Effect of drug metabolism in the treatment of SARS-CoV-2 from an entirely computational perspective.

Understanding the effects of metabolism on the rational design of novel and more effective drugs is still a considerable challenge. To the best of our knowledge, there are no entirely computational strategies that make it possible to predict these effects. From this perspective, the development of such methodologies could contribute to significantly reduce the side effects of medicines, leading to the emergence of more effective and safer drugs. Thereby, in this study, our strategy is based on simulating the electron ionization mass spectrometry (EI-MS) fragmentation of the drug molecules and combined with molecular docking and ADMET models in two different situations. In the first model, the drug is docked without considering the possible metabolic effects. In the second model, each of the intermediates from the EI-MS results is docked, and metabolism occurs before the drug accesses the biological target. As a proof of concept, in this work, we investigate the main antiviral drugs used in clinical research to treat COVID-19. As a result, our strategy made it possible to assess the biological activity and toxicity of all potential by-products. We believed that our findings provide new chemical insights that can benefit the rational development of novel drugs in the future.

Edoxaban versus Vitamin K Antagonist for Atrial Fibrillation after TAVR.

BACKGROUND: The role of direct oral anticoagulants as compared with vitamin K antagonists for atrial fibrillation after successful transcatheter aortic-valve replacement (TAVR) has not been well studied. METHODS: We conducted a multicenter, prospective, randomized, open-label, adjudicator-masked trial comparing edoxaban with vitamin K antagonists in patients with prevalent or incident atrial fibrillation as the indication for oral anticoagulation after successful TAVR. The primary efficacy outcome was a composite of adverse events consisting of death from any cause, myocardial infarction, ischemic stroke, systemic thromboembolism, valve thrombosis, or major bleeding. The primary safety outcome was major bleeding. On the basis of a hierarchical testing plan, the primary efficacy and safety outcomes were tested sequentially for noninferiority, with noninferiority of edoxaban established if the upper boundary of the 95% confidence interval for the hazard ratio did not exceed 1.38. Superiority testing of edoxaban for efficacy would follow if noninferiority and superiority were established for major bleeding. RESULTS: A total of 1426 patients were enrolled (713 in each group). The mean age of the patients was 82.1 years, and 47.5% of the patients were women. Almost all the patients had atrial fibrillation before TAVR. The rate of the composite primary efficacy outcome was 17.3 per 100 person-years in the edoxaban group and 16.5 per 100 person-years in the vitamin K antagonist group (hazard ratio, 1.05; 95% confidence interval [CI], 0.85 to 1.31; P = 0.01 for noninferiority). Rates of major bleeding were 9.7 per 100 person-years and 7.0 per 100 person-years, respectively (hazard ratio, 1.40; 95% CI, 1.03 to 1.91; P = 0.93 for noninferiority); the difference between groups was mainly due to more gastrointestinal bleeding with edoxaban. Rates of death from any cause or stroke were 10.0 per 100 person-years in the edoxaban group and 11.7 per 100 person-years in the vitamin K antagonist group (hazard ratio, 0.85; 95% CI, 0.66 to 1.11). CONCLUSIONS: In patients with mainly prevalent atrial fibrillation who underwent successful TAVR, edoxaban was noninferior to vitamin K antagonists as determined by a hazard ratio margin of 38% for a composite primary outcome of adverse clinical events. The incidence of major bleeding was higher with edoxaban than with vitamin K antagonists. (Funded by Daiichi Sankyo; ENVISAGE-TAVI AF ClinicalTrials.gov number, NCT02943785.).

Thiamethoxam exposure deregulates short ORF gene expression in the honey bee and compromises immune response to bacteria.

Maximizing crop yields relies on the use of agrochemicals to control insect pests. One of the most widely used classes of insecticides are neonicotinoids that interfere with signalling of the neurotransmitter acetylcholine, but these can also disrupt crop-pollination services provided by bees. Here, we analysed whether chronic low dose long-term exposure to the neonicotinoid thiamethoxam alters gene expression and alternative splicing in brains of Africanized honey bees, Apis mellifera, as adaptation to altered neuronal signalling. We find differentially regulated genes that show concentration-dependent responses to thiamethoxam, but no changes in alternative splicing. Most differentially expressed genes have no annotated function but encode short Open Reading Frames, a characteristic feature of anti-microbial peptides. As this suggested that immune responses may be compromised by thiamethoxam exposure, we tested the impact of thiamethoxam on bee immunity by injecting bacteria. We show that intrinsically sub-lethal thiamethoxam exposure makes bees more vulnerable to normally non-pathogenic bacteria. Our findings imply a synergistic mechanism for the observed bee population declines that concern agriculturists, conservation ecologists and the public.

