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 |
| Molecular Weight | Chlorpheniramine maleate: 390.87 Da; Pseudoephedrine HCl: 201.70 Da |
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 | Avoid due to potential teratogenic effects; contains chlorpheniramine (antihistamine) and pseudoephedrine (sympathomimetic). First-trimester use of antihistamines has been associated with minor malformations. |
| 2nd trimester | Use with caution; consider fetal risk vs maternal benefit. Pseudoephedrine may cause uterine vasoconstriction. |
| 3rd trimester | Avoid near term; pseudoephedrine may cause uterine contractions or reduce placental perfusion. |
Clinical note
Comprehensive clinical and safety monograph for TAVIST ALLERGY/SINUS/HEADACHE (TAVIST ALLERGY/SINUS/HEADACHE).
| Placental transfer | Both chlorpheniramine and pseudoephedrine cross the placenta. Pseudoephedrine has been detected in cord blood. |
| Breastfeeding | Chlorpheniramine and pseudoephedrine are excreted into breast milk in small amounts. Pseudoephedrine may cause irritability or disturbed sleep in infants. Monitor for adverse effects. Use lowest effective dose for shortest duration. |
■ FDA Black Box Warning
None.
| Serious Effects |
Hypersensitivity to any componentSevere hypertensionCoronary artery diseaseMAOI therapy (current or within 14 days)Narrow-angle glaucomaUrinary retentionSevere hepatic impairment
| 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. |
| Food/Dietary | Avoid alcohol and caffeine-containing beverages. High-tyramine foods (e.g., aged cheese, cured meats) may increase pseudoephedrine pressor effect. |
Loading safety data…
| Lactation Rating | L3 - Moderately Safe |
| 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. |
| 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. |
| Clinical Pearls | Tavist Allergy/Sinus/Headache is a combination of clemastine (first-generation antihistamine), pseudoephedrine (decongestant), and acetaminophen (analgesic). Avoid in patients with hypertension, glaucoma, urinary retention, or MAOI use. Clemastine causes significant sedation; warn about driving. Pseudoephedrine can cause insomnia and tachycardia. Acetaminophen hepatotoxicity risk with >3 g/day or alcohol use. |
| Patient Advice | Do not take more than 6 tablets in 24 hours. · Avoid alcohol and other sedatives due to additive drowsiness. · Do not use if you have high blood pressure, glaucoma, or an enlarged prostate. · Stop and consult a doctor if symptoms persist for more than 7 days. · This product contains acetaminophen; do not combine with other acetaminophen-containing products. |