Triclabendazole

Risk Summary

There are no available data on triclabendazole use in pregnant women to inform a drug-associated risk of major birth defects, miscarriage or adverse maternal or fetal outcomes. Reproductive studies in animals (rat and rabbits) have not shown a risk of increased fetal abnormalities with exposure to triclabendazole during organogenesis at doses approximately 0.3 to 1.6 times the maximum recommended human dose (MRHD) of 20 mg/kg based on body surface area comparison (see Data).

The estimated background risk of major birth defects and miscarriage for the indicated population are unknown. All pregnancies have a background risk of birth defect, loss, or other adverse outcomes. In the U.S. general population, the estimated background risk of major birth defects and miscarriage in clinically recognized pregnancies is 2%-4% and 15%-20%, respectively.

Data

Animal Data

Embryo-fetal developmental toxicity studies revealed no malformations in rats and rabbits at doses up to 200 mg/kg/day and 20 mg/kg/day, respectively (approximately 1.6 times and 0.3 times the MRHD based on body surface area comparison, respectively). The animals were treated orally during organogenesis, starting on Day 6 of the pregnancy until Day 15 in rats and Day 18 in rabbits. Maternal toxicity was noted at doses greater than or equal to 100 mg/kg/day in rats and 10 mg/kg/day in rabbits, which was associated with lower fetus weights and delayed ossification. These findings were considered indicative of delayed physiological growth that was secondary to maternal toxicity. No increase in malformation or other abnormalities was observed at any dose level in either species.

Risk Summary

There are no data on the presence of triclabendazole in human milk, the effects on the breastfed infant, or the effects on milk production. Published animal data indicate that triclabendazole is detected in goat milk when administered as a single dose to one lactating animal. When a drug is present in animal milk, it is likely that the drug will be present in human milk. The developmental and health benefits of breastfeeding should be considered along with the mother’s clinical need for triclabendazole and any potential adverse effects on the breastfed infant from triclabendazole or from the underlying maternal condition.

Mutagenesis

No genotoxic potential was noted for triclabendazole tested in a battery of 6 genotoxicity in vitro and in vivo assays which include a bacterial reverse mutation assay, chromosome aberration assays, and a micronucleus assay.

Impairment of Fertility

No drug-related effects on reproductive performance, mating ratios or fertility indices have been noted in a 2-generation reproductive and developmental toxicity study in rats. The animals were treated with up to 75 ppm triclabendazole via diet, amounting to a mean daily intake of 7.3 mg/kg/day (approximately 0.1 times the MRHD based on body surface area comparison) for a period of 110 days, which included a 12-day mating period beginning on Day 62 of dosing and continuing until the offspring were weaned.

Clinical Trials Experience

Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared to rates in clinical trials of another drug and may not reflect the rates observed in clinical practice.

The safety of triclabendazole was evaluated in 208 adult and pediatric patients 5 years of age and older who participated in 6 clinical trials for the treatment of fascioliasis and received 10 mg/kg or 20 mg/kg of triclabendazole; of these, 6 patients failed the 10 mg/kg dose and were retreated with 20 mg/kg. The 10 mg/kg dosing regimen is not approved. In these trials, 186 patients received a single dose of 10 mg/kg and 28 patients received a dose of 20 mg/kg as two divided doses. Pooled data for adverse reactions reported in more than 2% of the patients in these clinical trials for the 10 mg/kg and 20 mg/kg dosing regimens are presented in Table 1.

Table 1. Adverse Reactions Occurring in >2% of Patients Who Received a Total of 10 mg/kg or 20 mg/kg Triclabendazole for Fascioliasis Treatment (Pooled across 6 studies):

¹ Divided doses were given 6-48 hours apart
² Abdominal pain upper and abdominal pain
³ Jaundice and ocular icterus

Adverse reactions reported in less than or equal to 2% of patients who received a total of 10 mg/kg of triclabendazole were constipation, biliary colic, arthralgia, back pain, spinal pain, and chromaturia. Some adverse reactions associated with triclabendazole treatment in fascioliasis, e.g. abdominal pain, biliary colic, and jaundice, could be secondary to the infection and may be more frequent and/or severe in patients with a heavy worm burden.

The safety profile of triclabendazole 20 mg/kg in divided doses in a non-hepatic parasitic infection (N=104) was generally similar to the safety profile in fascioliasis, except for a lower incidence of post-treatment abdominal pain.

Liver Enzyme Elevations

In clinical studies, up to one third of patients had liver enzyme elevations at baseline, which generally improved post-treatment. Of those with normal liver enzyme values at baseline, 6.8%, 4.5%, 4.2% and 3% of patients had post-treatment elevations in bilirubin, aspartate aminotransferase (AST), alkaline phosphatase (ALP) and alanine aminotransferase (ALT), respectively. Transient increases in liver enzymes and total bilirubin in fascioliasis patients receiving triclabendazole are reported in the literature.

Postmarketing Experience

Resistance to triclabendazole has been reported outside the United States.