In vivo demonstration of immunologic cross-reactivity to octylisothiazolinone in patients primarily and strongly sensitized to methylisothiazolinone.

BACKGROUND: Notwithstanding that concomitant exposure to different isothiazolinone derivatives may result in concomitant sensitization, clinical and animal studies have suggested cross-reactivity between these derivatives, notably between methylisothiazolinone (MI) and octylisothiazolinone (OIT). OBJECTIVE: To investigate if patients sensitized to MI show cross-reactions to OIT and/or to benzisothiazolinone (BIT) by applying the concept of the re-test method. PATIENTS AND METHODS: From March to October 2019 consecutive patients were patch tested with MI 0.2% aqueous in duplicate at the two lower corners of both shoulder blades. Patients sensitized to MI, but not to OIT 0.1% petrolatum (pet.) nor to BIT 0.1% pet., were re-tested, 2 months later, with the latter two derivatives at the skin sites where the MI reactions had fully disappeared. RESULTS: Of 116 patients, 15 (13%) were sensitized to MI, eight of these not sensitized to BIT nor to OIT. Of these, seven patients, all (very) strongly sensitized to MI, were re-tested: five patients showed positive patch test reactions to OIT 0.1% pet.; one patient to OIT 0.1% pet. and BIT 0.1% pet.; and one other patient showed no reactions. CONCLUSION: This study suggests that patients primarily and strongly sensitized to MI may show immunologic cross-reactions to OIT, and to a far lesser extent to BIT.

High rate of sensitization to Kathon CG, detected by patch tests in patients with suspected allergic contact dermatitis.

BACKGROUND: Kathon CG, a combination of methylchloroisothiazolinone and methylisothiazolinone, is widely used as preservative in cosmetics, as well in household cleaning products, industrial products such as paints and glues. It has emerged as an important sensitizing agent in allergic contact dermatitis. OBJECTIVES: This study evaluated the reactivity to this substance in patients subjected to patch tests at the Dermatology Institute in Bauru, São Paulo from 2015 to 2017 and its correlation with other preservatives, the professional activity and location of the lesions. METHODS: The patients were submitted to standard series of epicutaneous tests, standardized by the Brazilian Group Studies on Contact Dermatitis. RESULTS: Out the 267 patients tested, 192 presented positivity to at least one substance and 29 of the patients (15.10%) presented reaction to Kathon CG, with predominance of the female gender (n=27); main professional activity associated with Kathon CG sensibilization was cleaning (17.24%), followed by aesthetic areas (13.79%) and health care (10.34%). The most prevalent sensitizations among the substances tested were nickel sulphate (56.3%), followed by cobalt chloride (23.4%), neomycin (18.2%), potassium dichromate (17.7%), thimerosal (14.5%), formaldehyde (13.2%), paraphenylenediamine (9.3%), and fragrance mix (8.3%). STUDY LIMITATIONS: We do not have data from patients that were submitted to patch test a decade ago in order to confront to current data and establish whether or no sensitization to Kathon CG has increased. CONCLUSION: High positivity to Kathon CG corroborates the recent findings in the literature, suggesting more attention to concentration of this substance, used in cosmetics and products for domestic use.

High rate of sensitization to Kathon CG, detected by patch tests in patients with suspected allergic contact dermatitis

Abstract Background: Kathon CG, a combination of methylchloroisothiazolinone and methylisothiazolinone, is widely used as preservative in cosmetics, as well in household cleaning products, industrial products such as paints and glues. It has emerged as an important sensitizing agent in allergic contact dermatitis. Objectives: This study evaluated the reactivity to this substance in patients subjected to patch tests at the Dermatology Institute in Bauru, São Paulo from 2015 to 2017 and its correlation with other preservatives, the professional activity and location of the lesions. Methods: The patients were submitted to standard series of epicutaneous tests, standardized by the Brazilian Group Studies on Contact Dermatitis. Results: Out the 267 patients tested, 192 presented positivity to at least one substance and 29 of the patients (15.10%) presented reaction to Kathon CG, with predominance of the female gender (n = 27); main professional activity associated with Kathon CG sensibilization was cleaning (17.24%), followed by aesthetic areas (13.79%) and health care (10.34%). The most prevalent sensitizations among the substances tested were nickel sulphate (56.3%), followed by cobalt chloride (23.4%), neomycin (18.2%), potassium dichromate (17.7%), thimerosal (14.5%), formaldehyde (13.2%), paraphenylenediamine (9.3%), and fragrance mix (8.3%). Study limitations: We do not have data from patients that were submitted to patch test a decade ago in order to confront to current data and establish whether or no sensitization to Kathon CG has increased. Conclusion: High positivity to Kathon CG corroborates the recent findings in the literature, suggesting more attention to concentration of this substance, used in cosmetics and products for domestic use.

