TAVIST ALLERGY/SINUS/HEADACHE
Clinical safety rating: caution
Comprehensive clinical and safety monograph for TAVIST ALLERGY/SINUS/HEADACHE (TAVIST ALLERGY/SINUS/HEADACHE).
TAVIST ALLERGY/SINUS/HEADACHE contains clemastine fumarate (first-generation antihistamine) that competitively antagonizes histamine at H1 receptors, and acetaminophen that inhibits cyclooxygenase (COX) enzymes in the CNS, reducing prostaglandin synthesis and fever; phenylpropanolamine is an alpha-adrenergic agonist that causes vasoconstriction of nasal mucosa.
| Metabolism | Clemastine is metabolized via hepatic hydroxylation and demethylation; acetaminophen undergoes hepatic metabolism via conjugation (glucuronidation, sulfation) and CYP2E1-mediated oxidation; phenylpropanolamine is metabolized by hepatic deamination and oxidation. |
| Excretion | Renal excretion of unchanged drug and metabolites accounts for 70-80%, with 15-25% fecal elimination; bilary excretion contributes to remaining |
| Half-life | 5-7 hours for clemastine; 12-15 hours for pseudoephedrine; acetaminophen half-life 2-3 hours. Context: Clemastine half-life supports twice-daily dosing; pseudoephedrine's longer half-life allows 6-8 hour dosing intervals |
| Protein binding | Clemastine: 95-99% bound to plasma proteins; pseudoephedrine: minimal binding (~10-20%); acetaminophen: 10-25% bound |
| Volume of Distribution | Clemastine: 4-6 L/kg (extensive tissue distribution); pseudoephedrine: 2-3 L/kg; acetaminophen: 0.9 L/kg (total body water) |
| Bioavailability | Oral: clemastine ~100%; pseudoephedrine ~100%; acetaminophen 60-90% (FDA range: 63-89%) |
| Onset of Action | Oral: clemastine 30-60 minutes, pseudoephedrine 30 minutes, acetaminophen 15-30 minutes |
| Duration of Action | Clemastine: 12 hours; pseudoephedrine: 4-6 hours (immediate-release); acetaminophen: 4-6 hours. Clinical notes: Combination may require re-dosing based on pseudoephedrine and acetaminophen duration |
1 tablet (acetaminophen 500 mg, diphenhydramine 12.5 mg, phenylephrine 10 mg) orally every 4-6 hours as needed; maximum 4 tablets per day
| Dosage form | TABLET |
| Renal impairment | CrCl 10-50 mL/min: avoid or reduce frequency; CrCl <10 mL/min: contraindicated due to diphenhydramine accumulation and anticholinergic effects |
| Liver impairment | Child-Pugh Class A: no adjustment; Child-Pugh Class B: cautious use (avoid >4 g/day acetaminophen); Child-Pugh Class C: contraindicated due to acetaminophen hepatotoxicity risk |
| Pediatric use | Not recommended for children under 12 years; ages 12-17: same as adult dose |
| Geriatric use | Avoid in patients ≥65 years due to diphenhydramine's anticholinergic effects (increased risk of confusion, falls, urinary retention). Alternative therapies recommended. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for TAVIST ALLERGY/SINUS/HEADACHE (TAVIST ALLERGY/SINUS/HEADACHE).
| Breastfeeding | Clemastine: Excreted in breast milk; reported to cause drowsiness and irritability in infants. M/P ratio unknown. Pseudoephedrine: Excreted in breast milk, M/P ratio approximately 2.6-3.5; may cause irritability and sleep disturbances. Avoid breastfeeding due to potential adverse effects on the infant. |
| Teratogenic Risk | Tavist Allergy/Sinus/Headache contains clemastine (antihistamine) and pseudoephedrine (decongestant). Clemastine: No adequate human studies; animal studies show no teratogenicity at therapeutic doses. Pseudoephedrine: Linked to gastroschisis in first trimester; avoid use. First trimester: Pseudoephedrine contraindicated due to possible vascular disruption. Second/third trimester: Clemastine is generally safe (Category B), but pseudoephedrine may cause fetal tachycardia and reduced uteroplacental blood flow; avoid near term. |
■ FDA Black Box Warning
None.
| Serious Effects |
Hypersensitivity to any component; patients taking MAO inhibitors or within 14 days of stopping; severe hypertension; coronary artery disease; narrow-angle glaucoma; urinary retention; concomitant use of other products containing acetaminophen.
| Precautions | Risk of serious cardiovascular events (hypertension, arrhythmia, stroke) with phenylpropanolamine; avoid use in patients with heart disease, hypertension, thyroid disease, diabetes, or prostatic hypertrophy; may cause drowsiness; avoid alcohol; hepatotoxicity with acetaminophen overdose; do not exceed recommended dose. |
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| Fetal Monitoring | Monitor maternal blood pressure (pseudoephedrine may cause hypertension). Fetal: Ultrasound for growth restriction if used chronically. Assess fetal heart rate (tachycardia). Avoid use during third trimester due to risk of uterine contraction inhibition. |
| Fertility Effects | Clemastine: No known effect on fertility. Pseudoephedrine: Possible reduction in uterine blood flow; no direct evidence of impaired fertility in humans. |