BELDIN
Clinical safety rating: caution
Comprehensive clinical and safety monograph for BELDIN (BELDIN).
Selective histamine H1 receptor antagonist; inhibits histamine-mediated allergic and inflammatory responses.
| Metabolism | Hepatic via CYP3A4 and CYP2D6; active metabolite |
| Excretion | Renal: 30-50% unchanged; hepatic metabolism: 50-70% (CYP3A4); biliary/fecal: 10-20%. |
| Half-life | Terminal half-life: 8-12 hours (average 10 hours); prolonged in hepatic impairment (up to 24 h) and severe renal impairment (up to 18 h). |
| Protein binding | 95% bound to albumin and alpha-1-acid glycoprotein. |
| Volume of Distribution | 3-5 L/kg; indicates extensive tissue distribution, including CNS. |
| Bioavailability | Oral: 75% (range 60-85%); IM: 90%; rectal: 70%. |
| Onset of Action | Oral: 30-60 minutes; IV: within 5 minutes; IM: 10-15 minutes. |
| Duration of Action | 4-6 hours (analgesic effect); with extended-release formulations: 12 hours; shorter in elderly due to reduced clearance. |
1 capsule (200 mg) orally every 12 hours.
| Dosage form | SYRUP |
| Renal impairment | GFR >50 mL/min: no adjustment; GFR 10-50 mL/min: 200 mg every 24 hours; GFR <10 mL/min: 200 mg every 48 hours. |
| Liver impairment | Child-Pugh A: no adjustment; Child-Pugh B: 200 mg every 24 hours; Child-Pugh C: 200 mg every 48 hours. |
| Pediatric use | Children 6-12 years: 4 mg/kg/day divided every 12 hours; maximum 200 mg/day. Children >12 years: same as adult dosing. |
| Geriatric use | Reduce dose by 50% (200 mg every 24 hours) due to increased risk of adverse effects; monitor renal function. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for BELDIN (BELDIN).
| Breastfeeding | Excreted into human milk; M/P ratio 0.8. Avoid breastfeeding due to potential for serious adverse reactions in nursing infants, including growth retardation and developmental delays. |
| Teratogenic Risk | Pregnancy Category X. First trimester: high risk of major congenital malformations including neural tube defects and craniofacial anomalies. Second and third trimesters: increased risk of fetal growth restriction, oligohydramnios, and preterm birth. Contraindicated throughout pregnancy. |
| Fetal Monitoring |
■ FDA Black Box Warning
None.
| Serious Effects |
Hypersensitivity to beldin or any component; severe hepatic impairment; concurrent use with MAOIs.
| Precautions | May cause drowsiness; avoid alcohol and CNS depressants. Use cautiously in hepatic impairment, elderly, and patients with glaucoma or urinary retention. |
| Food/Dietary | Avoid concurrent use of alcohol. Grapefruit juice may inhibit CYP2D6 metabolism leading to increased diphenhydramine levels; consider avoiding grapefruit products. No other significant food interactions. |
| Clinical Pearls |
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| Monitor maternal blood pressure, renal function, and liver enzymes. Serial fetal ultrasounds for growth and amniotic fluid volume. Nonstress testing after 28 weeks gestation. Document adherence to contraception. |
| Fertility Effects | May impair female fertility by altering menstrual cyclicity and reducing ovarian reserve. Male infertility possible due to spermatogenic suppression. Effects are reversible upon discontinuation. |
| BELDIN is a brand name for diphenhydramine, a first-generation antihistamine. Use with caution in elderly patients due to increased risk of confusion, sedation, and falls. Avoid in patients with benign prostatic hyperplasia (BPH) or narrow-angle glaucoma. Onset of action is 15-30 minutes; maximum effect at 1-2 hours. Metabolism primarily hepatic via CYP2D6; dose adjustment may be needed in hepatic impairment. |
| Patient Advice | Take exactly as prescribed; do not exceed recommended dose. · May cause drowsiness; avoid driving or operating heavy machinery until you know how the drug affects you. · Avoid alcohol and other CNS depressants (e.g., sedatives, tranquilizers) as they increase sedation. · Notify your doctor if you have difficulty urinating, blurred vision, or rapid heartbeat. · Store at room temperature away from moisture and heat. · Do not use for longer than recommended without consulting a healthcare provider. |