A randomized trial comparing mebendazole and secnidazole for the treatment of giardiasis

Giardiasis treatment: an update with a focus on refractory disease

PURPOSE OF REVIEW

Giardiasis remains a common cause of diarrhea and intestinal enteropathy globally. Here we give an overview of clinical treatment studies and discuss potential mechanisms and molecular targets for in-vitro testing of drug resistance.

RECENT FINDINGS

Giardia is a cause of disease both in diarrheal and nondiarrheal cases. The prevalence of treatment refractory giardiasis is increasing. Recent studies reveal 5-nitroimidazole refractory infection occurs in up to 50% of cases. Mechanisms of drug resistance are not known. Placebo controlled studies of drug efficacy, taking the self-limiting course of giardiasis into account, has not been reported. No randomized controlled trials of treatment of refractory infection have been performed the last 25 years. Based on the clinical studies reported, combination treatment with a 5-nitroimidazole and a benzimidazole is more effective than repeated courses of 5-nitroimidazole or monotherapies in refractory cases. Quinacrine is effective in refractory cases, but potentially severe side effects limit its use.

SUMMARY

A combination of a 5-nitroimidazole and albendazole or mebendazole, and quinacrine monotherapy, are rational choices in nitroimidazole refractory infections, but randomized controlled studies are needed. Further research into more recent clinical isolates is necessary to uncover mechanisms for the increase in metronidazole refractory giardiasis observed during the last decade.

A systematic review of the literature on mechanisms of 5-nitroimidazole resistance in Trichomonas vaginalis

BACKGROUND

Trichomonas vaginalis is the most common non-viral sexually transmitted infection. 5-Nitroimidazoles [metronidazole (MTZ) and tinidazole (TDZ)] are FDA-approved treatments. To better understand treatment failure, we conducted a systematic review on mechanisms of 5-nitroimidazole resistance.

METHODS

PubMed, ScienceDirect and EMBASE databases were searched using keywords Trichomonas vaginalis, trichomoniasis, 5-nitroimidazole, metronidazole, tinidazole and drug resistance. Non-English language articles and articles on other treatments were excluded.

RESULTS

The search yielded 606 articles, of which 550 were excluded, leaving 58 articles. Trichomonas vaginalis resistance varies and is higher with MTZ (2.2-9.6%) than TDZ (0-2%). Resistance can be aerobic or anaerobic and is relative rather than absolute. Differential expression of enzymes involved in trichomonad energy production and antioxidant defenses affects 5-nitroimidazole drug activation; reduced expression of pyruvate:ferredoxin oxidoreductase, ferredoxin, nitroreductase, hydrogenase, thioredoxin reductase and flavin reductase are implicated in drug resistance. Trichomonas vaginalis infection with Mycoplasma hominis or T. vaginalis virus has also been associated with resistance. Trichomonas vaginalis has two genotypes, with greater resistance seen in type 2 (vs type 1) populations.

DISCUSSION

5-Nitroimidazole resistance results from differential expression of enzymes involved in energy production or antioxidant defenses, along with genetic mutations in the T. vaginalis genome. Alternative treatments outside of the 5-nitroimidazole class are needed.

Infections with Giardia duodenalis and Entamoeba histolytica/Entamoeba dispar as Hidden and Prevalent Conditions in Periurban Communities in the State of Rio de Janeiro, Brazil

This study aims to assess the prevalence, distribution, and etiological profile of intestinal parasitism in children living in periurban areas in Cachoeiras de Macacu, Rio de Janeiro, Brazil. A community-based cross-sectional survey (n = 479) was carried out. Prevalence of infection with G. duodenalis and E. histolytica/E. dispar was 8.6% (n = 41) and 13.4% (n = 64), respectively. Infection with G. duodenalis was significantly more frequent among children living in poor families (24/187 (12.8%) vs. 16/272 (5.9%); prevalence ratio (PR) = 2.18; 95% confidence interval (CI) = 1.19–3.99; p=0.011). This difference was also significant for infection with any pathogenic parasite (43/187 (23%) vs. 40/272 (14/7%); PR = 1.56; 95% CI = 1.06–2.30; p=0.026). In addition, people residing in houses with more than four inhabitants showed significantly higher positivity for infections with G. duodenalis and with E. histolytica/E. dispar (22/138 (15.9%) vs. 16/311 (5.1%); PR = 3.09; 95% CI = 1.68–5.71; p < 0.001 for G. duodenalis and 32/138 (23.2%) vs. 30/311 (9.6%); PR = 2.40; 95% CI = 1.52–3.79; p < 0.001 for E. histolytica/E. dispar). Laboratory diagnosis of protozoan enteric infections and effective drugs for their treatment are unmet goals in the primary health care system. Therefore, giardiasis and amebiasis are neglected conditions.

