Oral diamorphine: lack of effect on dyspnoea and exercise tolerance in the "pink puffer" syndrome.

The aim of this study was to assess the effects of diamorphine on breathlessness and exercise tolerance in patients with severe chronic airflow obstruction and normal arterial carbon dioxide tension (PCO2) levels ("pink puffer" syndrome). In this double-blind, cross-over, randomized study we examined both acute and chronic effects of single and multiple doses of oral diamorphine in 14 "pink puffer" patients. Their mean resting forced expiratory volume in one second (FEV1) was 36% predicted normal, mean arterial oxygen tension (PaO2) was 9.2 kPa and mean PaCO2 was 5.2 kPa. Ten patients took either diamorphine 2.5 or 5 mg or placebo elixir 6 hourly for 2 weeks, recording on a diary card dyspnoea, sleepiness and well-being on a visual analogue scale (VAS). The final treatment was given 30 min before measuring spirometry, arterial blood gases, plasma morphine levels, 6 min walking distances, time walked on treadmill and self-assessment of dyspnoea on a VAS scale after exercise. On two further days, eight patients took two doses, 4 h apart, of either diamorphine 7.5 mg or placebo elixir. Spirometry, 6 min walking distance with a VAS score for dyspnoea were measured before and at 1 h after each dose. Morphine levels and blood gases were also measured. Whether given in single or repeated doses, oral diamorphine had no significant effect on exercise tolerance and breathlessness when compared with placebo. Diamorphine 2.5-7.5 mg produced neither sleepiness nor a deterioration in blood gases. However, plasma levels associated with analgesic efficacy were not achieved with these doses. Thus, as given in this study, oral diamorphine is unlikely to have therapeutic potential in the treatment of dyspnoea in the "pink puffer" syndrome.