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 |
| Molecular Weight | 390.5 |
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 | Data insufficient; avoid unless benefit outweighs risk. No teratogenicity in animal studies. |
| 2nd trimester | Use only if clearly needed; no adequate human studies. |
| 3rd trimester | Avoid near term; may cause premature uterine contractions or hypotension. |
Clinical note
Comprehensive clinical and safety monograph for HISTAFED (HISTAFED).
| Placental transfer | Crosses placenta; extent not quantified |
| Breastfeeding | Excreted in breast milk in low amounts; potential for irritability and poor feeding in infants. Use with caution. |
| Lactation Rating | L2 |
■ FDA Black Box Warning
None.
| Common Effects | Nausea Diarrhea Vomiting Skin rash Flu like symptoms Headache Drowsiness Dizziness |
| Serious Effects |
Hypersensitivity to pseudoephedrine or triprolidineSevere hypertensionSevere coronary artery diseaseMAOI therapy within 14 daysNarrow-angle glaucomaUrinary retention
| 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. |
| Food/Dietary |
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| 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. |
| 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. |
| Avoid high-tyramine foods (e.g., aged cheese, cured meats, fermented products) as pseudoephedrine may potentiate pressor effects. Avoid caffeine as it may increase stimulant effects. Grapefruit juice may increase pseudoephedrine absorption; avoid concurrent use. Take with food to reduce gastrointestinal upset. |
| Clinical Pearls | HISTAFED is a combination of pseudoephedrine and triprolidine. Pseudophedrine can cause hypertensive crisis in patients with severe hypertension or coronary artery disease. Use with caution in patients with hyperthyroidism, diabetes mellitus, ischemic heart disease, increased intraocular pressure, prostatic hyperplasia, or urinary retention. Triprolidine has anticholinergic effects; avoid in patients with narrow-angle glaucoma or bowel obstruction. Onset of decongestant action is 15–30 minutes; duration 4–6 hours. Do not use for more than 7 days. |
| Patient Advice | Do not take with other products containing pseudoephedrine or other decongestants. · Avoid alcohol and sedatives as they may increase drowsiness from triprolidine. · Do not use if you have high blood pressure, heart disease, or an enlarged prostate unless directed by a doctor. · Stop use and consult a doctor if symptoms do not improve within 7 days or are accompanied by fever. · Do not crush or chew extended-release tablets; swallow whole with water. · May cause dizziness or drowsiness; use caution when driving or operating machinery. |