5-Nitroimidazole refractory giardiasis is common in Matanzas, Cuba and effectively treated by secnidazole plus high-dose mebendazole or quinacrine: a prospective observational cohort study

OBJECTIVE

To evaluate the effectiveness and tolerability of secnidazole combined with high-dose mebendazole for treatment of 5-nitroimidazole-resistant giardiasis.

METHOD

Adults with microscopically verified Giardia intestinalis monoinfection attending a secondary level hospital in Matanzas City, Cuba were prospectively included in a cohort. A recently introduced treatment ladder consisting of metronidazole as first-line treatment, followed by secnidazole, tinidazole, secnidazole plus mebendazole and quinacrine as second-to fifth-line treatments, respectively, was used. Adverse events and treatment success were determined by questioning and microscopy on concentrated stool samples, respectively on days 3, 5 and 7 after the end of treatment. If G. intestinalis was detected on day 3, 5 or 7, then the infection was classified as refractory and no further microscopy was performed.

RESULTS

A total of 456 individuals were included. Metronidazole, 500 mg three times daily for 5 days, cured 248/456 (54%) patients. A single 2-g secnidazole dose as second-line treatment cured 50/208 (24%) patients. A single 2-g tinidazole dose as third-line treatment cured 43/158 (27%) patients. Three rounds of 5-nitroimidazole therapy therefore cured 341/456 (75%) patients. Secnidazole plus mebendazole (200 mg every 8 hours for 3 days) cured 100/115 (87%) of nitroimidazole refractory infections. Quinacrine cured the remaining 15 patients. All treatments were well tolerated.

CONCLUSIONS

5-Nitroimidazole refractory giardiasis was common, indicating that an alternative first-line treatment may be needed. Retreatment of metronidazole refractory giardiasis with an alternative 5-nitroimidazole was suboptimal, indicating cross-resistance. Mebendazole plus secnidazole were well tolerated and effective for the treatment of 5-nitroimidazole refractory G. intestinalis infection in this setting.

Efficacy of mebendazole in paediatric patients with giardiasis: A systematic review and meta-analysis

Mebendazole (MBZ), a benzimidazole compound, has received attention in treating patients with giardiasis because it has shown beneficial effects both in vitro and in vivo. The aim of this study was to assess with a systematic review and meta-analysis of randomized controlled trials (RCTs) the efficacy of MBZ compared to other antigiardial agents in children. We searched RCTs of MBZ for the treatment of Giardia infections published in PubMed and EBSCOhost. Application of inclusion and exclusion criteria, data extraction, and assessment of methodological quality were independently performed in duplicate. The primary outcome was the parasitological cure. We included 7 RCTs in the systematic review (639 patients). There was no clinical difference in the parasitological cure between MBZ and metronidazole (MTZ). The relative risk (RR) was 0.81 [95% Confidence Interval 0.61-1.09], with high heterogeneity (4 trials, I² = 81%). The prediction interval expected to cover the results of a new trial was wide enough (0.22-2.96) to support both a clinically relevant difference favouring either MBZ or MTZ. The decision to support any treatment should be based not only on efficacy but also safety and cost. Although our results suggest that MBZ may be an effective treatment option for children with Giardia infection, they should also be interpreted and translated into clinical practice with caution, as the evidence is based on a limited number of RCTs presenting high heterogeneity.

Effectiveness and Tolerability of 3-Day Mebendazole Treatment of Giardia duodenalis Infection in Adults and Children: Two Prospective, Open-Label Phase IV Trials

BACKGROUND

Giardia duodenalis is the most common intestinal pathogenic protozoan infection reported in humans. Both in vitro studies and 4 separate, sequential, comparative clinical trials conducted by our group in Cuba demonstrated mebendazole activity against G. duodenalis infection in both children and adults.

OBJECTIVE

The 2 additional, prospective, open-label, Phase IV follow-up studies reported here were performed to further assess the effectiveness and safety profile of mebendazole in the outpatient treatment of G. duodenalis infection.

