Quinacrine Monotherapy Effective as Second-Line Treatment of Nitroimidazole-Refractory Giardiasis

Study authors found quinacrine monotherapy (Q-MT) and albendazole plus chloroquine combination therapy (AC-CT) to be second-line treatment options for nitroimidazole-refractory giardiasis, according to a study published in the journal of Clinical Infectious Diseases.

In this open-label, prospective, multicenter study at 4 different travel clinics in Germany, Belgium, France, and Switzerland, researchers enrolled 106 patients from 2014 to 2020 who failed Giardia duodenalis first-line treatment with nitroimidazole monotherapy, defined as “having persisting or relapsing symptoms together with a stool microscopy positive for G. duodenalis at [least] 2 weeks after completing therapy.”

In the Q-MT arm, 73 patients were given quinacrine 100 mg three times daily for 5 days. In the AC-CT arm, 33 patients were given albendazole 400 mg twice daily plus chloroquine 155 mg twice daily for 5 days.

Investigators evaluated the clinical outcome between 4 and 5 weeks after treatment completion with the following grading: clinical cure, clinical improvement, and clinical failure. They evaluated the parasitological outcome between 2 and 5 weeks after treatment completion with the following grading: parasitological cure and parasitological failure.

It was noted that in the event of a clinical failure and parasitological failure, a cross-over treatment option was offered to the patient.

The clinical outcomes of the Q-MT arm were as follows: 81% (59/73) cure, 19% (14/73) improvement, and 0% failure. The clinical outcomes of the AC-CT arm were as follows: 36% (12/33) cure, 55% (18/33) improvement, and 9% (3/33) failure.

The parasitological outcomes of the Q-MT arm were: 100% (42/42) of clinically cured patients and 100% (14/14) of clinically improved patients had parasitological cure. The parasitological outcomes of the AC-CT arm were as follows: 86% (6/7) clinically cured patients and 33% (6/18) clinically improved patients had parasitological cure, while 14% (1/7) clinically cured patients, 67% (12/18) clinically improved patients, and 100% (3/3) clinically failed patients had parasitological failure.

It was noted that 9 patients from the AC-CT arm were offered the crossover treatment, and 100% of those patients were clinically cured after the Q-MT regimen.

The study authors observed that most patients acquired nitroimidazole-refractory giardiasis in India, which suggests that resistant strains are emerging from that region.

“Our study is the first and largest prospective investigation on the efficacy and tolerability of Q-MT and AC-CT as treatment for nitroimidazole-refractory giardiasis in international travelers. Overall, clinical and parasitological cure was very high in patients treated with Q-MT and rather disappointing in patients who received AC-CT,” the study authors concluded.

Reference

Neumayr A, Schunk M, Theunissen C, et al. Efficacy and tolerability of quinacrine monotherapy and albendazole plus chloroquine combination therapy in nitroimidazole-refractory giardiasis: a TropNet study. Clin Infect Dis. Published online June 11, 2021. doi:10.1093/cid/ciab513