TAVIST-1
Clinical safety rating: caution
Comprehensive clinical and safety monograph for TAVIST-1 (TAVIST-1).
TAVIST-1 (clemastine fumarate) is a first-generation antihistamine that acts as a competitive antagonist at histamine H1 receptors, thereby preventing histamine-mediated effects such as vasodilation, increased capillary permeability, and bronchoconstriction. It also exhibits anticholinergic and sedative properties.
| Metabolism | Hepatic metabolism via cytochrome P450 enzymes (CYP3A4) and other unspecified pathways. Undergoes extensive first-pass metabolism. |
| Excretion | Primarily renal: ~60% unchanged; biliary/fecal: ~30% as metabolites; minor via feces. |
| Half-life | Terminal half-life 12–15 hours; clinical dosing interval every 12 hours. |
| Protein binding | ~75% bound to plasma proteins (albumin). |
| Volume of Distribution | ~2.5 L/kg; indicates extensive tissue distribution. |
| Bioavailability | Oral: ~60–70% due to first-pass metabolism. |
| Onset of Action | Oral: 15–30 minutes; peak effect at 1–2 hours. |
| Duration of Action | 8–12 hours for antihistamine effect; may require up to 24 hours for full symptom control. |
1.34 mg orally twice daily; maximum 8.04 mg/day.
| Dosage form | TABLET |
| Renal impairment | CrCl <10 mL/min: not recommended; CrCl 10-30 mL/min: 1.34 mg every 12 hours; CrCl >30 mL/min: no adjustment. |
| Liver impairment | Child-Pugh A: no adjustment; Child-Pugh B: 1.34 mg every 12 hours; Child-Pugh C: not recommended. |
| Pediatric use | Children 6-11 years: 0.67 mg orally every 12 hours; children 12 years and older: adult dosing. |
| Geriatric use | Initiate at 1.34 mg orally once daily; maximum 2.68 mg/day due to increased anticholinergic sensitivity. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for TAVIST-1 (TAVIST-1).
| Breastfeeding | Clemastine is excreted in breast milk in small amounts. The milk-to-plasma (M/P) ratio is approximately 0.5. Because of potential for adverse effects in nursing infants (such as drowsiness, irritability), use caution and consider alternatives, especially in preterm or low-birth-weight infants. |
| Teratogenic Risk | Teratogenic risk profile for TAVIST-1 (clemastine fumarate) is based on limited human data. Animal studies have not shown teratogenic effects. In pregnant women, avoid use during first trimester due to theoretical risks; second and third trimester use is considered safer but only if clearly needed. |
■ FDA Black Box Warning
None
| Serious Effects |
Hypersensitivity to clemastine or any component of the formulation. Avoid in patients with severe liver disease, narrow-angle glaucoma, urinary retention, acute asthma attack, and during breastfeeding. Concomitant use with monoamine oxidase inhibitors (MAOIs) or within 14 days of MAOI therapy.
| Precautions | Sedation and somnolence; avoid alcohol and other CNS depressants. Use with caution in patients with asthma, increased intraocular pressure, hyperthyroidism, cardiovascular disease, hypertension, and prostatic hyperplasia. May impair mental alertness; caution when driving or operating machinery. Use in elderly or debilitated patients may increase risk of dizziness, sedation, and hypotension. Avoid in breastfeeding infants due to risk of anticholinergic effects. |
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| Fetal Monitoring | No specific maternal-fetal monitoring is routinely required for TAVIST-1 use. However, in pregnancy, monitor fetal heart rate patterns and maternal blood pressure if used near term due to potential for maternal hypotension and fetal distress. |
| Fertility Effects | No significant effects on fertility have been reported with TAVIST-1. In animal studies, no impairment of fertility was observed. |