# The activity of combinations of currently used antigiardial drugs against Giardia duodenalis

## TL;DR

This study examines how combinations of antigiardial drugs affect Giardia duodenalis, finding some combinations are synergistic while others are antagonistic.

## Contribution

The study provides the first in vitro evaluation of drug combinations against Giardia duodenalis.

## Key findings

- Metronidazole with albendazole or quinacrine showed additive effects.
- Metronidazole with nitazoxanide showed synergistic effects.
- Albendazole with nitazoxanide showed antagonistic effects.

## Abstract

Drug-combination therapies are needed to combat treatment refractory giardiasis. However, data describing the activity of combinations of currently used drugs against Giardia duodenalis are unavailable.

The in vitro activity of combinations of currently used antigiardial drugs were investigated against G. duodenalis.

Combinations of metronidazole with albendazole or quinacrine, and quinacrine with nitazoxanide, behaved additively, whereas combinations of metronidazole with nitazoxanide, albendazole or quinacrine behaved synergistically. Combinations of albendazole with nitazoxanide behaved antagonistically.

While combinations of metronidazole with nitazoxanide, or albendazole with quinacrine, may be effective treatments of giardiasis, combinations of albendazole with nitazoxanide are likely to result in negative pharmacodynamic interactions.