HY-PAM "25"
Clinical safety rating: caution
Comprehensive clinical and safety monograph for HY-PAM "25" (HY-PAM "25").
Hydroxyzine pamoate is a piperazine antihistamine that acts as a histamine H1-receptor antagonist, thereby suppressing histamine-mediated responses in the skin and mucous membranes. Additionally, it exhibits anxiolytic and sedative properties through central nervous system depression via inhibition of subcortical regions.
| Metabolism | Primarily hepatic via CYP3A4 and CYP2D6 isoenzymes; major metabolite is cetirizine. |
| Excretion | Primarily renal (60-70% unchanged drug), with 30-40% biliary/fecal elimination as metabolites. |
| Half-life | Terminal elimination half-life 6-8 hours in healthy adults; prolonged to 12-18 hours in renal impairment (CrCl <30 mL/min) and in elderly patients. |
| Protein binding | 95-98% bound to albumin and alpha-1-acid glycoprotein. |
| Volume of Distribution | 0.2-0.3 L/kg, indicating primarily plasma and extracellular fluid distribution. |
| Bioavailability | Oral: 60-70% (due to first-pass metabolism); Rectal: 80-90%; Intramuscular: 100%. |
| Onset of Action | Intravenous: 30-60 seconds; Oral: 30-60 minutes. |
| Duration of Action | Intravenous: 15-30 minutes (dose-dependent); Oral: 3-6 hours (sustained release forms up to 12 hours). |
25 mg orally once daily, preferably at bedtime, for short-term treatment of insomnia.
| Dosage form | CAPSULE |
| Renal impairment | No dose adjustment required for mild to moderate renal impairment (CrCl ≥30 mL/min). For severe renal impairment (CrCl <30 mL/min), use with caution; no specific dose recommendation available. |
| Liver impairment | For Child-Pugh Class A or B, dose reduction to 12.5 mg daily may be considered due to increased exposure; avoid use in Child-Pugh Class C (severe hepatic impairment). |
| Pediatric use | Not established; contraindicated in pediatric patients due to lack of safety and efficacy data. |
| Geriatric use | Start at 12.5 mg daily; maximum dose 25 mg daily due to increased sensitivity and risk of falls, cognitive impairment, and adverse effects. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for HY-PAM "25" (HY-PAM "25").
| Breastfeeding | Benzodiazepines like HY-PAM 25 are excreted in breast milk. The M/P ratio is approximately 0.5-0.7. With short-acting agents and moderate doses, risk to infant is low but monitor for sedation and poor feeding. Avoid breastfeeding if high maternal doses or chronic use; consider alternative agent. |
| Teratogenic Risk | HY-PAM 25 is a benzodiazepine. First trimester: Data suggest an increased risk of oral clefts (approximately 0.6% vs 0.4% background). Second trimester: Possible risk of other malformations, but data are limited. Third trimester: Chronic use may cause neonatal withdrawal, floppy infant syndrome (hypotonia, lethargy, feeding difficulties), and respiratory depression at delivery. |
■ FDA Black Box Warning
None
| Serious Effects |
["Hypersensitivity to hydroxyzine or any component","Early pregnancy (first trimester) due to potential fetal harm","Porphyria (may precipitate attacks)","Concomitant use with monoamine oxidase inhibitors"]
| Precautions | ["May cause QT prolongation, especially in patients with risk factors","Use with caution in patients with narrow-angle glaucoma, prostatic hypertrophy, or urinary retention","Central nervous system depressant effects may impair mental or physical abilities","Avoid concurrent use with alcohol or other CNS depressants","Use with caution in elderly patients due to increased sensitivity and anticholinergic effects"] |
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| Fetal Monitoring | Monitor maternal sedation, respiratory rate, and blood pressure. Fetal: Ultrasound for growth (if prolonged use), assess for signs of withdrawal or floppy infant syndrome at birth. Neonatal: Apgar scores, respiratory effort, and feeding. Consider therapeutic drug monitoring if toxicity suspected. |
| Fertility Effects | No significant impairment in fertility reported in humans. Animal studies show high doses may affect estrous cycle or spermatogenesis, but clinical relevance is minimal. |