Early Bactericidal Activity Trial of Nitazoxanide for Pulmonary Tuberculosis.

This study was conducted in treatment-naive adults with drug-susceptible pulmonary tuberculosis in Port-au-Prince, Haiti, to assess the safety, bactericidal activity, and pharmacokinetics of nitazoxanide (NTZ). This was a prospective phase II clinical trial in 30 adults with pulmonary tuberculosis. Twenty participants received 1 g of NTZ orally twice daily for 14 days. A control group of 10 participants received standard therapy over 14 days. The primary outcome was the change in time to culture positivity (TTP) in an automated liquid culture system. The most common adverse events seen in the NTZ group were gastrointestinal complaints and headache. The mean change in TTP in sputum over 14 days in the NTZ group was 3.2 h ± 22.6 h and was not statistically significant (P = 0.56). The mean change in TTP in the standard therapy group was significantly increased, at 134 h ± 45.2 h (P < 0.0001). The mean NTZ MIC for Mycobacterium tuberculosis isolates was 12.3 µg/ml; the mean NTZ maximum concentration (Cmax) in plasma was 10.2 µg/ml. Negligible NTZ levels were measured in sputum. At the doses used, NTZ did not show bactericidal activity against M. tuberculosis Plasma concentrations of NTZ were below the MIC, and its negligible accumulation in pulmonary sites may explain the lack of bactericidal activity. (This study has been registered at ClinicalTrials.gov under identifier NCT02684240.).

Proinflammatory and regulatory mechanisms in allergic contact dermatitis caused by methylchloroisothiazolinone and methylisothiazolinone.

BACKGROUND: Methylchloroisothiazolinone (MCI) and methylisothiazolinone (MI) are the cause of an increasing number of contact allergies. Understanding the mechanisms by which MCI/MI induces proinflammatory and regulatory factors production is necessary to understand the outcome of allergic contact dermatitis (ACD). OBJECTIVES: To evaluate the dysfunction of proinflammatory cytokines and regulatory factors in the positive MCI/MI patch test at the transcriptional and protein expression levels. Moreover, to analyse the cytokines production induced by MI in peripheral blood mononuclear cells (PBMCs). MATERIALS AND METHODS: The selected patients had positive MCI/MI patch test results. The expression of proinflammatory factors was evaluated by q-PCR and immunochemistry at 48 hours of positive MCI/MI patch test. The MCI/MI- or MI- induced secretion of IL-1ß, TNF and IL-6 by PBMC was analysed by flow cytometry. RESULTS: The results showed a decreased TLR4 expression with upregulated IL6, FOXP3, IL10 and TGFß mRNA expression as assessed by q-PCR at the site of the MCI/MI skin reaction. We detected increased protein levels of TLR4, FOXP3 and IL-10 in the dermis layer in the ACD reaction by immunocitochemistry. Moreover, MCI/MI induced proinflammatory cytokine production by PBMC through the NF-κB signalling pathway. CONCLUSION: Considering the altered innate immune response triggered by MCI/MI sensitization, these findings indicate that the regulatory process at the induction phase of ACD is a crucial mechanism. Given the increase in occupational and domestic exposure to MCI/MI, the underlying immunological mechanisms should be understood.

Efficacy and safety of edoxaban compared with warfarin according to the burden of diseases in patients with atrial fibrillation: insights from the ENGAGE AF-TIMI 48 trial.

