PRAZEPAM
Clinical safety rating: caution
Comprehensive clinical and safety monograph for PRAZEPAM (PRAZEPAM).
Prazepam is a benzodiazepine that potentiates gamma-aminobutyric acid (GABA) activity at GABA-A receptors, leading to increased chloride ion influx, neuronal hyperpolarization, and central nervous system depression.
| Metabolism | Hepatic metabolism primarily via CYP3A4 to active metabolites including desmethyldiazepam and oxazepam. |
| Excretion | Primarily renal (as conjugated metabolites, mainly oxazepam glucuronide): ~95%; fecal: ~5%. |
| Half-life | Terminal elimination half-life: 36-200 hours (mean ~75 hours). Long half-life leads to accumulation with repeated dosing and prolonged sedation, especially in elderly or hepatic impairment. |
| Protein binding | ~95-98% bound to serum albumin. |
| Volume of Distribution | 0.8-1.5 L/kg. Large Vd indicates extensive tissue distribution, particularly adipose tissue, contributing to slow elimination. |
| Bioavailability | Oral: ~100% (well absorbed); IM: ~80% (erratic absorption, not recommended). |
| Onset of Action | Oral: 30-60 minutes; peak plasma levels at 2-6 hours. |
| Duration of Action | 12-24 hours (single dose); extended with chronic dosing due to long half-life and active metabolites. Clinical effects may persist >24 hours. |
| Molecular Weight | 324.8 |
10-30 mg orally 3-4 times daily; maximum daily dose 60 mg.
| Dosage form | CAPSULE |
| Renal impairment | With CrCl 30-50 mL/min: reduce dose by 25% or extend interval to 12-24 hours. With CrCl <30 mL/min: avoid use or reduce dose by 50% and monitor closely. |
| Liver impairment | Child-Pugh A: no adjustment needed. Child-Pugh B: reduce dose by 50%. Child-Pugh C: avoid use. |
| Pediatric use | Weight-based dosing: 0.2-0.4 mg/kg/day divided every 6-12 hours; maximum 0.6 mg/kg/day. Not recommended for children under 6 months. |
| Geriatric use | Start at lowest effective dose (2.5-5 mg/day) and titrate slowly; maximum 20 mg/day. Avoid in elderly with renal impairment or hepatic dysfunction. |
| 1st trimester | Avoid in first trimester due to increased risk of congenital malformations (cleft palate) from benzodiazepines. |
| 2nd trimester | Use only if benefit outweighs risk; may cause fetal benzodiazepine exposure. |
| 3rd trimester | Avoid near term due to risk of neonatal withdrawal syndrome and floppy infant syndrome (hypotonia, respiratory depression). |
Clinical note
Comprehensive clinical and safety monograph for PRAZEPAM (PRAZEPAM).
| Placental transfer | Crosses placenta; fetal serum concentrations may approach maternal levels due to protein binding differences. |
| Breastfeeding | Prazepam and its active metabolite desmethyldiazepam are excreted into breast milk; long-acting metabolites may accumulate in neonates. Contraindicated during breastfeeding due to potential for sedation and poor feeding. |
■ FDA Black Box Warning
Concomitant use of benzodiazepines and opioids may result in profound sedation, respiratory depression, coma, and death. Reserve concomitant prescribing for patients for whom alternative treatment options are inadequate.
| Serious Effects |
Hypersensitivity to prazepam or other benzodiazepinesSevere hepatic impairmentAcute narrow-angle glaucomaMyasthenia gravisBreastfeeding
| Precautions | Risk of dependence and withdrawal; amnesia; paradoxical reactions; CNS depressant effects; caution in patients with hepatic impairment, respiratory insufficiency, or history of substance abuse. |
| Food/Dietary | Avoid grapefruit and grapefruit juice as they inhibit CYP3A4, potentially increasing prazepam levels and sedation. No other significant food interactions. |
Loading safety data…
| Lactation Rating |
| L5 - Contraindicated |
| Teratogenic Risk | First trimester: Increased risk of oral clefts (odds ratio 1.79). Second and third trimesters: Risk of floppy infant syndrome, neonatal withdrawal, and respiratory depression. Avoid in pregnant women unless absolutely necessary. |
| Fetal Monitoring | Monitor maternal sedation, respiratory rate, and blood pressure. Fetal monitoring for heart rate variability and signs of withdrawal post-delivery. In neonates, monitor for floppy infant syndrome, sedation, and respiratory depression. |
| Fertility Effects | Benzodiazepines may cause menstrual irregularities and ovulatory dysfunction due to CNS depression and hormonal interactions. Effects on male fertility not well studied, but may impair libido and erectile function. |
| Clinical Pearls | Prazepam is a long-acting benzodiazepine with a t1/2 of 30-100 hours; active metabolite desmethyldiazepam extends effect. Not first-line for anxiety due to slow onset; preferred for chronic anxiety with need for consistent levels. Avoid in elderly due to prolonged sedation and fall risk. CYP3A4 substrate; enzyme inducers (e.g., carbamazepine) reduce levels, inhibitors (e.g., ketoconazole) increase toxicity. Withdrawal syndrome can be delayed (days to weeks after discontinuation) due to long half-life. |
| Patient Advice | Take exactly as prescribed; do not increase dose or frequency without consulting your doctor. · Avoid alcohol and other CNS depressants (e.g., opioids, antihistamines) as they increase sedation and respiratory depression risk. · Do not stop abruptly; withdrawal symptoms (e.g., anxiety, insomnia, seizures) can occur. Taper under medical supervision. · May cause drowsiness, dizziness, or impaired coordination. Do not drive or operate machinery until you know how you react. · Inform your doctor if you are pregnant, planning to become pregnant, or breastfeeding. · Store at room temperature, away from moisture and heat. Keep out of reach of children. |