Promethazine exhibits antiparasitic properties in vitro and reduces worm burden, egg production, hepatomegaly, and splenomegaly in a schistosomiasis animal model

Abstract

The treatment and control of schistosomiasis, a neglected disease that affects more than 200 million people worldwide, rely on the use of a single drug, praziquantel. A vaccine has yet to be developed, and since new drug design and development is a lengthy and costly process, drug repurposing is a promising strategy. In this study, the efficacy of promethazine, a first-generation antihistamine, was evaluated against Schistosoma mansoni ex vivo and in a murine model of schistosomiasis. In vitro assays demonstrated that promethazine affected parasite motility and viability, and it induced severe tegumental damage in schistosomes. The 50% lethal concentration (LC50) of the drug was 5.84 μM. Similar to promethazine, schistosomes incubated with atropine, a classical anticholinergic drug, displayed reduced motor activity. In an animal model, promethazine treatment was introduced at an oral dose of 100 mg/kg of body weight for five successive days at different intervals from the time of infection for the evaluation of the stage-specific susceptibility (prepatent and patent infections). Various parasitological criteria indicated the following in vivo antischistosomal effects of promethazine: there were significant reductions in worm burden, egg production, hepatomegaly, and splenomegaly. The highest worm burden reduction was achieved with promethazine in patent infections (>90%). Taken together, considering the importance of the repositioning of drugs in infectious diseases, especially those related to poverty, our data revealed the possibility of promethazine repositioning as an antischistosomal agent.