AIMS: Non-vitamin K antagonist oral anticoagulants represent a new option for prevention of embolic events in patients with atrial fibrillation (AF). However, little is known about the impact of non-cardiac comorbidities on the efficacy and safety profile of these drugs. METHODS AND RESULTS: In a post hoc analysis of the ENGAGE AF-TIMI 48 trial, we analysed 21 105 patients with AF followed for an average of 2.8 years and randomized to either a higher-dose edoxaban regimen (HDER), a lower-dose edoxaban regimen, or warfarin. We used the updated Charlson Comorbidity Index (CCI) to stratify the patients according to the burden of concomitant disease (CCI = 0, 1, 2, 3, and ≥4). The treatment groups were then compared for safety, efficacy, and net clinical outcomes across CCI categories. There were 32.0%, 7.3%, 42.1%, 12.7%, and 6.0% of patients with CCI scores of 0, 1, 2, 3, and ≥4, respectively. A CCI score ≥4 was associated with significantly higher rates of thromboembolic events, bleeding, and death compared to CCI = 0 (P < 0.05 for each). The annualized rates of the primary net clinical outcome (stroke/systemic embolism, major bleeding, or death) for CCI = 0, 1, 2, 3, or ≥4 were 5.9%, 8.7%, 6.6%, 10.3%, and 13.6% (Ptrend < 0.001). There were no significant interactions between treatment with HDER vs. warfarin and efficacy, safety, and net outcomes across the CCI groups (P-interaction > 0.10 for each). CONCLUSION: Although increasing CCI scores are associated with worse outcomes, the efficacy, safety, and net clinical outcomes of edoxaban vs. warfarin were independent of the degree of comorbidity present.

[Management of bleeding associated with direct oral anticoagulants: update on reversal strategies]. / Manejo de hemorragia asociada a anticoagulantes orales directos: estado actual de las estrategias de reversión.

Direct oral anticoagulants (DOACs), including the direct thrombin inhibitor dabigatran and the direct factor Xa inhibitors rivaroxaban, apixaban and edoxaban have at least comparable efficacy as vitamin K antagonists along with a better safety profile, reflected by a lower incidence of intracranial hemorrhage. Specific reversal agents have been developed in recent years. Namely, idarucizumab, a specific antidote for dabigatran, is currently approved in most countries. Andexanet, which reverses factor Xa inhibitors, has been recently approved by the FDA, and ciraparantag, a universal antidote targeted to reverse all DOACs, is still under investigation. In this review we provide an update on the pharmacology of DOACs, the risk of hemorrhagic complications associated with their use, the measurement of their anticoagulant effect and the reversal strategies in case of DOAC-associated bleeding.

Efficacy and Safety of Nitazoxanide in Addition to Standard of Care for the Treatment of Severe Acute Respiratory Illness.

BACKGROUND: Effective therapeutics for respiratory viruses are needed. Early data suggest that nitazoxanide (NTZ) may be beneficial for treating acute respiratory viral illness. METHODS: From March 2014 through March 2017, a double-blind, placebo-controlled trial was conducted in 260 participants ≥1 year old hospitalized with influenza-like illness at 6 hospitals in Mexico. Participants were randomized 1:1 to NTZ (age ≥12 years, 600 mg twice daily; age 4-11 years and 1-3 years, 200 or 100 mg twice daily, respectively) or placebo for 5 days in addition to standard of care. The primary endpoint was time from first dose to hospital discharge. Influenza reverse-transcription polymerase chain reaction and Respifinder 22 multiplex test were used for virus detection. RESULTS: Of 260 participants enrolled, 257 were randomized and took at least 1 dose of study treatment (intention-to-treat population): 130 in the NTZ group and 127 in the placebo group. The Kaplan-Meier estimate of the median duration of hospitalization was 6.5 (interquartile range [IQR], 4.0-9.0) days in the NTZ group vs 7.0 (IQR, 4.0-9.0) days in the placebo group (P = .56). Duration of hospitalization between the 2 treatments was similar in children (P = .29) and adults (P = .62), influenza A and B (P = .32), and other respiratory viruses. Seven (5.4%) and 6 (4.7%) participants in the NTZ and placebo groups, respectively, reported serious adverse events. CONCLUSIONS: Treatment with NTZ did not reduce the duration of hospital stay in severe influenza-like illness. Further analyses based on age and evaluations by virus did not reveal any subgroups that appeared to benefit from NTZ. CLINICAL TRIALS REGISTRATION: NCT02057757.

Manejo de hemorragia asociada a anticoagulantes orales directos: estado actual de las estrategias de reversión / Management of bleeding associated with direct oral anticoagulants: update on reversal strategies

Direct oral anticoagulants (DOACs), including the direct thrombin inhibitor dabigatran and the direct factor Xa inhibitors rivaroxaban, apixaban and edoxaban have at least comparable efficacy as vitamin K antagonists along with a better safety profile, reflected by a lower incidence of intracranial hemorrhage. Specific reversal agents have been developed in recent years. Namely, idarucizumab, a specific antidote for dabigatran, is currently approved in most countries. Andexanet, which reverses factor Xa inhibitors, has been recently approved by the FDA, and ciraparantag, a universal antidote targeted to reverse all DOACs, is still under investigation. In this review we provide an update on the pharmacology of DOACs, the risk of hemorrhagic complications associated with their use, the measurement of their anticoagulant effect and the reversal strategies in case of DOAC-associated bleeding.

