Systemic absorption of nebulized morphine compared with oral morphine in healthy subjects

The inhalation of nebulized morphine has been advocated to treat dyspnoea and pain in patients with cancer. We have compared plasma morphine concentrations in healthy volunteers after nebulized (50 mg in 4 ml saline), oral (10 mg solution) and intravenous (5 mg) morphine sulphate. Bioavailability was estimated by dividing the morphine concentration AUC/dose by that obtained after intravenous morphine. Peak plasma morphine concentrations were achieved more rapidly after nebulized than oral morphine, occurring within 10 min in all subjects. The systemic bioavailabilities of morphine (mean+/-s.d.) were 5+/-3% and 24+/-13% for the nebulized and oral routes respectively. Nebulization is a rapid but inefficient method of administering morphine. It may provide more rapid pain relief compared with oral morphine but clinical studies are needed to confirm this.