Determinants of adverse reactions to first-line antitubercular medicines: a prospective cohort study

Sex-dependent variability of isoniazid and rifampicin serum levels in patients with tuberculosis

INTRODUCTION

Drug-sensitive TB (DS-TB) is treated with isoniazid, rifampicin, ethambutol, and pyrazinamide. Factors like fast-metabolizing enzymes, malabsorption, and drug interactions can influence serum drug levels. Current TB treatment guidelines recommend weight-adapted dosing without considering sex differences. This study examines drug levels of isoniazid and rifampicin in TB patients treated between 2019 and 2023 at our center focusing on sex-specific aspects.

METHODS

Patients diagnosed with TB and available serum levels of isoniazid or rifampicin between 2019 and 2023 were retrospectively identified. Serum levels were measured using liquid chromatography-mass spectrometry and high-performance liquid chromatography. Patients were stratified by sex and a linear regression mixed effect model was used to assess predictors for different serum levels.

RESULTS

The study included 281 single therapeutic drug monitoring (TDM) measurements from 59 patients (28 women, 47.5%). For isoniazid, no sex-specific differences in serum drug levels were identified. On the other hand, female sex was a significant predictor of higher rifampicin plasma levels (coefficient 4.16, 95% CI 0.74-7.59, p = 0.009). Only 38.2% of rifampicin serum level measurements in male patients were within target range, the majority (40/68, 58.8%) were below range and only 2 (2.9%) TDM-levels were above range. Women displayed higher overall rifampicin serum levels than men (median 13.7 mg/l vs. 7.1 mg/l, p = 0.04), although weight adjusted doses were not significantly different (median 10.0 mg/kg vs. 9.8 mg/kg p = 0.56). Adverse effects were noted in 42.9% (42/98) of measurements in women and 29.5% (54/183) of measurements in men (p = 0.03).

DISCUSSION

Rifampicin levels were significantly lower in men compared to women, despite weight-adjusted dosing. Clinicians should consider TDM and potential sex differences when treating patients with TB.

Isoniazid-induced pancreatitis: A systematic review

BACKGROUND

Isoniazid-induced pancreatitis is a potentially serious adverse drug reaction, however, the frequency of its occurrence is unknown. We conducted a systematic review to explore this adverse drug reaction comprehensively.

METHODS

We performed an advanced search in PubMed, Web of Science, Scopus, Ovid, and Embase for studies that reported isoniazid-induced pancreatitis. From the extracted data of eligible cases, we performed a descriptive analysis and a methodological risk of bias assessment using a standardized tool.

RESULTS

We included 16 case reports from eight countries comprising 16 patients in our systematic review. Most of the isoniazid-induced pancreatitis cases were extrapulmonary tuberculosis cases. We found the mean age across all case reports was 36.7 years. In all the cases, discontinuation of isoniazid resulted in the resolution of pancreatitis.

CONCLUSIONS

We found the latency period for isoniazid-induced pancreatitis to be ranged from 12 to 45 days after initiation of isoniazid therapy. A low threshold for screening of pancreatitis by measuring pancreatic enzymes in patients on isoniazid presenting with acute abdominal pain is recommended. This would facilitate an early diagnosis and discontinuation of isoniazid, thus reducing the severity of pancreatitis and preventing the complications of pancreatitis.

Drug-induced hypothyroidism in tuberculosis

INTRODUCTION

Adverse reactions to tuberculosis treatment can impact patient adherence and prognosis. Hypothyroidism is a frequent adverse reaction caused using ethionamide, prothionamide, and para-aminosalicylic acid and is often underdiagnosed.

AREAS COVERED

We searched Scielo, Scopus, and EMBASE databases, including 67 articles. Antitubercular drug-induced hypothyroidism has a prevalence of 17%. It occurs after 2 to 3 months of treatment and resolves within 4 to 6 weeks after discontinuation. It is postulated to result from the inhibition of thyroperoxidase function, blocking thyroid hormone synthesis. Symptoms are nonspecific, necessitating individualized thyroid-stimulating hormone measurement for detection. Specific guidelines for management are lacking, but initiation of treatment with levothyroxine, as is customary for primary hypothyroidism, is recommended. Discontinuation of antitubercular drugs is discouraged, as it may lead to unfavorable consequences.

EXPERT OPINION

Antitubercular drug-induced hypothyroidism is more common than previously thought, affecting one in six MDR-TB patients. Despite diagnostic and treatment recommendations, implementation is hindered in low-income countries due to the lack of certified laboratories. New drugs for tuberculosis treatment may affect thyroid function, requiring vigilant monitoring for complications, including hypothyroidism.

Influence of sex on the exposure to isoniazid in patients with pulmonary tuberculosis

Isoniazid is a key component of tuberculosis treatment. Adequate exposure is a determinant for therapeutic success; however, considerable inter- and intraindividual variations in drug plasma levels can lead to unfavorable outcomes. While some predictors of isoniazid levels are well-known, others, such as sex, yield controversial results, requiring further investigation to optimize exposure. This study investigates whether the sex of patients influences the dose administered and the concentrations of isoniazid in plasma. Levels of isoniazid were associated with the N-acetyltransferase 2 phenotypes. A total of 76 male and 58 female patients were included. Isoniazid was measured by high-performance liquid chromatography, and N-acetyltransferase 2 phenotypes were assessed using molecular techniques. The results show that the dose administered, expressed in mg/kg, was higher in females, but the plasma levels were similar between both sexes. Among patients, 46.2%, 38.8%, and 15% were slow, intermediate, and fast acetylators, respectively. As expected, isoniazid levels were associated with the acetylation phenotypes, with higher concentrations in the slow acetylators. Thus, sex-related difference in isoniazid levels is due to the body weight of patients, and the optimized dose regimen based on patient weight and acetylator phenotypes can improve the treatment outcomes.