Rifampicin remains one of the first-line drugs used in tuberculosis therapy. This drug´s potential to induce the hepatic cytochrome P450 oxidative enzyme system increases the risk of drug-drug interactions. Thus, although the presence of comorbidities typically necessitates the use of multiple drugs, the co-administration of rifampicin and warfarin may lead to adverse drug events. We report a bleeding episode after termination of the co-administration of rifampicin and warfarin and detail the challenges related to international normalized ratio (INR) monitoring.

Objective Health literacy has been related to health-related conditions and health outcomes. Studies examining the association of health literacy and anticoagulation have had variable results. We sought to investigate the relations of health literacy and percentage of time in therapeutic range (TTR) in a vulnerable Brazilian cohort at two hospital-based anticoagulation clinics. Methods We measured health literacy with the Short Assessment of Health Literacy for Portuguese-speaking Adults (SAHLPA-18) in 2015–2016. We identified the demographic and clinical characteristics associated with health literacy and related health literacy to TTR. Results We enrolled 422 adults prescribed chronic warfarin therapy in our observational study (median age 62.1 years; 58.8% women; monthly income $200.00). The prevalence of inadequate health literacy (score 0–14 points) was 72.3% with a median score of 12 (quartiles, Q1=10; Q3=15) on the SAHLPA-18. The median TTR was 66.1%. In the multivariable logistic analysis, cognitive impairment and assistance with taking warfarin were associated with inadequate health literacy. Prosthetic heart valves and more school years were associated with adequate health literacy. Our analyses showed no significant relation between health literacy and TTR, analysing health literacy as a categorical (adjusted OR 1.05; 95% CI 0.65 to 1.70) or continuous variable (Spearman’s coefficient 0.02; p=0.70). Conclusions Inadequate health literacy was highly prevalent in this impoverished Brazilian cohort receiving anticoagulation with warfarin. However, we did not identify an association between health literacy and TTR. Future investigations may consider the systemic factors that contribute towards successful anticoagulation outcomes for vulnerable patient cohorts with inadequate health literacy.

: Hospitalized patients require the use of a variety of drugs, many of which individually or in combination have the potential to cause kidney damage. The use of potentially nephrotoxic drugs is often unavoidable, and the need for dose adjustment should be evaluated. This study is aimed at assessing concordance in information on drug-induced nephrotoxicity and dose adjustment recommendations by comparing four drug information sources (DRUGDEX^®, UpToDate^®, Medscape^® and the Brazilian Therapeutic Formulary) using the formulary of a Brazilian public hospital. A total of 218 drugs were investigated. The global Fleiss’ kappa coefficient was 0.265 for nephrotoxicity (p < 0.001; CI 95%, 0.211–0.319) and 0.346 for recommendations (p < 0.001; CI 95%, 0.292–0.401), indicating fair concordance among the sources. Anti-infectives and anti-hypertensives were the main drugs cited as nephrotoxic by the different sources. There were no clear definitions for qualitative data or quantitative values for dose adjustments among the four information sources. There was no advice for dosing for a large number of the drugs in the international databases. The National Therapeutic Formulary offered imprecise dose adjustment recommendations for many nephrotoxic drugs. Discrepancies among information sources may have a clinical impact on patient care and contribute to drug-related morbidity and mortality.