INVERSINE
Clinical safety rating
cautionComprehensive clinical and safety monograph for INVERSINE (INVERSINE).
Mecamylamine is a noncompetitive antagonist of nicotinic acetylcholine receptors, blocking ganglionic transmission in both sympathetic and parasympathetic ganglia.
| Metabolism | Primarily hepatic metabolism (unknown specific enzymes); eliminated renally with unchanged drug and metabolites. |
| Excretion | Primarily renal (about 90% as unchanged drug), with minor biliary/fecal elimination (<10%). |
| Half-life | 3-5 hours in patients with normal renal function; may be prolonged in renal impairment (up to 12-24 hours in severe cases). |
| Protein binding | ~50% bound to plasma proteins (mainly albumin). |
| Volume of Distribution | Approximately 1 L/kg, indicating extensive extravascular distribution. |
| Bioavailability | Oral: 50-75% (due to first-pass metabolism). |
| Onset of Action | Oral: 30-60 minutes; Intravenous: 5-15 minutes. |
| Duration of Action | Oral: 4-6 hours; IV: 2-4 hours. Effect may persist longer in patients with impaired renal function. |
| Molecular Weight | 346.2 |
Initial: 2.5 mg orally twice daily; increase by 2.5-5 mg every 2-3 days until blood pressure controlled; usual maintenance: 10-75 mg/day in 2-4 divided doses; max single dose: 25 mg; max daily dose: 200 mg.
| Dosage form | TABLET |
| Renal impairment | GFR 30-60 mL/min: reduce dose by 50%; GFR 10-29 mL/min: reduce dose by 75%; GFR <10 mL/min: avoid use. |
| Liver impairment | Child-Pugh A: no adjustment; Child-Pugh B: reduce dose by 50%; Child-Pugh C: avoid use. |
| Pediatric use | Not recommended for pediatric use due to lack of safety and efficacy data. |
| Geriatric use | Start at 2.5 mg once daily; increase slowly; monitor for orthostatic hypotension and syncope. |
| 1st trimester | Contraindicated due to teratogenic effects in animal studies and potential for fetal harm. |
| 2nd trimester | Contraindicated; may cause fetal bradycardia and other adverse effects. |
| 3rd trimester | Contraindicated; risk of neonatal bradycardia, hypotension, and respiratory depression. |
Clinical note
Comprehensive clinical and safety monograph for INVERSINE (INVERSINE).
| Placental transfer | Crosses placenta readily based on lipophilicity and animal studies; clinical data demonstrate measurable fetal concentrations. |
| Breastfeeding | Excreted in breast milk in amounts that may cause significant cardiovascular effects in the infant; avoid breastfeeding due to risk of bradycardia, hypotension, and feeding difficulties. |
| Lactation Rating | L5 (Contraindicated) |
| Teratogenic Risk | Category C. First trimester: No adequate human studies; animal studies show embryotoxicity. Second/third trimester: Potential for meconium ileus, neonatal hypotension. Avoid in pregnancy. |
| Fetal Monitoring | Monitor maternal blood pressure and heart rate; fetal growth and amniotic fluid index via ultrasound; neonatal monitoring for hypotension and respiratory depression after delivery. |
| Fertility Effects | May impair fertility in males through reduction of sperm motility; female fertility not adequately studied. |
■ FDA Black Box Warning
None.
| Serious Effects |
PregnancyHypersensitivity to the drugBradycardiaHeart blockShockAcute myocardial infarction
| Precautions | May cause orthostatic hypotension, syncope, and falls. Use with caution in patients with cerebrovascular insufficiency, renal impairment, or recent myocardial infarction. Discontinue if symptoms of paralytic ileus occur. |
| Food/Dietary | Avoid excessive intake of tyramine-rich foods (e.g., aged cheeses, cured meats) as mecamylamine may potentiate pressor effects. Limit alcohol consumption due to additive hypotensive effects. High-sodium foods may counteract antihypertensive effect; follow a low-sodium diet as recommended. |
| Clinical Pearls | INVERSINE (mecamylamine) is a noncompetitive nicotinic acetylcholine receptor antagonist used primarily for its ganglionic blocking effects in severe hypertension. Due to its narrow therapeutic index and significant side effects including orthostatic hypotension, constipation, and urinary retention, it is rarely used today. Monitor for paralytic ileus and bladder distention. Dosage must be titrated carefully based on standing blood pressure. Contraindicated in patients with coronary insufficiency, pyloric stenosis, or recent myocardial infarction. |
| Patient Advice | Take this medication exactly as prescribed; do not change dose without consulting your doctor. · Rise slowly from sitting or lying positions to avoid dizziness from low blood pressure. · Report any constipation, difficulty urinating, or blurred vision to your healthcare provider immediately. · Avoid alcohol and other medications that lower blood pressure without medical advice. · Do not drive or operate heavy machinery if you experience dizziness or blurred vision. · Maintain adequate fluid intake unless otherwise directed by your doctor. |
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