REGITINE
Clinical safety rating: caution
Comprehensive clinical and safety monograph for REGITINE (REGITINE).
Competitive alpha-adrenergic receptor antagonist, blocking catecholamine-induced vasoconstriction and causing peripheral vasodilation.
| Metabolism | Primarily hepatic metabolism via unknown pathways; significant first-pass effect. |
| Excretion | Primarily renal (approximately 10% unchanged, remainder as metabolites) with a small fraction in bile/fecal excretion. |
| Half-life | Terminal elimination half-life is approximately 2-3 hours; clinical context: short half-life necessitates repeated dosing for sustained alpha-blockade in pheochromocytoma management. |
| Protein binding | Approximately 30-40% bound to albumin. |
| Volume of Distribution | Vd approximately 1 L/kg, indicating extensive distribution into tissues. |
| Bioavailability | Intravenous: 100% (only route of clinical relevance; oral absorption is poor and unreliable). |
| Onset of Action | Intravenous: 2-5 minutes after injection. |
| Duration of Action | Intravenous: 10-15 minutes after a single dose; clinical note: short duration limits its use to acute hypertensive episodes. |
Intravenous: 5-10 mg IV push initially, then 2-5 mg IV every 1-2 hours as needed to control hypertension or catecholamine excess. For prevention or control of hypertensive episodes during pheochromocytoma surgery: 2-5 mg IV administered 1-2 hours preoperatively.
| Dosage form | INJECTABLE |
| Renal impairment | No specific dose adjustment required for renal impairment. Use with caution in severe renal disease; monitor blood pressure closely. |
| Liver impairment | No specific guidelines for hepatic impairment. Use with caution in severe hepatic disease; consider starting at lower end of dosing range. |
| Pediatric use | Intravenous: 0.05-0.1 mg/kg per dose (maximum 5 mg per dose) IV push, repeated every 1-2 hours as needed. For pheochromocytoma surgery: 0.05-0.1 mg/kg IV 1-2 hours preoperatively. |
| Geriatric use | Initiate at lower end of dosing range (2-5 mg IV) due to increased sensitivity to alpha-adrenergic blockade. Monitor blood pressure and heart rate closely; adjust dose based on response. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for REGITINE (REGITINE).
| Breastfeeding | Excreted in breast milk in small amounts. M/P ratio unknown. Caution is advised, monitor infant for potential adverse effects such as hypotension. |
| Teratogenic Risk | FDA Pregnancy Category C. Animal studies have shown teratogenic effects at high doses. There are no adequate and well-controlled studies in pregnant women. The drug should be used during pregnancy only if the potential benefit justifies the potential risk to the fetus. |
| Fetal Monitoring |
■ FDA Black Box Warning
No FDA black box warning.
| Serious Effects |
["Hypersensitivity to phentolamine or any component of the formulation","Myocardial infarction","History of coronary artery disease (relative)","Renal impairment (relative)"]
| Precautions | ["May cause severe hypotension, especially in patients with hypovolemia","Use cautiously in patients with coronary artery disease, cerebrovascular disease, or impaired cardiac function","Risk of tachycardia and cardiac arrhythmias","May aggraviate angina pectoris","Safety in pregnancy not established"] |
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| Monitor maternal blood pressure and heart rate closely. Fetal heart rate monitoring is recommended during labor for potential effects of phentolamine on uterine activity and fetal heart rate. |
| Fertility Effects | No data available regarding effects on fertility in humans. Animal studies have not shown impairment of fertility. |