2-(acetyloxy)-benzoic acid

Absorption
Rapidly and completely absorbed. T max is 1 to 2 h (salicylic acid).

Distribution
Widely distributed to all tissues and fluids including CNS, breast milk, and fetal tissues. Approximately 90% of salicylate is protein bound at concentrations of less than 100 mcg/mL and approximately 75% is bound at concentrations of more than 400 mcg/mL.

Metabolism
Rapidly hydrolyzed to salicylic acid (active). Salicylic acid is conjugated in the liver to the metabolites.

Elimination
Salicylic acid plasma t ½ is approximately 6 h but may exceed 20 h in higher doses. The t ½ is approximately 15 to 20 min for aspirin. Elimination follows zero order kinetics. Renal elimination of unchanged drug depends on urine pH. A pH of more than 6.5 increases renal Cl of free salicylate from less than 5% to more than 80%.

Alcohol
May increase risk of GI ulceration and prolong bleeding time.

Antacids, urinary alkalinizers, and corticosteroids
May decrease aspirin levels.

Anticoagulants, oral and heparin
May increase risk of bleeding.

Carbonic anhydrase inhibitors (eg, acetohexamide), methotrexate, valproic acid
May increase levels of these drugs.

Probenecid, sulfinpyrazone
May decrease uricosuric effect.

Sulfonylureas, insulin
Aspirin (more than 2 g/day) may potentiate glucose lowering.

1.有氣喘的病人
2.自懷孕的第6個月起
3.對salicylates或有類似活性之物質過敏者,特別是非類固醇類抗發炎藥物
4.近期有胃潰瘍或十二指腸潰瘍者
5.有任何先天或後天出血性疾病者
6.有出血危險者
7.併用口服methotrexate,且其每週劑量等於或大於15mg者
8.併用口服抗凝血劑者,且當服用salicylate為高劑量時(每日劑量超過3000mg)