1.1. Adults

Platelet aggregation inhibitors (PAIs) are FDA-approved to reduce thrombotic cardiovascular events in patients with a history of ischemic stroke, or to prevent stroke in patients with predisposing factors for atherosclerosis or symptomatic cerebrovascular disease. Cilostazol is FDA approved to reduce symptoms of intermittent claudication. PAIs work by interfering with pathways that promote normal platelet function: inhibiting cyclooxygenase-1 (e.g., aspirin); inhibiting adenosine uptake into platelets, resulting in increased cyclic-3’,5’-adenosine monophosphate (cAMP) and adenosine levels (e.g., dipyridamole); inhibiting the adenosine diphosphate (ADP) P2Y12 receptor on the platelet surface and blocking activation of the glycoprotein GP IIb/IIIa complex (e.g., clopidogrel, prasugrel, ticagrelor); or inhibiting phosphodiesterase III (e.g., cilostazol) [1-8].

Aspirin is also available as combination therapy with dipyridamole, pairing two antiplatelet agents with different mechanisms of action for secondary stroke prevention.1,2,8 Maximum recommended adult dosages for PAIs are summarized in Tables 1 and 2. Medication profiles identifying patients prescribed dosages exceeding these recommendations will be reviewed.

Table 1. Maximum Daily Adult Dosages for PAIs – Monotherapy [1-7]
Drug NameDosage Form/StrengthTreatment IndicationMaximum Recommended Dosage
cilostazol (generics)50 mg, 100 mg tabletsintermittent claudication100 mg twice daily
clopidogrel (Plavix, generics)75 mg, 300 mg tabletsACS, including UA/NSTEMI and STEMIInitial: 300 mg loading dose, followed by 75 mg once daily for up to 12 months in combination with aspirin, followed by aspirin indefinitely
  Rate reduction of MI and stroke in patients with recent MI or stroke, or established peripheral vascular disease75 mg/day
dipyridamole (generics)25 mg, 50 mg, 75 mg tabletsprevention of postoperative thrombotic complications in patients with prosthetic heart valves400 mg/day (divided doses, in combination with warfarin)
prasugrel (Effient, generics)5 mg, 10 mg tabletsACS in patients to be managed with PCIfollowing a 60 mg loading dose, 10 mg/day+ in combination with aspirin
ticagrelor (Brilinta)60 mg, 90 mg tabletsreduce risk of death, MI, and stroke in patients with ACS, history of MI, or acute ischemic stroke/ high risk transient ischemic attackfollowing a 180 mg loading dose, 90 mg twice daily^ in combination with aspirin
  reduce risk of first MI or stroke in patients with CAD at high risk of events60 mg twice daily in combination with aspirin

Legend:

  • ACS = acute coronary syndrome
  • CAD = coronary artery disease
  • MI = myocardial infarction
  • NSTE-ACS = non-ST-elevation acute coronary syndrome
  • NSTEMI = non-ST-elevation myocardial infarction
  • PAD = peripheral arterial disease
  • PCI = percutaneous coronary intervention
  • STEMI = ST-elevation myocardial infarction
  • TIA = transient ischemic attack
  • UA = unstable angina
  • + patients 75 years or older or weigh less than 60 kg may use prasugrel 5 mg/day as maintenance therapy in combination with aspirin to reduce bleeding risk
  • ^ ticagrelor dosages are decreased to 60 mg twice daily after 12 months
Table 2. Maximum Daily Adult Dosages for PAIs – Combination Therapy1,2,9,10
Drug NameDosage Form/ StrengthTreatment IndicationMaximum Recommended Dosage
dipyridamole/aspirin (generics)200 mg/25 mg extended-release capsulesecondary stroke prevention200 mg/25 mg twice daily

1.2. Pediatrics

Dipyridamole is FDA-approved for use in pediatric patients 12 years of age and older as adjunctive therapy to prevent thromboembolism following cardiac valve replacement. The maximum recommended dose is 100 mg four times daily in combination with warfarin [1,2,5]. Dosages exceeding these recommendations will be reviewed.

Cilostazol, prasugrel, ticagrelor, and dipyridamole/aspirin are not recommended for use in pediatric patients as safety and efficacy have not been established for these agents in this patient population [1-3,6-8]. Although not FDA-approved, clopidogrel has effectively been used in pediatric patients to reduce thrombosis risk in infants and children with select types of heart disease, or as an alternative in patients with Kawasaki disease or ischemic stroke when aspirin is not tolerated.