Nitroimidazole - albendazole combination therapy, quinacrine use, and risk factors in nitroimidazole-refractory giardiasis: a prospective multicentre observational study
Mørch, Kristine, Chiodini, Peter, Nabarro, Laura, Hannula, Raisa, Neumayr, Andreas, Haanshuus, Christel Gill, Saghaug, Christina, Blomberg, Bjørn, Pettersen, Frank Olav Dahler, Sandnes, Helene Heitmann, Hanevik, Kurt, and Langeland, Nina (2026) Nitroimidazole - albendazole combination therapy, quinacrine use, and risk factors in nitroimidazole-refractory giardiasis: a prospective multicentre observational study. BMC Infectious Diseases, 26. 1598.
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Abstract
Background: Nitroimidazole-refractory giardiasis is an increasing problem. We present data on efficacy of a treatment ladder and on clinical characteristics and assemblage types in nitroimidazole-refractory giardiasis. Methods: We conducted a prospective clinical observational study of adult patients with giardiasis at four centres in Norway and England during 2009 – 2024. Patients with nitroimidazole-refractory giardiasis were treated with albendazole plus a 5-nitroimidazole followed by quinacrine (mepacrine) if failure. Treatment efficacy was defined as negative stool microscopy and/or PCR four to six weeks after treatment. For analyses of assemblage types and risk factors for treatment failure, patients from a previously published Swiss treatment study were additionally included. Assemblage typing of Giardia isolates was performed collectively in the same laboratory by real-time PCR targeting the glutamate dehydrogenase gene (gdh). Predictors identified by univariate analyses were analysed by multivariate logistic regression for association with nitroimidazole failure. Results: A total of 120 patients were prospectively included; 59 of these had nitroimidazole refractory giardiasis and were treated according to the treatment ladder. In addition, 20 patients from the Swiss cohort were included for assemblage and risk factor analyses. A repeated course of nitroimidazole cured only 24% (5/21). Metronidazole or tinidazole in combination with albendazole cured 76% (35/46). Quinacrine was effective in 100% (15/15). Assemblage B was more common in travellers from India and Africa, but only acquisition of infection in India (aOR 11.9; 95%CI 2.94, 47.6) and more recent year of diagnosis (aOR 1.18, 95% CI 1.03, 1.35) were associated with nitroimidazole failure in multivariate analysis. Conclusion: Second line treatment with nitroimidazole in combination with albendazole, and third line treatment with quinacrine, are effective options in nitroimidazole-refractory giardiasis. Nitroimidazole failure seems to be highly associated with infection acquired in India, but not with assemblage A or B. Further studies of resistance mechanisms are needed.
| Item ID: | 94131 |
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| Item Type: | Article (Research - C1) |
| ISSN: | 1471-2334 |
| Keywords: | Albendazole, Assemblage, Giardia, Metronidazole, Ornidazole, Quinacrine, Refractory, Second line, Tinidazole, Treatment |
| Copyright Information: | © The Author(s) 2026. This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/. |
| Date Deposited: | 02 Nov 2026 06:29 |
| FoR Codes: | 32 BIOMEDICAL AND CLINICAL SCIENCES > 3207 Medical microbiology > 320704 Medical parasitology @ 100% |
| SEO Codes: | 20 HEALTH > 2001 Clinical health > 200102 Efficacy of medications @ 50% 20 HEALTH > 2001 Clinical health > 200105 Treatment of human diseases and conditions @ 50% |
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