A daily dose of 20 mg of
protriptyline can improve daytime arterial blood gas tensions in
chronic obstructive pulmonary disease (
COPD). Its usefulness is limited by
anticholinergic side-effects. This study examined whether a daily dose of 10 mg of
protriptyline improved daytime arterial
oxygen tension (PaO2) and quality of life in patients with stable mild or moderate hypoxaemia caused by
COPD. Twenty six patients were randomized to receive
protriptyline or placebo in a double-blind parallel-group trial for 12 weeks, following a run-in period of 4 weeks, in order to assess the stability of hypoxaemia. Patients with a change in PaO2 of > 0.7 kPa during the run-in were excluded. Spirometry, quality of life and dyspnoea score were measured at randomization and after 12 weeks, whilst arterial blood gas tensions were also measured 2 and 6 weeks after randomization. No improvement in arterial blood gas tensions, spirometry values, dyspnoea score, or quality of life was found in either the
protriptyline or the placebo group. The majority of patients receiving
protriptyline experienced
anticholinergic side-effects, which necessitated the withdrawal of the
drug in one patient. We conclude that there was no evidence that a daily dose of 10 mg of
protriptyline had a significant effect on daytime arterial
oxygen tension in stable mild and moderate hypoxaemia caused by
COPD. Despite the low dose,
anticholinergic side-effects occurred in most patients.