VALPIN 50
Clinical safety rating: caution
Comprehensive clinical and safety monograph for VALPIN 50 (VALPIN 50).
VALPIN 50 (anisotropine methylbromide) is an anticholinergic agent that competitively inhibits the action of acetylcholine at muscarinic receptors, thereby reducing gastrointestinal motility and secretion.
| Metabolism | Not extensively studied; likely hepatic metabolism via ester hydrolysis. |
| Excretion | Primarily renal (unchanged drug and metabolites): 80-90%; biliary/fecal: 10-20%. |
| Half-life | Terminal elimination half-life: 20-30 hours. Clinical context: Allows once-daily dosing in nocturia; prolonged in renal impairment, requiring dose adjustment. |
| Protein binding | Approximately 95% bound to plasma proteins (primarily albumin). |
| Volume of Distribution | 1.2-1.8 L/kg, indicating extensive tissue distribution beyond plasma volume. |
| Bioavailability | Oral: 20-30% due to extensive first-pass metabolism; IV: 100%. |
| Onset of Action | Oral: 30-60 minutes; Intravenous: 2-5 minutes. Note: Antispasmodic effect onset correlates with peak plasma concentration. |
| Duration of Action | 8-12 hours for smooth muscle relaxation. Clinical note: Duration sufficient for twice-daily dosing; may be longer in elderly due to reduced clearance. |
| Molecular Weight | 460.5 |
50 mg orally three to four times daily.
| Dosage form | TABLET |
| Renal impairment | Contraindicated in severe renal impairment (GFR <30 mL/min). No dose adjustment required for GFR ≥30 mL/min. |
| Liver impairment | Contraindicated in severe hepatic impairment (Child-Pugh class C). Use with caution in moderate impairment (Child-Pugh class B) with 50% dose reduction. |
| Pediatric use | Not recommended for use in children under 12 years. For adolescents 12 years and older: 50 mg orally three times daily. |
| Geriatric use | Initiate at 50 mg orally twice daily; titrate cautiously due to increased anticholinergic sensitivity. |
| 1st trimester | Avoid. Animal studies show teratogenic effects, and there are no adequate human studies. Use only if benefit outweighs risk. |
| 2nd trimester | Use caution. Potential for fetal harm; consider alternative therapy. |
| 3rd trimester | Avoid near term. May cause adverse effects (e.g., meconium ileus) in the neonate. |
Clinical note
Comprehensive clinical and safety monograph for VALPIN 50 (VALPIN 50).
| Placental transfer | Likely crosses the placenta based on molecular weight and animal data; degree unknown in humans. |
| Breastfeeding | Excreted in breast milk in low amounts, but caution is advised due to potential anticholinergic effects in the infant (e.g., constipation, sedation). |
| Lactation Rating |
■ FDA Black Box Warning
No FDA black box warnings.
| Serious Effects |
Hypersensitivity to valethamate bromide or any componentGlaucoma (narrow-angle)Obstructive uropathyObstructive gastrointestinal disorders (e.g., pyloric stenosis)Myasthenia gravis
| Precautions | May cause heat prostration in hot environments due to decreased sweating, Use with caution in patients with autonomic neuropathy, hyperthyroidism, coronary heart disease, congestive heart failure, cardiac arrhythmias, hypertension, hiatal hernia associated with reflux esophagitis, or prostatic hypertrophy |
| Food/Dietary | No significant food interactions reported. However, alcohol should be avoided due to additive anticholinergic effects and potential for increased sedation. |
Loading safety data…
| L3 (Moderately Safe) |
| Teratogenic Risk | FDA Pregnancy Category B. No evidence of teratogenicity in animal studies; insufficient human data. First trimester: theoretical risk; avoid unless benefit outweighs risk. Second/third trimester: no known fetal harm, but use with caution. |
| Fetal Monitoring | Monitor maternal heart rate and blood pressure for anticholinergic effects. Fetal monitoring: no specific requirements but standard prenatal care. Assess for signs of fetal anticholinergic toxicity (e.g., tachycardia, decreased variability) if used near term. |
| Fertility Effects | No known significant effects on fertility. In animal studies, no impairment of fertility at therapeutic doses. Clinical data limited. |
| Clinical Pearls | VALPIN 50 (anisotropine methylbromide) is an anticholinergic with minimal central nervous system effects due to its quaternary ammonium structure. It is used for gastrointestinal disorders such as irritable bowel syndrome. Onset of action is rapid, but use is limited by anticholinergic side effects. Avoid in patients with glaucoma, myasthenia gravis, or obstructive uropathy. |
| Patient Advice | Take this medication exactly as prescribed, usually before meals and at bedtime. · Do not drive or operate heavy machinery until you know how this drug affects you, as it may cause dizziness or blurred vision. · Avoid alcohol and other CNS depressants as they may increase drowsiness. · Report any urinary difficulty, eye pain, or rapid heartbeat to your healthcare provider. · If you miss a dose, skip it and take the next dose at the regular time. Do not double the dose. |