The efficacy and safety of almitrine bismesylate, a new respiratory stimulant, in patients with the hypoxaemic form of chronic respiratory insufficiency caused by chronic bronchitis and emphysema has been assessed. The multicentre trial of 12 weeks duration was double-blind and placebo controlled, with individual and group comparisons. Twenty three patients received almitrine 50 mg b.d. p.o. and 17 took placebo. In the almitrine group a significant increase in PaO2 was achieved (control value 54.4 mm Hg, rising to 59.1 mm Hg after 6 weeks, and to 59.4 mm Hg after 12 weeks). There was also a significant decrease in PaCO2 in the almitrine group after 12 weeks. No correlation was found between the plasma almitrine concentration, PaO2 and PaCO2. Lung function (FVC, FEV1, FEV1/FVC, Raw, TLC, RV, FRC) did not change in either group, but the degree of dyspnoea and performance in the 6 min walking test were significantly improved in the almitrine group. Adverse reactions appeared in 6 out of 23 patients on almitrine bismesylate (headache, urticaria, breathlessness, diarrhoea, chest pain, nausea and vomiting), causing drop out of 4 patients. Thus, almitrine bismesylate can be considered useful in the treatment of patients with chronic respiratory insufficiency.

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