Edoxaban for Venous Thromboembolism Treatment-The New Kid on The Block for Latin America. A Practical Guide.

Edoxaban, a direct factor Xa inhibitor (FXa), is the fourth direct oral anticoagulant (DOAC) approved for clinical use in the treatment of venous thromboembolism (VTE) in Latin America, following global approvals for this indication. Edoxaban features some particular characteristics when compared to the previously approved DOACs. This review summarizes the main properties of edoxaban, the outcomes results of its pivotal global clinical trials and the peculiar clinical features of this compound. This practical guide aims to help Latin America clinicians understand edoxaban, its proper indication and its use for the appropriate patients with VTE.

Toxic Myopathy due to Antidopaminergic Medication Without Neuroleptic Malignant Syndrome.

Severe recurrent proximal muscle weakness without neuroleptic malignant syndrome secondary to antidopaminergic medication has rarely been reported. We report a 29-year-old man with history of obsessive compulsive disorder and Tourette syndrome who presented with 2 months of worsening dyspnea 3 weeks after starting ziprasidone 40 mg daily that required mechanical ventilation. A year before, after an increased risperidone dose from 0.5 to 1 mg daily, he had developed proximal muscle weakness that spontaneously improved 2 months after discontinuation of risperidone. On this admission, his creatine kinase (CK) was 3318 units/L, and ziprasidone was discontinued. He fully recovered 2 months after discontinuation of ziprasidone, and his CK was 62 units/L. Genetic testing for limb-girdle muscular dystrophy was negative. This case highlights the importance of evaluating CK level in patients taking antidopaminergic medication with any suggestion of muscle weakness to prevent potentially life-threatening complication.

Treatment of adult chronic indeterminate Chagas disease with benznidazole and three E1224 dosing regimens: a proof-of-concept, randomised, placebo-controlled trial.

BACKGROUND: Chagas disease is a major neglected vector-borne disease. In this study, we investigated the safety and efficacy of three oral E1224 (a water-soluble ravuconazole prodrug) regimens and benznidazole versus placebo in adult chronic indeterminate Chagas disease. METHOD: In this proof-of-concept, double-blind, randomised phase 2 clinical trial, we recruited adults (18-50 years) with confirmed diagnosis of Trypanosoma cruzi infection from two outpatient units in Bolivia. Patients were randomised with a computer-generated randomisation list, which was stratified by centre and used a block size of ten. Patients were randomly assigned (1:1:1:1:1) to five oral treatment groups: high-dose E1224 (duration 8 weeks, total dose 4000 mg), low-dose E1224 (8 weeks, 2000 mg), short-dose E1224 (4 weeks + 4 weeks placebo, 2400 mg), benznidazole (60 days, 5 mg/kg per day), or placebo (8 weeks, E1224-matched tablets). Double-blinding was limited to the E1224 and placebo arms, and assessors were masked to all treatment allocations. The primary efficacy endpoint was parasitological response to E1224 at the end of treatment, assessed by PCR. The secondary efficacy endpoints were parasitological response to benznidazole at end of treatment, assessed by PCR; sustainability of parasitological response until 12 months; parasite clearance and changes in parasite load; incidence of conversion to negative response in conventional and non-conventional (antigen trypomastigote chemiluminescent ELISA [AT CL-ELISA]) serological response; changes in levels of biomarkers; and complete response. The primary analysis population consisted of all randomised patients by their assigned treatment arms. This trial is registered with ClinicalTrials.gov, number NCT01489228. FINDINGS: Between July 19, 2011, and July 26, 2012, we screened 560 participants with confirmed Chagas disease, of whom 231 were enrolled and assigned to high-dose E1224 (n=45), low-dose E1224 (n=48), short-dose E1224 (n=46), benznidazole (n=45), or placebo (n=47). Parasite clearance was observed with E1224 during the treatment phase, but no sustained response was seen with low-dose and short-dose regimens, whereas 13 patients (29%, 95% CI 16·4-44·3) had sustained response with the high-dose regimen compared with four (9%, 2·4-20·4) in the placebo group (p<0·0001). Benznidazole had a rapid and sustained effect on parasite clearance, with 37 patients (82%, 67·9-92·0) with sustained response at 12-month follow-up. After 1 week of treatment, mean quantitative PCR repeated measurements showed a significant reduction in parasite load in all treatment arms versus placebo. Parasite levels in the low-dose and short-dose E1224 groups gradually returned to placebo levels. Both treatments were well tolerated. Reversible, dose-dependent liver enzyme increases were seen with E1224 and benznidazole. 187 (81%) participants developed treatment-emergent adverse events and six (3%) developed treatment-emergent serious adverse events. Treatment-emergent adverse events were headaches, nausea, pruritus, peripheral neuropathy, and hypersensitivity. INTERPRETATION: E1224 is the first new chemical entity developed for Chagas disease in decades. E1224 displayed a transient, suppressive effect on parasite clearance, whereas benznidazole showed early and sustained efficacy until 12 months of follow-up. Despite PCR limitations, our results support increased diagnosis and access to benznidazole standard regimen, and provide a development roadmap for novel benznidazole regimens in monotherapy and in combinations with E1224. FUNDING: Drugs for Neglected Diseases initiative.

