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. |
| Molecular Weight | 474.6 |
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 | Avoid: Potential teratogenicity; limited human data, animal studies show adverse effects. |
| 2nd trimester | Use only if clearly needed: No known risk but insufficient data; consider alternative agents. |
| 3rd trimester | Use only if clearly needed: Risk of premature labor and perinatal complications; avoid near term. |
Clinical note
Comprehensive clinical and safety monograph for TAVIST-1 (TAVIST-1).
| Placental transfer | Crosses placenta; extent and kinetics not well characterized. |
| Breastfeeding | Excreted into breast milk in small amounts; potential for adverse effects in infant such as irritability or drowsiness. Not recommended if safer alternatives exist. |
| Lactation Rating |
■ FDA Black Box Warning
None
| Serious Effects |
Hypersensitivity to clemastine or any componentNarrow-angle glaucomaUrinary retentionSevere hypertensionSevere coronary artery diseaseMAOI 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. |
| Food/Dietary | Avoid alcohol; may enhance sedative effects. No specific food restrictions, but taking with food may reduce GI upset. |
Loading safety data…
| L3 (Moderately Safe) |
| 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. |
| 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. |
| Clinical Pearls | TAVIST-1 (clemastine fumarate) is a first-generation antihistamine with significant anticholinergic properties. It is more sedating than second-generation agents. Onset of action is 30-60 minutes. Use with caution in elderly, glaucoma, urinary retention, and asthma. Avoid in patients with MAOI use within 14 days. May cause CNS depression with alcohol or other CNS depressants. |
| Patient Advice | Take exactly as directed; do not exceed recommended dose. · May cause drowsiness; avoid driving or operating machinery until you know how it affects you. · Do not drink alcohol or use other sedatives while taking this medication. · Notify your doctor if you have glaucoma, difficulty urinating, or prostate problems. · Store at room temperature away from moisture and heat. |