PRIMACOR
Clinical safety rating: caution
Comprehensive clinical and safety monograph for PRIMACOR (PRIMACOR).
Phosphodiesterase-3 (PDE-3) inhibitor, increasing cAMP in cardiac and vascular smooth muscle, leading to positive inotropy and vasodilation.
| Metabolism | Hepatic via conjugation (glucuronidation), with minor renal excretion of unchanged drug. |
| Excretion | Primarily renal (60-70% unchanged), with minor biliary/fecal (15-20%). |
| Half-life | Terminal elimination half-life is 2-4 hours in patients with normal renal function; prolonged to 8-12 hours in severe renal impairment. |
| Protein binding | 80-90% bound primarily to albumin. |
| Volume of Distribution | 0.3-0.5 L/kg, indicating distribution primarily in extracellular fluid. |
| Bioavailability | Oral: approximately 70-80% due to first-pass metabolism. |
| Onset of Action | Intravenous: 2-5 minutes; oral: 30-60 minutes. |
| Duration of Action | Intravenous: 30-60 minutes; oral: 4-6 hours. Duration is dose-dependent and influenced by renal function. |
| Action Class | Phosphodiesterase-III inhibitors (HF) |
| Brand Substitutes | Myolong 10mg Injection, Renota 10mg Injection, Milrilact 10mg Injection, Milron 10mg Injection, Milnone 10mg Injection |
IV bolus: 0.75 mg/kg over 10-15 minutes, followed by continuous IV infusion of 5-10 mcg/kg/min. Maximum daily dose: 40 mg.
| Dosage form | INJECTABLE |
| Renal impairment | CrCl 30-50 mL/min: reduce infusion to 3.3-6.7 mcg/kg/min; CrCl <30 mL/min: reduce infusion to 2.5-5 mcg/kg/min. |
| Liver impairment | Child-Pugh Class B or C: reduce infusion by 50% (starting at 2.5-5 mcg/kg/min) and titrate cautiously. |
| Pediatric use | Loading dose: 50-75 mcg/kg IV over 15 min; maintenance: 5-10 mcg/kg/min continuous IV. Safety and efficacy not established in patients <6 months. |
| Geriatric use | Consider lower initial infusion rates (3-6 mcg/kg/min) due to age-related renal function decline; monitor for hypotension and arrhythmias. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for PRIMACOR (PRIMACOR).
| Breastfeeding | It is not known whether milrinone is excreted in human breast milk. Because many drugs are excreted in milk, caution is advised. M/P ratio: not available. A decision should be made to discontinue nursing or discontinue the drug, taking into account the importance of the drug to the mother. |
| Teratogenic Risk | Primacor (milrinone) is a Pregnancy Category C drug. Animal studies have shown embryotoxicity and fetotoxicity at doses 2-4 times the human dose. There are no adequate and well-controlled studies in pregnant women. First trimester: Potential for fetal harm, but specific malformation patterns not established. Second and third trimesters: Risk of maternal hypotension and tachyarrhythmias may reduce uteroplacental blood flow, leading to fetal hypoxia. |
■ FDA Black Box Warning
Increased mortality in long-term therapy of heart failure; not recommended for chronic use.
| Serious Effects |
Hypersensitivity to milrinone or any component, acute myocardial infarction, severe aortic or pulmonic valvular disease, obstructive hypertrophic cardiomyopathy.
| Precautions | Hypotension, tachyarrhythmias (e.g., ventricular ectopy, nonsustained VT), thrombocytopenia, electrolyte disturbances (hypokalemia), exacerbation of myocardial ischemia. |
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| Fetal Monitoring | Monitor maternal blood pressure, heart rate, and ECG continuously during infusion. Assess fluid and electrolyte status, renal function, and platelet counts due to risk of thrombocytopenia. Monitor fetal heart rate and uterine activity if used in peripartum period. |
| Fertility Effects | No adequate reproductive studies in humans. In animal studies, no impairment of fertility was observed at doses up to 2.5 times the human dose. |