METHODS

Assenting children (n = 522) whose guardians gave permission and consenting adults (n = 423) diagnosed with G. duodenalis infection were given mebendazole (200 mg 3 times daily for 3 days). Medical histories and stool samples were obtained and physical/laboratory examinations were performed pretreatment then repeated on days 3, 5, and 7 after treatment completion. The evaluation of efficacy (ie, cure) was based on parasitologic response to therapy. Participants were considered cured, if no Giardia trophozoites or cysts were found in any of the 3 posttreatment fecal specimens evaluated by direct wet mounts and/or after Ritchie concentration techniques.

RESULTS

No participant refused to be enrolled and all returned for follow-up examinations. At the end of the treatment, stool samples were negative in 450 out of 522 children (86.2%) and 392 of 423 adults (92.7%). Treatment was well tolerated. In adults, the only adverse effect reported was abdominal pain (6.2%). Side effects reported in children included abdominal pain (5.6%), nausea (2.9%), and vomiting (2.3%). Reported side effects were all mild, transient, and self-limited and did not require discontinuation of treatment or additional medication.

CONCLUSIONS

Mebendazole may be an effective alternative treatment of G. duodenalis infections in both children and adults.

Secnidazole: next-generation antimicrobial agent for bacterial vaginosis treatment

Secnidazole is a next-generation 5-nitroimidazole approved for more than three decades in Europe, Asia, South America and Africa and recently in the USA as a single-dose (2 g) treatment of bacterial vaginosis (BV). Secnidazole is characterized by potent in vitro antimicrobial activity against BV-associated pathogens, as well as prolonged terminal elimination half-life and systemic exposure. These characteristics form the basis of effective and safe treatment of BV with a 2-g single-dose secnidazole regimen, which was recently confirmed in double-blind, placebo-controlled clinical trials conducted in the USA. The option to treat BV with single-dose secnidazole not only cures the primary infection but also may diminish risks of serious sequelae of untreated or undertreated infection.

In Vitro Study of the Susceptibility of Clinical Isolates of Trichomonas vaginalis to Metronidazole and Secnidazole

Nitroimidazoles (metronidazole [MTZ] and tinidazole [TNZ]) are the only drugs recommended for treatment of Trichomonas vaginalis infections. MTZ resistance occurs in 4% to 10% of cases of vaginal trichomoniasis (R. D. Kirkcaldy et al., Emerg Infect Dis 18:939-943, 2012; J. R. Schwebke and F. J. Barrientes, Antimicrob Agents Chemother 50:4209-4210, 2006) and TNZ resistance in 1% of cases (J. R. Schwebke and F. J. Barrientes, Antimicrob Agents Chemother 50:4209-4210, 2006). Emerging nitroimidazole-resistant trichomoniasis is concerning, because few alternatives to standard therapy exist. We assessed the prevalence of in vitro aerobic MTZ and secnidazole resistance among T. vaginalis isolates collected in 2015 to 2016 from 100 women in Birmingham, Alabama, with positive cultures. Archived specimens were treated with secnidazole or MTZ (0.2 to 400 μg/ml) for 48 h, according to U.S. Centers for Disease Control and Prevention protocols. Ninety-six (96%) of the 100 clinical Trichomonas isolates tested demonstrated lower minimum lethal concentrations for secnidazole than for MTZ, suggesting that secnidazole has better in vitro activity than MTZ.

Efficacy of 5-nitroimidazoles for the treatment of giardiasis: a systematic review of randomized controlled trials

Background

Giardiasis is one of the most common causes of diarrheal disease worldwide and 5-nitroimidazoles (5-NI) are the most commonly prescribed drugs for the treatment of giardiasis. We evaluated the efficacy of 5-nitroimidazoles (5-NI) in the treatment of giardiasis in a systematic review of randomized controlled trials (RCTs).

