TPOXX
Clinical safety rating: caution
Comprehensive clinical and safety monograph for TPOXX (TPOXX).
TPOXX (tecovirimat) inhibits the orthopoxvirus VP37 envelope protein, preventing viral egress from infected cells and reducing viral spread.
| Metabolism | Primarily hydrolyzed by esterases to its active metabolite (tecovirimat monocarboxylate); minor CYP3A4 and CYP2C19 involvement. |
| Excretion | Fecal (primarily as unchanged drug, ~75%); renal (~25%, mostly as metabolites; <2% unchanged in urine). |
| Half-life | Terminal half-life ~19 hours (range 10–48 h) in healthy adults; prolonged in renal impairment (up to ~100 h). |
| Protein binding | 80–90% bound to plasma proteins (primarily albumin and α1-acid glycoprotein). |
| Volume of Distribution | Vd ~2.5–3.0 L/kg; indicates extensive tissue distribution and penetration into tissues including skin and lungs. |
| Bioavailability | Oral: ~85–90% under fed conditions; ~60–80% under fasted conditions. |
| Onset of Action | Oral: clinical effect observed within 2–4 days of initiation; IV: immediate upon administration, though clinical response requires time for viral clearance. |
| Duration of Action | Duration of action ~24 hours; recommended dosing every 12 hours for 14 days to maintain therapeutic levels. |
600 mg orally twice daily for 14 days.
| Dosage form | CAPSULE |
| Renal impairment | For GFR 30-89 mL/min: no adjustment. For GFR 15-29 mL/min: 600 mg once daily. For GFR <15 mL/min or dialysis: not recommended. |
| Liver impairment | Child-Pugh A: no adjustment. Child-Pugh B or C: not recommended due to lack of data. |
| Pediatric use | Weight-based: <13 kg: not recommended; 13 to <25 kg: 200 mg twice daily; 25 to <40 kg: 400 mg twice daily; ≥40 kg: 600 mg twice daily. |
| Geriatric use | No specific adjustment required, but monitor renal function due to age-related decline. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for TPOXX (TPOXX).
| Breastfeeding | No data on presence in human milk, effects on breastfed infant, or milk production. M/P ratio is unknown. Due to potential for adverse reactions, consider developmental and health benefits of breastfeeding along with maternal need for TPOXX and potential infant exposure. |
| Teratogenic Risk | Based on animal studies, TPOXX (tecovirimat) is not associated with major malformations in rats or rabbits at exposures up to 8 and 5 times the human exposure (AUC), respectively. Human data in pregnancy are lacking. No fetal risk can be excluded; use only if potential benefit justifies risk. |
■ FDA Black Box Warning
No FDA boxed warning.
| Serious Effects |
None known.
| Precautions | May reduce efficacy of hormonal contraceptives; monitor for hypoglycemia in diabetic patients on insulin/sulfonylureas; avoid use with live smallpox vaccine due to potential interference. |
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| Fetal Monitoring |
| No specific maternal or fetal monitoring requirements beyond routine prenatal care. Consider ultrasound for fetal growth if used in second or third trimester due to lack of human safety data. |
| Fertility Effects | Animal studies in rats showed no effects on fertility or reproductive performance at exposures up to 4.7 times the human AUC. No human data available. |