HISTAFED
Clinical safety rating: caution
Comprehensive clinical and safety monograph for HISTAFED (HISTAFED).
HISTAFED is a combination of pseudoephedrine, a sympathomimetic amine that acts as a decongestant by stimulating alpha-adrenergic receptors in the nasal mucosa causing vasoconstriction, and triprolidine, a first-generation antihistamine that competes with histamine for H1-receptor sites on effector cells in the gastrointestinal tract, blood vessels, and respiratory tract, thereby preventing histamine-mediated effects.
| Metabolism | Pseudoephedrine is partially metabolized by hepatic N-demethylation to an inactive metabolite; approximately 55-75% excreted unchanged in urine. Triprolidine undergoes extensive hepatic metabolism via hydroxylation and conjugation, with metabolites excreted in urine. |
| Excretion | Renal (approximately 65% as unchanged drug and metabolites), biliary/fecal (35%) |
| Half-life | 3-4 hours for pseudoephedrine component; shorter in children (2-3 h), prolonged in renal impairment |
| Protein binding | Pseudoephedrine: 20-30% bound to plasma proteins |
| Volume of Distribution | Pseudoephedrine: 2.5-3.5 L/kg, indicating extensive tissue distribution |
| Bioavailability | Oral: 100% (pseudoephedrine is well absorbed) |
| Onset of Action | Oral: 15-30 minutes; intranasal: within 5-10 minutes |
| Duration of Action | Oral: 4-6 hours; extended-release formulations: 12-24 hours; intranasal: 4-6 hours |
60 mg orally every 4 to 6 hours as needed; maximum 360 mg per day.
| Dosage form | SYRUP |
| Renal impairment | GFR 30-59 mL/min: administer every 8-12 hours; GFR 15-29 mL/min: administer every 12-18 hours; GFR <15 mL/min: administer every 24 hours. |
| Liver impairment | Child-Pugh Class A: no adjustment; Child-Pugh Class B: reduce dose by 50%; Child-Pugh Class C: avoid use. |
| Pediatric use | Children 6-11 years: 30 mg orally every 4-6 hours, maximum 180 mg per day; children ≥12 years: same as adult. |
| Geriatric use | Initiate with 30 mg every 6-8 hours; titrate cautiously due to increased risk of anticholinergic effects and dizziness. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for HISTAFED (HISTAFED).
| Breastfeeding | Excreted into breast milk in small amounts; M/P ratio not reported. May cause irritability or drowsiness in nursing infants. Use cautiously; consider alternatives if infant has apnea or seizure disorder. |
| Teratogenic Risk | FDA Pregnancy Category B. Animal studies have not demonstrated fetal risk, but no adequate human studies in pregnant women. First trimester: insufficient data; avoid unless clearly needed. Second and third trimesters: use with caution; possible association with reduced uterine blood flow due to vasoconstriction. Avoid near term due to risk of uterine contractions and potential neonatal respiratory depression. |
■ FDA Black Box Warning
None.
| Common Effects | Nausea Diarrhea Vomiting Skin rash Flu like symptoms Headache Drowsiness Dizziness |
| Serious Effects |
["Hypersensitivity to pseudoephedrine, triprolidine, or any components of the formulation.","Concurrent use with monoamine oxidase inhibitors (MAOIs) or within 14 days of discontinuing an MAOI.","Severe hypertension or coronary artery disease.","Closed-angle glaucoma.","Urinary retention.","Breastfeeding: Avoid use due to potential for adverse effects in infants."]
| Precautions | ["Cardiovascular effects: Use with caution in patients with hypertension, ischemic heart disease, or other cardiovascular conditions due to vasoconstrictor effects.","CNS stimulation: May cause nervousness, dizziness, or insomnia, especially in elderly patients.","Urinary retention: Use caution in patients with prostatic hypertrophy or bladder neck obstruction.","Increased intraocular pressure: Use with caution in patients with narrow-angle glaucoma.","Masking of fever: Antihistamines can mask symptoms of infection."] |
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| Fetal Monitoring | Monitor maternal blood pressure and heart rate; assess for signs of uterine hyperstimulation if used near term. Fetal: non-stress test or biophysical profile if signs of fetal distress or reduced fetal movement. |
| Fertility Effects | No known adverse effects on fertility. Sympathomimetics may theoretically affect ovulation via uterine blood flow changes, but no conclusive human data. |