Ziprasidone, a second-generation antipsychotic drug, triggers a macrophage inflammatory response in vitro.

Antipsychotic drugs are used to treat schizophrenia and other psychiatric disorders. However, most of these drugs present side effects causing obesity and other serious metabolic alterations that correlate with grade of chronic inflammation. In contrast, ziprasidone's (ZIP) metabolic side effects are attenuated relative to those of other antipsychotic drugs, but some reports suggest that this drug could cause allergic, hypersensitive reactions in susceptible patients. At present, the mechanism of ZIP's effect on peripheral inflammatory metabolism is not well characterized. We conducted an in vitro study to evaluate the effect of ZIP on a macrophage cell line (RAW 264.1). Our results showed that in non-activated macrophage cells, ZIP exposure initiated macrophage spreading; increased cellular proliferation, as evaluated by MTT and flow cytometry assays; and presented higher levels of oxidant molecules involved in the inflammatory response (nitric oxide, superoxide, reactive oxygen species), and proinflammatory cytokines (IL-1, IL-6, TNFα, INFγ). Levels of IL-10, an anti-inflammatory cytokine were lower in ZIP-exposed cells. These effects were less potent than those caused by the positive control for inflammation induction (phytohemagglutinin), and more intense than the effects of lithium (LI), which was used as an anti-inflammatory molecule. ZIP also modulated cytokine gene expression. Taken together, these data suggest that ZIP can produce a peripheral inflammatory response, and this response may explain the allergen-inflammatory response observed in some patients treated with this antipsychotic drug.

Efficacy of nitazoxanide to treat natural Giardia infections in dogs.

BACKGROUND: Giardia parasites cause gastrointestinal disease in humans, dogs, and many other animals worldwide. The treatment of dogs for giardiasis requires further investigation to ascertain levels of drug efficacy and the possibility of adverse side effects. Nitazoxanide (NTZ) has shown good clinical anti-Giardia activity in humans, yet it has not been evaluated for the treatment of giardiasis in dogs. METHODS: Thirty-five dogs, naturally infected with Giardia were divided into five groups (n = 7): dogs in group NTZ1, NTZ2, and NTZ3 were treated with a single oral dose of 37.5 mg/kg, 75 mg/kg, and 150 mg/kg, respectively, of NTZ on days 0 and 14. The fourth group was treated with a commercially available regimen that includes a combination of pyrantel, praziquantel, and febantel (FEB) administered orally for three consecutive days. Additionally, an untreated control group was established. Giardia cysts from the stool of each dog were quantified on days -3, 0, 5, 7, 9, 11, 14, 18, 25, and 28. Biochemical parameters were evaluated in all dogs, before the first treatment and after concluding the experiment. RESULTS: Shedding of Giardia cysts was reduced in all treated groups when compared to untreated controls (P < 0.01). However, NTZ2, NTZ3, and FEB had a lower risk during the study. Furthermore, NTZ was also effective against another protozoan, Cryptosporidium spp. at doses of 75 mg/kg and 150 mg/kg, in contrast to the combination of febantel + pyrantel + praziquantel. Biochemical parameters of treated animals, namely, aspartate transaminase and alanine transaminase enzymes, remained within physiological ranges. CONCLUSIONS: Based on these results, the implementation of NTZ as a treatment for giardiasis in dogs is proposed. The administration of a single dose is an important advantage of NTZ because it reduces workload, particularly in animals placed in shelters and kennels, where handling of large numbers of animals is required, and personnel is frequently scarce.