Source: FDA, National Drug Code (US) Revision Year: 2020
Triclabendazole is an anthelmintic against Fasciola species [see Microbiology (12.4)].
Triclabendazole exposure-response relationships and the time course of pharmacodynamics response are unknown.
After oral administration of a single dose of 10 mg/kg triclabendazole with a 560-kcal meal to patients with fascioliasis, mean peak plasma concentrations (Cmax) for triclabendazole, the sulfoxide and sulfone metabolites were 1.16, 38.6, and 2.29 μmol/L, respectively. The area under the curve (AUC) for triclabendazole, the sulfoxide and sulfone metabolites were 5.72, 386, and 30.5 μmol∙h/L, respectively.
Following oral administration of a single dose of triclabendazole at 10 mg/kg with a 560-kcal meal to patients with fascioliasis, the median Tmax for the parent compound and the sulfoxide metabolite was 3 to 4 hours.
Cmax and AUC of triclabendazole and sulfoxide metabolite increased approximately 3-fold and 2-fold respectively when triclabendazole was administered as a single dose at 10 mg/kg with a meal containing a total of approximately 560 kcal (consisting of 2 cups of sweetened white coffee, a roll with cheese, and a roll with butter and jam). In addition, the sulfoxide metabolite Tmax increased from 2 hours in the fasted state to 4 hours in the fed state.
The apparent volume of distribution (Vd) of the sulfoxide metabolite in fed patients is approximately 1 L/kg.
Protein-binding of triclabendazole, sulfoxide metabolite and sulfone metabolite in human plasma was 96.7%, 98.4% and 98.8% respectively.
The plasma elimination half-life (t1/2) of triclabendazole, the sulfoxide and sulfone metabolites in humans is approximately 8, 14, and 11 hours, respectively.
Based on in vitro studies, triclabendazole is primarily metabolized by CYP1A2 (approximately 64%) into its active sulfoxide metabolite and to a lesser extent by CYP2C9, CYP2C19, CYP2D6, CYP3A, and FMO. This sulfoxide metabolite is further metabolized primarily by CYP2C9 to the active sulfone metabolite and to a lesser extent by CYP1A1, CYP1A2, CYP1B1, CYP2C19, CYP2D6 and CYP3A4, in vitro.
No excretion data is available in humans. However, in animals, the drug is largely excreted via the biliary tract in the feces (90%), together with the sulfoxide and sulfone metabolite. Less than 10% of an oral dose is excreted in the urine.
The pharmacokinetics of EGATEN were not studied in patients with renal or hepatic impairment.
No dedicated pediatric pharmacokinetic studies were conducted. However, in one pharmacokinetic study of 20 patients, 7 children (ages 9 to 15 years) were dosed with triclabendazole 10 mg/kg single dose. AUC values of triclabendazole sulfoxide were 20% lower in these pediatric patients in the fed state than in the 13 patients above 15 years of age, but the difference was not statistically significant.
Clinical drug interaction studies have not been conducted for triclabendazole.
Triclabendazole and its sulfoxide and sulfone metabolites have the potential to inhibit CYP1A2, CYP2A6, CYP2B6, CYP2C8, CYP2C9, CYP2C19, CYP2D6, and CYP3A at clinically relevant plasma concentrations, with the highest potential of inhibition on CYP2C19. No in vitro studies were conducted to assess the ability of triclabendazole and its metabolites to induce CYP enzymes. No in vitro studies were conducted to assess the ability of triclabendazole and its metabolites to induce or inhibit transporters.
The mechanism by which triclabendazole exhibits its effect against Fasciola species is not fully elucidated. Studies in vitro and/or in infected animals suggest that triclabendazole and its active metabolites (sulfoxide and sulfone) are absorbed by the tegument of the immature and mature worms, leading to a decrease of the resting membrane potential, inhibition of tubulin function as well as protein and enzyme synthesis. These metabolic disturbances are associated with inhibition of motility, disruption of the surface as well as ultrastructure that includes inhibition of spermatogenesis and vitelline cells.
Triclabendazole and its metabolites are active against the immature and mature worms of Fasciola hepatica and Fasciola gigantica [see Clinical Studies (14)].
Studies in vitro and in vivo as well as case reports suggest a potential for development of resistance to triclabendazole.
The mechanism of resistance may be multifactorial that include changes in drug uptake/efflux mechanisms, the target molecules, and altered drug metabolism. The clinical significance of triclabendazole resistance in humans is not established.
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.
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.
Dietary administration of triclabendazole at a dose of 39 mg/kg/day (1.1-times the MRHD based on body surface area comparison) was associated with a transient increase in the QT and QTc intervals on weeks 5 and 9 in some dogs in a 13-week study resulting in QT (QTc) intervals of 212-227 (318-338) msec in the 39 mg/kg dose group (adjusted) compared to 190-193 (280-297) msec in controls. At Week 13, no statistically significant differences were noted between the treatment and control groups.
Additionally, when dogs were administered triclabendazole at a single dose of 40 or 100 mg/kg (1.1 or 2.7 times the MRHD based on body surface area comparison), increase in QTc intervals was observed resulting in QTc intervals of 217-247 msec compared to a normal (historical control) of 193-231 msec. However, plasma levels of the sulfone metabolite in dogs (which is thought to mediate QTc prolongation) was about 100-500 times the plasma level of the sulfone metabolite measured in human plasma.
In the 13-week study in beagle dogs, slight anemia accompanied by minimal increases in reticulocyte and nucleated red cell counts were observed at 39 mg/kg/day (1.1 times the MRHD based on body surface area comparison) predominantly at week 9 of dosing.
An open label, randomized trial, conducted in Vietnam compared the efficacy of triclabendazole (two 10 mg/kg doses given 12 hours apart with food) to oral artesunate (4 mg/kg, given once daily for 10 days). One hundred patients (age range: 9-74 years) with acute symptomatic fascioliasis were randomized, 50 in each treatment group. At 3 months after treatment, 92% and 76% (difference 16%; 95% CI [1.7, 30.8], p=0.035) of patients in the triclabendazole and artesunate arms respectively, reported no clinical symptoms.
The clinical development program of triclabendazole for the treatment of fascioliasis included 6 non-randomized, open label studies performed in Cuba, Bolivia, Peru, Chile, and Iran in a total of 245 adult and pediatric patients with stool-confirmed fascioliasis. All studies were similar in design. The studied triclabendazole doses ranged from 5 mg/kg to 20 mg/kg administered on Days 1-3. Cure was defined as absence of Fasciola eggs in the stool based on the Kato-Katz method at Day 60 in patients who were positive at baseline. Across these studies, there was a finding of a dose response. Specifically, the Day 60 cure rate was highest (95.5%; 95% CI [77%, 100%]) for the 20 mg/kg dose, which was given in 2 divided doses, followed by cure rates of 88% (95% CI [64%, 99%]), 80% (95% CI [73%, 86%]), and 50% (95% CI [27%, 73%]) in the 15 mg/kg, 10 mg/kg, and 5 mg/kg dose groups, respectively. The 5 mg/kg, 10 mg/kg, and 15 mg/kg dosing regimens are not approved [see Dosage and Administration (2)]. These rates were significantly higher than that estimated from patients receiving an inadequate, non-triclabendazole treatment in a separate study (22%; 95% CI [9.8, 38.2]).
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