In a multilamellar liposome, a pharmaceutical agent is encapsulated in the liposome in the absence of a partition enhancing buffer. Preferably, the pharmaceutical agent is prostaglandin E1 (PGE1). The pharmaceutical agent may be administered to a mammal in an amount effective to treat vascular disease. The release of the pharmaceutical agent from the multilamellar liposome may be regulated by proper selection of liposome size, dosage of the pharmaceutical agent, lipid to pharmaceutical agent weight ratio, and rate of infusion of the pharmaceutical agent.
