (epoprostenol, PGI2), respectively. Thromboxane A2 induces platelet aggregation and vasoconstriction, while prostacyclin inhibits platelet aggregation and induces vasodilation. Aspirin is antithrombotic in a wide range of doses inhibiting thromboxane A2 and prostacyclin.

McEvoy, G.K. (ed.). American Hospital Formulary Service. AHFS Drug Information. American Society of Health-System Pharmacists, Bethesda, MD. 2007., p. 2035

For more Mechanism of Action (Complete) data for ACETYLSALICYLIC ACID (12 total), please visit the HSDB record page.

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