Methodology/Principal Findings

We conducted a comprehensive literature search in PubMed-Medline, Scopus, Web of Science and Cochrane Library for RCTs evaluating the efficacy of 5-NI vs. control (placebo or active treatment) on parasitological cure in patients with parasitologically-demonstrated giardiasis. The search was performed in May 2013 with no language restriction by two authors independently. The efficacy outcome was parasitological cure, and harmful outcomes were abdominal pain, bitter or metallic taste, and headache. We included 30 RCTs (n = 3,930). There was a significant and slightly higher response rate with 5-NI in giardiasis treatment (RR 1.06, 95%CI 1.02–1.11, p = 0.005). There was high heterogeneity among studies (I² = 72%). The response rates for metronidazole, tinidazole and secnidazole were similar (RR 1.05, 95%CI 1.01–1.09, p = 0.01; RR 1.32 95%CI 1.10–1.59, p = 0.003; and RR 1.18 95%CI 0.93–1.449, p = 0.18, respectively). On subgroup analyses, the response rates did not vary substantially and high heterogeneity persisted (I² = 57%–80%). Harmful outcomes were uncommon, and 5-NIs were associated with lower risk of abdominal pain, and higher risk of both bitter or metallic taste and headache.

Conclusions

Studies investigating the efficacy of 5-NI in giardiasis treatment are highly heterogeneous. 5-NIs have a slightly better efficacy and worse profile for mild harmful outcomes in the treatment of giardiasis in comparison to controls. Larger high quality RCTs are needed to further assess efficacy and safety profiles of 5-NI.

Giardiasis is a major diarrheal disease with worldwide distribution. 5-nitroimidazoles, which include metronidazole and tinidazole, are the most commonly used drugs in the treatment of giardiasis. In recent years, many other drugs with variable efficacies and adverse effects have been proposed for the treatment of giardiasis. No systematic review has evaluated efficacy of 5-nitroimidazoles as a group in comparison to the other antigiardial drugs. In this context, we performed a systematic review of the literature to identify randomized controlled trials comparing the efficacies of 5-nitroimidazoles with a control drug with the aim of assessing effectiveness of 5-nitroimidazoles in the treatment of giardiasis. Four research databases were searched; 30 trials with 3,930 subjects met our inclusion criteria. Results show that there was a high variation of study outcomes between included studies. 5-nitroimidazoles were associated with higher giardiasis cure rates than controls; also, 5-nitroimidazoles are associated with lower risk of abdominal pain, and higher risks of bitter or metallic taste and headache than controls.

Giardia intestinalis: effects of Pulsatilla chinensis extracts on trophozoites

Pulsatilla chinensis is a medicinal root plant that has been used to treat a wide range of disease conditions. Our study determined the antiprotozoal activity of various P. chinensis extracts and fractions against Giardia intestinalis including their effects on parasite growth, cell viability, adherence, and morphology. Ethyl acetate extracts (IC50 = 257.081 μg/ml) were the most active to inhibit the growth of G. intestinalis followed by aqueous extract (PWE), saponins, and n-butanol extract. The PWE and ethyl acetate extract inhibited G. intestinalis trophozoites adherence after 3 h of incubation and killed almost 50 % of the parasite population in a time-dependent manner. Changes in morphology, presence of precipitates in the cytoplasm, dissolved cytoplasm with large vacuole, break of flagella and ventral disk, membrane blebs, and intracellular and nuclear clearance of the treated trophozoites were observed by scanning and transmission electron microscopy. We demonstrated that P. chinensis induced these changes in G. intestinalis morphology and consequently has potential therapeutic use against giardiasis.

Albendazole versus metronidazole in the treatment of adult giardiasis: a randomized, double-blind, clinical trial

BACKGROUND

Albendazole (ABZ) is a benzimidazole carbamate compound currently in use for human medical practice against enterobiasis and soil-transmitted helminthiasis (STH); However, its spectrum of activity is broad and goes beyond these infections.

OBJECTIVE

This study compares the efficacy and safety of ABZ versus metronidazole (MTZ) in human giardiasis.

RESEARCH DESIGN AND METHODS

A randomized, double-blind, clinical trial was carried out at the Centre of Hygiene, Epidemiology and Microbiology in Matanzas City, Cuba. Adult patients with confirmed symptomatic G. duodenalis mono-infection were randomly assigned to receive either ABZ [400 mg daily (n = 75)] or MTZ [250 mg t.i.d. (n = 75)], both for 5 days. Follow-up fecal samples were obtained at 3, 5, 7 days after treatment end.

RESULTS

The efficacy was similar for both treatment groups: ABZ (82.6%) and MTZ (85.3%); p > 0.05. Side-effects including bitter taste, headache, vomiting and dizziness were significantly higher in the MTZ group. Abdominal pain was significantly higher in ABZ group.

CONCLUSION

ABZ was found as effective as MTZ in the treatment of G. duodenalis infections in adult patients from Cuba and could be a useful drug in areas where co-infection with STH infections is common.

