dextromethorphan and Tuberculosis--Pulmonary

The antitussive effect of several antitussive agents has been objectively evaluated in patients with chronic stable cough due to bronchial carcinoma, pulmonary tuberculosis or chronic obstructive lung disease. The patients received the active antitussive drugs or placebo in a double-blind, randomized crossover design. The preparations were administered at 10 p.m. and 2 a.m. on 7 consecutive nights and no antitussive was given for the following 20 hours. Cough frequency and intensity were recorded from 10 p.m. until 6 a.m. The active medications were noscapine (30 mg), dextromethorphan (20 mg), dihydrocodeine (30 mg) and codeine (20, 30 and 60 mg) at 10 p.m. and 2 a.m. Cough frequency and intensity were objectively assessed with a pressure transducer placed over the trachea and recorded on a chartrecorder. Statistical analysis was performed with analysis of variance and multiple range testing. Noscapine, dextromethorphan, dihydrocodeine and codeine (60 mg) significantly (p less than 0.001) reduced the cough frequency compared to placebo. They also produced a greater reduction of cough intensity than placebo, codeine (20 mg) and codeine (30 mg) (p less than 0.001). The duration of action of low-dose codeine (6 hours) was unsatisfactory. Subjective preference for dextromethorphan indicates a psychotropic central nervous action of this drug not assessed by the measuring device. Noscapine was equally well tolerated but more neutral psychologically.

Topics: Adult; Aged; Antitussive Agents; Bronchitis; Carcinoma, Bronchogenic; Chronic Disease; Clinical Trials as Topic; Codeine; Cough; Dextromethorphan; Double-Blind Method; Humans; Lung Neoplasms; Middle Aged; Noscapine; Tuberculosis, Pulmonary

Accumulating evidence supports the use of higher doses of rifampicin for tuberculosis (TB) treatment. Rifampicin is a potent inducer of metabolic enzymes and drug transporters, resulting in clinically relevant drug interactions. To assess the drug interaction potential of higher doses of rifampicin, we compared the effect of high-dose rifampicin (40 mg/kg daily, RIF40) and standard-dose rifampicin (10 mg/kg daily, RIF10) on the activities of major cytochrome P450 (CYP) enzymes and P-glycoprotein (P-gp). In this open-label, single-arm, two-period, fixed-order phenotyping cocktail study, adult participants with pulmonary TB received RIF10 (days 1-15), followed by RIF40 (days 16-30). A single dose of selective substrates (probe drugs) was administered orally on days 15 and 30: caffeine (CYP1A2), tolbutamide (CYP2C9), omeprazole (CYP2C19), dextromethorphan (CYP2D6), midazolam (CYP3A), and digoxin (P-gp). Intensive pharmacokinetic blood sampling was performed over 24 hours after probe drug intake. In all, 25 participants completed the study. Geometric mean ratios (90% confidence interval) of the total exposure (area under the concentration versus time curve, RIF40 versus RIF10) for each of the probe drugs were as follows: caffeine, 105% (96%-115%); tolbutamide, 80% (74%-86%); omeprazole, 55% (47%-65%); dextromethorphan, 77% (68%-86%); midazolam, 62% (49%-78%), and 117% (105%-130%) for digoxin. In summary, high-dose rifampicin resulted in no additional effect on CYP1A2, mild additional induction of CYP2C9, CYP2C19, CYP2D6, and CYP3A, and marginal inhibition of P-gp. Existing recommendations on managing drug interactions with rifampicin can remain unchanged for the majority of co-administered drugs when using high-dose rifampicin. Clinical Trials registration number NCT04525235.

Topics: Adult; Caffeine; Cytochrome P-450 CYP1A2; Cytochrome P-450 CYP2C19; Cytochrome P-450 CYP2C9; Cytochrome P-450 CYP2D6; Cytochrome P-450 CYP3A; Cytochrome P-450 Enzyme System; Dextromethorphan; Digoxin; Drug Interactions; Humans; Midazolam; Omeprazole; Rifampin; Tolbutamide; Tuberculosis, Pulmonary

Topics: Cough; Dextromethorphan; Morphine Derivatives; Tuberculosis; Tuberculosis, Pulmonary