Tuberculosis (TB) is an infectious disease caused by Mycobacterium tuberculosis,
generally affecting the lungs and leading to death. The Ministry of Health
recommends for the treatment of new cases of pulmonary tuberculosis the
association of chemotherapy drugs administered in two phases: the intensive one,
which lasts two months, and Rifampicin (600 mg), Isoniazid (300 mg), Pyrazinamide
(1600 mg) and Ethambutol (1100 mg) (2RHZE) and maintenance, for four months,
when Rifampicin (600 mg) and Isoniazid (300 mg) (4RH) are administered. The full
dose of medication is indicated for patients over 50 kg. A determinant of therapeutic
success is the exposure of the bacillus for a certain period of time to effective
concentrations of chemotherapeutic agents, that is, above the minimum inhibitory
concentration (MIC), which in this case of rifampicin ranges from 0.05 µg / ml to 0.5
µg / ml, in addition, studies have shown that maximum plasma drug concentrations
above 8.0 µg / ml are associated with a high rate of therapeutic success. However,
there is a high intra and interindividual variation in the plasma concentrations of
rifampicin in the usual therapeutic doses, caused by factors related to the patient
and the drug dispensed, which can interfere with exposure, as well as the
administered doses and anthropometric measurements of the patients. The aim of
the present study was to investigate the factors that influence plasma concentration
when exposed to rifampicin in the treatment of pulmonary tuberculosis in a Basic
Health Unit in Belém / Pa. A cross-sectional and observational study was carried out
of 70 cases of subjects of both sexes, with clinical, radiological and laboratory
diagnosis of tuberculosis by M. tuberculosis, distributed in the intensive and
maintenance phases of treatment. Plasma concentrations of rifampicin were
determined, as well as anthropometric measurements of weight, height, fat
percentage and abdominal circumference of each individual and the application of
the Morisky-Green Test to assess adherence. Thus, the sample included in the study
was composed mainly of adult men with low education and income. Plasma
concentrations of rifampicin were above the minimum inhibitory concentration of M.
tuberculosis indicating adequate exposure to the drug, which can be measured by
the high proportion of patients who had smear conversion at the end of the first
month of treatment. Sex was not a predictor of variation in plasma rifampin
concentrations. The treatment phase was considered to be a predictor of variation
in plasma drug concentrations. The concentrations of rifampicin were not associated
with the Body Mass Index, waist circumference and fat percentage both in patients
in the intensive phase and in those in maintenance of treatment. Adherence to
tuberculosis treatment was 88.1% and 82.14% in patients in the intensive and
maintenance phases, respectively. Plasma concentrations of rifampicin were not
associated with the Morisky-Green Test.
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