Dipyridamole
Persantine · Aggrenox (with ASA)
Phosphodiesterase inhibitor / adenosine reuptake inhibitor — antiplatelet + vasodilator
Inhibits platelet PDE (↑ cAMP) and adenosine reuptake (↑ adenosine → vasodilation). Weak antiplatelet; also a coronary vasodilator used in stress testing.
Indications
- •Secondary stroke prevention (with ASA — Aggrenox)
- •Pharmacologic cardiac stress testing
- •Mechanical valve adjunct (historical)
Dosing
| Context | Adult | Pediatric |
|---|---|---|
| Stroke prevention | Aggrenox (ASA 25 mg / ER dipyridamole 200 mg) PO BID | — |
| Stress test | 0.142 mg/kg/min IV × 4 min | — |
Pharmacokinetics
Oral onset slow; IV (stress) effect within minutes — reverse with aminophylline.
Side effects
- !Headache (common)
- !Coronary steal (angina during stress test)
- !Hypotension, flushing
Contraindications
- ×Active bronchospasm (IV stress — adenosine effect)
- ×Unstable angina/recent MI (IV)
Clinical pearls
- ★IV dipyridamole stress test is REVERSED with aminophylline (adenosine antagonist).
- ★Coronary steal mechanism = the basis of stress testing (dilates normal vessels, 'steals' from stenotic beds).
Other drugs in Antiplatelets
- Aspirin
Irreversibly acetylates COX-1 → blocks thromboxane A2 for the platelet's lifespan (~7–10 days). Antiplatelet effect at low dose; analgesic/anti-inflammatory at high dose.
- Clopidogrel
Prodrug → active metabolite (CYP2C19) irreversibly blocks the platelet P2Y12 ADP receptor for the platelet lifespan.
- Prasugrel
Prodrug → active metabolite irreversibly blocks P2Y12. More potent + more consistent than clopidogrel (not CYP2C19-limited), but more bleeding.
- Ticagrelor
Directly and REVERSIBLY inhibits P2Y12 (not a prodrug, not thienopyridine). Faster onset/offset than clopidogrel.
- Ticlopidine
Irreversibly blocks P2Y12. Largely replaced by clopidogrel due to hematologic toxicity.
- Abciximab
Fab fragment that irreversibly blocks the platelet GP IIb/IIIa receptor → prevents fibrinogen cross-linking (final common pathway of aggregation).
- Eptifibatide
Reversibly blocks GP IIb/IIIa (final common pathway of platelet aggregation). Short-acting.
Suggested reading
- •Miller's Anesthesia, 9e
- •FDA package insert
- •ASRA regional anesthesia in the anticoagulated patient guidelines, 2018
