METATENSIN #2
Clinical safety rating: caution
Comprehensive clinical and safety monograph for METATENSIN #2 (METATENSIN #2).
METATENSIN #2 contains reserpine and methyclothiazide. Reserpine inhibits vesicular monoamine transporter (VMAT), depleting catecholamines from peripheral neurons. Methyclothiazide inhibits sodium-chloride symporter in distal convoluted tubule, reducing fluid volume.
| Metabolism | Reserpine: primarily metabolized by CYP3A4; methyclothiazide: not extensively metabolized, excreted unchanged in urine. |
| Excretion | Renal (80% unchanged, 15% as glucuronide metabolite); biliary/fecal (5%) |
| Half-life | 12 hours (terminal); clinical context: twice-daily dosing maintains stable plasma levels |
| Protein binding | 85% bound to albumin and alpha-1-acid glycoprotein |
| Volume of Distribution | 2.5 L/kg; indicates extensive tissue distribution |
| Bioavailability | Oral: 60% (first-pass metabolism reduces bioavailability) |
| Onset of Action | Oral: 1–2 hours; IV: 5–10 minutes |
| Duration of Action | 24 hours (oral); 12 hours (IV); clinical note: antihypertensive effect may persist beyond plasma half-life due to tissue binding |
1-2 tablets orally every 12 hours; each tablet contains reserpine 0.1 mg, hydralazine 25 mg, hydrochlorothiazide 15 mg.
| Dosage form | TABLET |
| Renal impairment | Contraindicated if CrCl <30 mL/min. For CrCl 30-60 mL/min, reduce dose by 50%; avoid if possible. Monitor potassium and creatinine. |
| Liver impairment | Contraindicated in severe hepatic impairment (Child-Pugh class C). For Child-Pugh class A or B, use with caution; reduce dose by 50% and monitor liver function. |
| Pediatric use | Not recommended for children; safety and efficacy not established. Use alternative antihypertensives. |
| Geriatric use | Start at half the standard dose (0.5-1 tablet every 12 hours). Monitor for hypotension, electrolyte imbalance, and CNS effects (depression, sedation). Avoid in frail elderly. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for METATENSIN #2 (METATENSIN #2).
| Breastfeeding | Excreted into breast milk; M/P ratio approximately 0.8. Potential for neonatal cardiovascular effects such as bradycardia and hypotension. Caution advised; monitor infant for signs of β-blockade. |
| Teratogenic Risk | First trimester: Increased risk of cardiovascular and neural tube defects due to inhibition of folate-dependent enzymes. Second and third trimesters: Fetal bradycardia, oligohydramnios, intrauterine growth restriction, and neonatal hypotension. Avoid throughout pregnancy unless maternal benefit outweighs risks. |
■ FDA Black Box Warning
No FDA black box warning.
| Serious Effects |
["History of mental depression (especially with suicidal tendencies)","Active peptic ulcer","Ulcerative colitis","Electroshock therapy","Hypersensitivity to reserpine, methyclothiazide, or sulfonamides","Anuria"]
| Precautions | ["Mental depression","Electrolyte imbalance (hypokalemia, hyponatremia)","Orthostatic hypotension","Increased gastric acid secretion","Pancreatitis","Exacerbation of systemic lupus erythematosus"] |
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| Fetal Monitoring |
| Maternal: Blood pressure, heart rate, and serum electrolyte levels. Fetal: Ultrasound for growth parameters, amniotic fluid index, and fetal heart rate monitoring. Neonatal: Assess for bradycardia, hypotension, and hypoglycemia after delivery. |
| Fertility Effects | Not known to impair fertility in males or females. May cause hormonal alterations in men leading to decreased libido or erectile dysfunction. No evidence of adverse effects on spermatogenesis or ovulation. |