Mebendazole compared with secnidazole in the treatment of adult giardiasis: a randomised, no-inferiority, open clinical trial

To compare the efficacy and safety of mebendazole and secnidazole in the treatment of giardiasis in adult patients, a single-centre, parallel group, open-label, randomized non-inferiority trial was carried out. One-hundred and 26 participants who had symptomatic Giardia mono-infection took part in the study. Direct wet mount and/or Ritchie concentration techniques and physical examinations were conducted at the time of enrolment and at the follow-up visit. The primary outcome measure was parasitological cure, performed at 3, 5, 10 days post-treatment. Negative faecal specimens for Giardia were ensured by the same parasitological techniques. At follow up (day 10) the parasitological cure rate for the per protocol populations was 88.7% (55/62) for MBZ and 91.8% (56/61) for SNZ. For the intention to treat populations the cure rate at the end of treatment was 85.9% (55/64) for MBZ and 90.3% (56/62) for SNZ. Both analyzes showed there was not significant statistical difference between MBZ and SNZ treatment efficacy. Both drugs were well tolerated, only mild, transient and self-limited side effects were reported and did not require discontinuation of treatment. A 3-day course of mebendazole seems to be as efficacious and safe for treatment of giardiasis as a single dose of secnidazole in adults.

The effects of dihydroartemisinin on Giardia lamblia morphology and cell cycle in vitro

Several anti-Giardia drugs, such as metronidazole, tinidazole, mebendazole, albendazole and furazolidone, are usually effective but have severe side effects and potential toxicity. An urgent need exists for more effective and less toxic agents that can act against this protozoan. For this purpose, the effects of dihydroartemisinin (DHA) on Giardia lamblia were investigated in vitro. Axenically grown G. lamblia trophozoites were treated with DHA (LD(50) = 200 microg/mL) at different time intervals. The morphological and ultrastructural changes of the treated trophozoites were observed by both light and transmission electron microscopy (TEM). Changes in the cell cycle of the treated cells were observed by flow cytometry. By light microscopy, we observed that DHA-treated trophozoites were detached from the wall of the culture tube and shown bradypraxia and bubbles in the dorsal and ventral surfaces. Ultrastructural observations by TEM revealed that DHA promoted modifications of the cell shape, pronounced dorsal vesiculation, plasma membrane blebbing, disaggregation of ribosomes, depletion of cytoplasmic matrix and heavy deposition of electron-dense precipitates on the cytoplasm and nucleus. The main changes observed in the treated group included the following: (1) trophozoites were rounder in shape and the endoplasmic reticulum was dilated, (2) enlarged trophozoites contained lamella structures and deformed nuclei, (3) trophozoites displayed dissolved cytoplasm with large vacuole spaces or decreased cytoplasmic volume, (4) adhesive disc bubbles or the lamella structures of cytoplasm were clearly observed, and (5) cell division was arrested. Using microscopy and cytometry techniques, we demonstrate that changes in G. lamblia morphology and cell cycle state were induced by DHA.

Mebendazole in parasitic infections other than those caused by soil-transmitted helminths

Mebendazole, a benzimidazole carbamate compound, is currently in use for human medical practice against soil-transmitted helminthiasis (STH) and enterobiasis. However, it has been demonstrated that its spectrum of activity is broad and goes beyond those infections. Several studies provide evidence that this drug, taken at higher doses than used for STH and enterobiasis, could be sufficiently effective on some protozoa, nematodes and cestodes.

Giardiasis: a pharmacotherapy review

Giardia lamblia, the cause of human giardiasis, is among the most common intestinal protozoa worldwide. Human infection may range from asymptomatic shedding of giardial cysts to symptomatic giardiasis, being responsible for abdominal cramps, nausea, acute or chronic diarrhoea, with malabsorption and failure of children to thrive. At present, treatment options include the nitroimidazoles derivatives; especially metronidazole, which has been the mainstay of treatment for decades and is still widely used. The increasing number of reports of refractory cases with this group of drugs and other antigiardial agents, has raised concern and led to a search for other compounds, some of which have arisen due to the introduction of drugs initially addressed to other diseases. The present article examines some of the most important points of antigiardial pharmacotherapy available at present and the future prospects of development of new agents.

WITHDRAWN: Drugs for treating giardiasis

BACKGROUND

There can be a high rate of recurrence of disease after initial drug treatment for giardiasis. These drugs also have a range of adverse effects.

