TAVIST
Clinical safety rating: caution
Comprehensive clinical and safety monograph for TAVIST (TAVIST).
Antihistamine; selective inverse agonist at histamine H1 receptors, blocking histamine-mediated allergic and inflammatory responses.
| Metabolism | Hepatic via CYP450 isoenzymes (primarily CYP3A4); extensive first-pass metabolism. |
| Excretion | Renal excretion of metabolites (approx. 60%) and unchanged drug (<5%); biliary/fecal elimination accounts for about 40%. |
| Half-life | Terminal elimination half-life is 12-15 hours in healthy adults; prolonged in renal/hepatic impairment. |
| Protein binding | Approximately 95% bound to plasma proteins (primarily albumin). |
| Volume of Distribution | Vd is about 2.5-4.0 L/kg, indicating extensive tissue distribution. |
| Bioavailability | Oral bioavailability is approximately 50-60% due to first-pass metabolism. |
| Onset of Action | Oral: 30-60 minutes; peak effect at 2-4 hours. |
| Duration of Action | Duration of antihistamine effect is 4-6 hours for oral administration; may be longer (up to 12 hours) in some individuals. |
1.34 mg orally twice daily; maximum 8.04 mg/day.
| Dosage form | TABLET |
| Renal impairment | CrCl <10 mL/min: contraindicated. CrCl 10-50 mL/min: reduce dose by 50% to 1.34 mg once daily. |
| Liver impairment | Child-Pugh class B or C: reduce dose by 50% to 1.34 mg once daily. Class A: no adjustment. |
| Pediatric use | Not recommended for children under 12 years. For ages 12-17: same as adult dosing. |
| Geriatric use | Initiate at 1.34 mg once daily due to increased anticholinergic sensitivity and risk of confusion, falls. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for TAVIST (TAVIST).
| Breastfeeding | Excreted into breast milk in small amounts. M/P ratio not determined. Use caution, especially in neonates at risk for CNS depression or paradoxical excitation. |
| Teratogenic Risk | Pregnancy Category C. In first trimester, case reports suggest possible association with fetal malformations (cleft palate, inguinal hernia), although animal studies show no teratogenicity at doses up 125 mg/kg/day. Second and third trimesters: No known specific risks; antihistamines may cause uterine contractions near term. |
| Fetal Monitoring |
■ FDA Black Box Warning
None
| Serious Effects |
["Hypersensitivity to active ingredient or any excipients","Use with monoamine oxidase inhibitors (MAOIs)","Narrow-angle glaucoma","Symptomatic prostatic hypertrophy","Bladder neck obstruction","Elderly debilitated patients"]
| Precautions | ["Drowsiness and sedation may impair ability to drive or operate machinery","Avoid concurrent use with CNS depressants (e.g., alcohol, benzodiazepines)","Caution in patients with increased intraocular pressure, hyperthyroidism, cardiovascular disease, or hypertension","Use with caution in elderly patients due to increased sensitivity to anticholinergic effects"] |
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| Monitor maternal blood pressure and heart rate; observe for sedation. Fetal monitoring if used late pregnancy due to potential oxytocin-like effects. Assess neonatal CNS and respiratory status after delivery if used near term. |
| Fertility Effects | No significant impact on fertility reported in animal studies. In humans, antihistamines like clemastine (active ingredient) have not been linked to impaired fertility. |