In vitro and in vivo assessment of the benzydamine-mediated interference with the hepatic S-oxidation of the anthelmintic albendazole in sheep

Pharmacological characterization of geraniol in sheep and its potential use in the control of gastrointestinal nematodes

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Geraniol is a monoterpene which showed in vitro antiparasitic effect.

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The oxidative metabolism of albendazole is reduced by geraniol in vitro.

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There were not in vivo pharmacokinetic interactions after the coadministration of albendazole and geraniol to sheep.

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The residence time of geraniol after its oral administration to sheep is very short.

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The efficacy of geraniol against Haemonchus contortus was below the threshold established.

Geraniol (GNL) was effective against gastrointestinal nematodes in vitro; nevertheless, the anthelmintic effect of phytochemicals combined with synthetic drugs has been little explored in vivo. This article characterized in vitro / in vivo the pharmacological features of GNL in sheep as well as its pharmacokinetic interaction with albendazole (ABZ). Additionally, the in vivo efficacy of GNL against Haemonchus contortus was evaluated in lambs. Liver microsomes from lambs were incubated in the absence or presence of GNL to analyze CYP1A1, CYP1A2 and FMO metabolic pathways. The effect of GNL on the hepatic sulfoxidation and sulfonation of ABZ and the ruminal sulforeduction of albendazole sulfoxide (ABZSO) was assessed. The in vivo pharmacokinetic interaction of ABZ and GNL was evaluated in lambs. The effect of GNL on the fecal egg count was evaluated in lambs infected with a resistant isolate of H. contortus. In sheep liver microsomes, the presence of 2 mM GNL reduced the CYP1A1, CYP1A2 and FMO pathways by 77.9, 90.8 and 84.5%, respectively, with respect to control (P < 0.05). In the presence of 2 mM GNL, the ABZ sulfoxidation decreased from 114.4 ± 8.49 (control) to 50.24 ± 11.1 nmol/min.mg, and ABZSO₂ production decrease from 0.52 ± 0.14 to 0.09 ± 0.03 nmol/h.mg. No changes in the pharmacokinetic behavior of ABZ were observed in the presence of GNL. The in vivo efficacy of four doses of GNL was 40.5%. These findings highlight the importance of integrated in vitro / in vivo pharmaco-parasitological studies to develop new pharmacological tools for controlling gastrointestinal parasites.

Combination of bioactive phytochemicals and synthetic anthelmintics: In vivo and in vitro assessment of the albendazole-thymol association

The search of novel strategies for anthelmintic control is a crucial need considering the widespread increase in resistant parasitic populations in livestock. Bioactive phytochemicals may contribute to improve parasite control by enhancing the effect of existing anthelmintic drugs. The aim of the current work was to evaluate the in vivo and in vitro pharmaco-chemical interaction and the in vivo efficacy of the combination of albendazole (ABZ) with thymol (TML) in lambs naturally infected with resistant gastrointestinal nematodes. Thirty (30) lambs were allocated into three experimental groups. Each group was treated orally with either ABZ (5 mg/kg), TML (150 mg/kg, twice every 24 h) or the co-administration of both compounds. Blood samples were collected between 0 and 51 h post-treatment and TML, ABZ and its metabolites were measured by HPLC. Individual faecal samples were collected at days -1 and 14 post-treatment to perform the faecal egg count reduction test. Additionally, the effect of TML on the sulphoreduction and sulphonation of ABZ sulphoxide was assessed in vitro using ruminal content and liver microsomes, respectively. The metabolism of TML in the ruminal content was very low and the monoterpene exhibited a low degree of association with the particulate phase of the ruminal content. No changes in the pharmacokinetic behavior of ABZ sulphoxide were observed in the presence of the natural product (TML). In contrast, the ABZ sulphone Cmax and AUC were lower (P 0.002 and 0.001 respectively) in the co-administered animals (0.16 ± 0.07 μg/mL and 3.63 ± 1.21 μg.h/mL) compared with those that received ABZ alone (0.45 ± 0.15 μg/mL and 9.50 ± 2.84 μg.h/mL). TML was detected in the bloodstream between 1 and 48 h post-treatment, which indicates the time of target nematodes being exposed to the bioactive monoterpene. However, the in vivo efficacy of TML was 0% and the presence of this terpene did not increase the efficacy of ABZ. The presence of TML significantly inhibited the ruminal sulphoreduction (P 0.001) and the hepatic sulphonation (P 0.001) of ABZ sulphoxide. These observations point out that in vivo pharmaco-parasitological studies are relevant to corroborate the adverse kinetic/metabolic interactions and the efficacy of bioactive natural products combined with synthetic anthelmintics.

In vitro inhibition of the hepatic S-oxygenation of the anthelmintic albendazole by the natural monoterpene thymol in sheep

Combinations of bioactive phytochemicals with synthetic compounds have been suggested as promissory tools for the improvement of nematode control in livestock. Bioactive phytochemicals may interfere with the activity of drug-metabolizing enzymes and delay the metabolic conversion of anthelmintics into less potent metabolites.This research assessed the effect of the monoterpene thymol (TML) on the in vitro hepatic metabolism of the anthelmintic albendazole (ABZ) in sheep.Liver microsomes from four (4) Texel lambs were incubated with ABZ (50 µM) in absence or in presence of TML (0.05-10 mM).The concentration of TML producing a 50% decrease in ABZ S-oxygenation (IC50) was 13.5 mM. The FMO-dependent S-oxygenation of ABZ was markedly inhibited by the monoterpene (54.1 ± 11.6%, p < .01). In agreement with this observation, TML produced a marked inhibition of benzydamine (BZ) N-oxidase, a specific FMO activity.The CYP-dependent production of the sulfoxide metabolite (ABZSO) was less affected, being 25.3 ± 17.5 lower (p < .05) in presence of TML. Additionally, TML completely abolished the specific CYP1A1-dependent enzyme activity 7-ethoxyresorufin O-deethylase.Overall, the results presented here show that, in addition to its own anthelmintic affect, TML may potentiate ABZ anthelmintic activity by preventing its metabolic conversion into a less active metabolite.