TRIPROLIDINE HYDROCHLORIDE
Clinical safety rating: safe
CNS depressants may enhance sedative effects May cause marked drowsiness and impair mental and physical abilities.
Competitive antagonist of histamine H1 receptors; inhibits histamine-mediated vasodilation, increased capillary permeability, and bronchoconstriction in allergic reactions.
| Metabolism | Primarily hepatic via cytochrome P450 enzymes (CYP3A4); undergoes N-dealkylation and glucuronidation. |
| Excretion | Renal (primarily as metabolites; ~70% recovered in urine within 24 hours, <5% unchanged). Fecal elimination is minor. |
| Half-life | Terminal elimination half-life approximately 3–4 hours in healthy adults; prolonged in renal impairment (up to 12 hours). |
| Protein binding | ~20% bound to serum albumin; low binding affinity. |
| Volume of Distribution | Approximately 2–5 L/kg (wide distribution, including brain). |
| Bioavailability | Oral: ~40–60% due to first-pass metabolism. |
| Onset of Action | Oral: 30–60 minutes. Intramuscular: 10–20 minutes. Intravenous: immediate (within minutes). |
| Duration of Action | Approximately 4–6 hours after oral administration; shorter with IV/IM due to rapid redistribution. |
| Molecular Weight | 314.85 |
| Action Class | First-generation antihistamine (H1-receptor antagonist) |
2.5 mg orally every 4-6 hours as needed; maximum 10 mg per 24 hours.
| Dosage form | SYRUP |
| Renal impairment | CrCl 30-50 mL/min: reduce dose to 1.25 mg every 6 hours; CrCl <30 mL/min: avoid use or extend interval to every 12 hours. |
| Liver impairment | Child-Pugh Class A: no adjustment; Child-Pugh Class B: reduce dose by 50% or extend interval; Child-Pugh Class C: avoid use. |
| Pediatric use | Children 2-6 years: 1.25 mg orally every 4-6 hours (max 5 mg/day); Children 6-12 years: 2.5 mg orally every 4-6 hours (max 7.5 mg/day); based on weight: 0.1 mg/kg/dose every 6 hours (max 2 mg/kg/day). |
| Geriatric use | Start at 1.25 mg orally every 6 hours; increase cautiously due to increased risk of anticholinergic effects, sedation, and cognitive impairment. |
| 1st trimester | Use only if clearly needed; avoid in first trimester due to potential teratogenic risk (limited human data; anticholinergic effects may cause fetal harm). |
| 2nd trimester | Use with caution; may cause maternal sedation and anticholinergic effects; fetal effects unknown. |
| 3rd trimester | Avoid near term due to risk of neonatal respiratory depression, irritability, or withdrawal symptoms. |
Clinical note
CNS depressants may enhance sedative effects May cause marked drowsiness and impair mental and physical abilities.
| FDA category | Animal |
| Placental transfer | Triprolidine crosses the placenta by passive diffusion; limited data on extent, but placental transfer is likely given its molecular weight and lipophilicity. |
| Breastfeeding |
■ FDA Black Box Warning
None.
| Common Effects | Sedation |
| Serious Effects | Sedation and drowsiness, Anticholinergic effects (dry mouth, urinary retention, blurred vision, constipation), Paradoxical CNS stimulation (especially in children), Hypotension, Tachycardia, Extrapyramidal reactions (rare), Blood dyscrasias (rare) |
Neonates or premature infantsNarrow-angle glaucomaProstatic hypertrophy with urinary retentionSevere hypertension or coronary artery diseaseConcurrent use of MAO inhibitorsKnown hypersensitivity to triprolidine or other antihistamines
| Precautions | May cause drowsiness; avoid driving or operating machinery. Caution in patients with asthma, COPD, increased intraocular pressure, prostatic hyperplasia, urinary retention, or cardiovascular disease. Use with caution in elderly. |
| Food/Dietary |
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| Triprolidine is excreted into breast milk in small amounts. It may cause drowsiness, irritability, or anticholinergic effects in the infant. Manufacturer advises caution; consider alternative antihistamines with lower milk excretion (e.g., loratadine, cetirizine). Monitor infant for sedation and feeding difficulties. |
| Lactation Rating | L3 (Moderately Safe) |
| Teratogenic Risk | Triprolidine hydrochloride is an antihistamine classified as FDA Pregnancy Category C. Animal studies have shown adverse effects (cleft palate, embryonic resorption) at high doses. There are no adequate human studies. First trimester use should be avoided due to potential teratogenic risk. Second and third trimester use is generally considered low risk but may be associated with uterine irritability and neonatal respiratory depression if used near term. |
| Fetal Monitoring | Monitor for maternal sedation, hypotension, and anticholinergic effects. Fetal monitoring is not routinely required but consider ultrasound if first trimester exposure occurred. Monitor neonatal respiratory status if used near delivery. |
| Fertility Effects | In animal studies, high doses of triprolidine have been associated with decreased fertility and implantation failures. Human data are insufficient to determine effect on fertility; potential anticholinergic effects may theoretically affect cervical mucus or implantation. |
| Alcohol and grapefruit juice may increase CNS side effects; avoid concurrent use. No significant food interactions beyond alcohol. |
| Clinical Pearls | Triprolidine is a first-generation antihistamine with significant anticholinergic properties; use cautiously in elderly patients due to increased risk of confusion, urinary retention, and falls. Onset of action is within 15-30 minutes, and duration is 4-6 hours. It is commonly combined with pseudoephedrine for symptomatic relief of upper respiratory allergies. Sedation is pronounced; avoid concurrent use with CNS depressants including alcohol. |
| Patient Advice | Take exactly as directed; do not exceed recommended dose. · May cause marked drowsiness; do not drive or operate heavy machinery until you know how you react. · Avoid alcohol and other sedatives while taking this medication. · May cause dry mouth; sugarless gum or candy may help. · Report difficulty urinating, vision changes, or confusion to your doctor. · Do not use if you have glaucoma, enlarged prostate, or breathing problems unless directed by a healthcare provider. |