Aspirin/Acetylsalicylic acid
Class: Non-steroidal anti-inflammatory drug (NSAID)
Mechanism of action
Non-selective, irreversible inhibitor of the Cyclooxygenase enzymes (COX-1 & COX-2)
Prevents conversion of arachidonic acid into Prostaglandins (PGs) & Thromboxane (TXA2)
↓ PGs: ↓ pain, fever, and inflammation
↓ TXA2: Inhibits platelet aggregation
Therapeutic uses
Analgesic- For headache including mild migraine, backache, myalgia, joint pain, pulled muscle, toothache, neuralgias and dysmenorrhea
Acute Rheumatic fever
Rheumatoid arthritis (Anti-inflammatory dose 3-5 g/day)
Post MI & post stroke (Anti platelet dose - 60–150 mg/day)
Prevention of Preeclampsia
Treat Familial colonic polyposis and prevent colon cancer
Prevents flushing upon nicotinic acid ingestion
Adverse effects
Nausea, vomiting, epigastric distress, occult blood loss in stools
Gastric mucosal damage and peptic ulceration: MOST IMPORTANT ADVERSE EFFECT
Hypersensitivity and idiosyncrasy- Infrequent, includes rashes, fixed drug eruption, urticaria, rhinorrhea, angioedema, asthma and anaphylactoid reaction.
Salicylism- syndrome produced by Anti-inflammatory doses (3–5 g/day); characterized by dizziness, tinnitus, vertigo, reversible impairment of hearing and vision, excitement, hyperventilation and electrolyte imbalance.
Reye’s syndrome- Rare; causes rapid brain swelling & liver failure; affects children recovering from viral infections
Acute salicylate poisoning- more common in children
Drug interactions of Aspirin
Warfarin/Methotrexate/Phenytoin + Aspirin -------- TOXICITY (OVERDOSE) & BLEEDING IN PATIENTS ON WARFARIN
Probenecid + Aspirin --------- GOUT FLARE UP (↓ URIC ACID EXCRETION)
Diuretics + Aspirin ------- FLUID RETENTION + ↓ BP CONTROL
Precautions and Contraindications
Aspirin is contraindicated in patients with Peptic ulcer, bleeding tendencies, children suffering from viral infections & chronic liver disease.
Avoid Aspirin in G-6PD deficient individuals, during pregnancy & lactation, diabetes, congestive heart failure & juvenile rheumatoid arthritis
Aspirin should be stopped 1 week before elective surgery.
Exam pearls
Aspirin: Less potent & efficacious analgesic than Morphine.
Aspirin + Paracetamol/Codeine = ADDITIVE DRUG COMBINATION
Achlorhydria ↓ Aspirin absorption
Teratogenic effect of Aspirin ---- Premature closure of ductus arteriosus
Aspirin delay the initiation of labor and also prolong its duration
Ibuprofen + low dose Aspirin – Prevent COX inhibition by Aspirin — abolishes the antiplatelet and cardioprotective effect of Aspirin
Nimesulide — Choice of NSAID in patients with Aspirin induced bronchospasm
MBH/PS
