Dimethyl sulfoxide propylene glycol is a suitable solvent for the delivery of diazepam from osmotic minipumps

The functional integrity of Alzet osmotic minipumps was assessed using two organic solvents (50% (v/v) dimethyl sulfoxide (DMSO)/50% (v/v) propylene glycol (PG) and 100% tetraglycol) which dissolve diazepam, an aqueous insoluble benzodiazepine. Both solvents showed a significant decrease in output rate over time: the decline with tetraglycol was, however, more marked and variable. Further, the DMSO/PG vehicle demonstrated a comparable decline in rate (1.45%) to that of the control vehicles saline and water (1.12%). DMSO/PG is therefore a suitable solvent for the chronic delivery of diazepam from osmotic minipumps.