OBJECTIVES

The objective of this review was to assess the effects of drug treatments for giardiasis.

SEARCH STRATEGY

We searched the Cochrane Infectious Diseases Group Specialized Register, CENTRAL, MEDLINE, EMBASE, Current Contents, and reference lists of articles.

SELECTION CRITERIA

Randomised and quasi-randomised trials of drug therapy for giardiasis compared with placebo or another drug.

DATA COLLECTION AND ANALYSIS

Two reviewers independently assessed trial quality and extracted data.

MAIN RESULTS

Thirty-four trials were included. Only one trial was without serious methodological flaws. Compared with placebo, drug treatment was associated with an improved cure rate (odds ratio 11.51, 95% confidence interval 2.29 to 57.98). Metronidazole treatment longer than three days had a better parasitological cure rate than other long treatment courses (odds ratio 2.41, 95% confidence interval 1.31 to 4.44), but there was significant heterogeneity between the trials. Available evidence has not detected a difference in cure between single dose therapy and longer treatment courses (odds ratio 0.33, 95% confidence interval 0.08 to 1.34). Within the single dose regimens, the available evidence did not demonstrate a difference in parasitological cure rate between tinidazole and other short therapies (odds ratio 3.39, 95% confidence interval 0.95 to 12.04), but had a higher clinical cure rate (odds ratio 5.33, 95% 2.66 to 10.67).

AUTHORS' CONCLUSIONS

A single dose of tinidazole appears to give the highest clinical cure rate for giardiasis with relatively few adverse effects.

A randomized, controlled, open-label trial of a single day of mebendazole versus a single dose of tinidazole in the treatment of giardiasis in children

BACKGROUND

Giardia duodenalis is the most commonly detected parasite in the intestinal tract of humans and 5-nitroimidazole compounds, quinacrine and furazolidone have been used against giardiasis. However, cases refractory to treatment with these drugs are becoming more common worldwide.

OBJECTIVE

To compare the efficacy and safety of mebendazole versus tinidazole in the treatment of giardiasis.

RESEARCH DESIGN AND METHODS

122 children (aged 5 to 15 years) of both sexes with confirmed Giardia duodenalis cysts or trophozoites in their stool samples were randomly separated into two groups of 61 individuals. Each group received either mebendazole 200 mg three times for 1 day or tinidazole 50 mg/kg in a single dose. The evaluation of the efficacy was based on parasitological response. Parents or legal guardians of each child were asked to provide three fecal samples on days 3, 5, and 7 after treatment completion. A child was considered to be cured if no Giardia trophozoites or cysts were found in any of the three post-treatment fecal specimens evaluated by direct wet mounts and/or after Ritchie concentration techniques.

RESULTS

The frequency of cure was higher for tinidazole (81.97%) than for mebendazole (63.93%); the difference was statistically significant (p < 0.05). Transient abdominal pain was more common in children treated with mebendazole (p < 0.05), whereas loss of appetite, bitter taste, headache, vomiting, and nausea were more common in the tinidazole-treated group (p < 0.05).

CONCLUSIONS

Three doses of mebendazole, in a single day, are inferior to a single dose tinidazole in the treatment of giardiasis.

Randomized clinical study of five days apostrophe therapy with mebendazole compared to quinacrine in the treatment of symptomatic giardiasis in children

AIM: To compare the efficacy and safety of five days apostrophe therapy of mebendazole (MBZ) versus quinacrine (QC) on human giardiasis in children.

METHODS: A clinical trial was carried out in paediatric patients (aged 5-15 years) with confirmed symptomatic G. duodenalis mono-infection. Patients were randomly assigned to receive either MBZ [200 mg taken three times per day (TID) (n = 61)] or QC [2 mg/kg bodyweight tid (n = 61)], both for five days. Follow-up faecal samples were obtained at 3, 5 and 7 d after the end of the treatment.

RESULTS: Although the frequency of cure was higher for QC (83.6%) than for MBZ (78.7%), the difference was not statistically significant (P > 0.05). Adverse events were reported more in the QC group (P < 0.05), all of them transient and self-limiting.

CONCLUSION: Despite final cure rates ocurring lower than expected, the overall results of this study reconfirmed the efficacy of MBZ in giardiasis and also indicate that, although comparable to QC, at least in this setting the 5 d course of MBZ did not appear to improve the cure rates in this intestinal parasitic infection.