Mechanism of Action
- Local fibrinolysis by binding to fibrin, converts entrapped plasminogen to plasmin
Oral Pharmacokinetics
- Half-Life: ~2-4.5 hours
- Metabolism: Renal
- Onset: ~within 10 min.
- Duration: Platelet life-span (~5-7 days)
Rectal Pharmacokinetics
- Half-Life: ~4.5-9 h
- Metabolism: Renal
- Onset: ~4-5 hours
- Duration: Platelet life-span (~5-7 days)
Dosing – Pediatric
- For antiplatelet effects, pediatric studies have not been performed with doses derived from adult studies (e.g., arterial ischemic stroke prophylaxis)
- Oral: 1-5 mg/kg/dose once daily (in general max 81 mg/dose)
- Pediatric studies have not been performed with doses derived from adult studies
Initiating Therapy
| Administration: Take with water, food, or milk to decrease GI upset. Doses are typically rounded to a convenient amount (e.g., ¼ of 81 mg tablet). |
|
| Chewable (Immediate release) | Can cut, crush, chew. |
| Capsule (Immediate release) | Swallow whole; do NOT cut, crush, or chew. Take with full glass of water. |
| Enteric-coated (Immediate release) | Absorption can be delayed and/or decreased. Do NOT crush or chew enteric-coated tablets. Should be swallowed whole. |
| Rectal | Remove suppository from plastic packet and insert into rectum as far as possible. |
Monitoring
Routine antiplatelet testing is not required for monitoring of aspirin.
Dosage Forms
Aspirin is available in oral or rectal forms.
Safety Precautions
Renal impairment: There are no recommendations in the manufacturer’s labeling, but consider the following:
- GFR >/= 10 mL/minute/1.73 m2: no dosage adjustment necessary
- GFR < 10 mL/minute/1.73 m2: avoid use
- Peritoneal dialysis: avoid use
- Intermittent hemodialysis: administer daily dose after dialysis session on dialysis days (50-100% dialyzable and concentration dependent with higher salicylate concentration being more readily dialyzable)
- CRRT: No dosage adjustment necessary, monitor serum concentrations
Hepatic impairment: Avoid use in severe liver disease
Drug-Drug interactions:
- Concurrent NSAID use may antagonize antiplatelet effects, especially if taken before aspirin.
- Concurrent antacid use leads to increased gastric pH which can decrease aspirin absorption.
- Check for drug-drug interactions.
Warnings
- Children or teenagers recovering from chickenpox or flu-like symptoms should hold aspirin therapy in general until recovered.
- Changes in behavior (along with nausea or vomiting) may be an early sign of Reye syndrome.
