Simultaneous subcutaneous implantation of two osmotic minipumps connected to a jugular vein catheter in the rat

Subcutaneous osmotic pump implantation connected to a venous catheter is a well-established method for delivering compounds intravenously for an intermediate duration (approximately two weeks). When prolonged release is desired (approximately four weeks) reduced flow rate is needed with a similar pump volume. With a fixed intra-pump compound concentration, reduced flow rate results in unwanted reduced bioavailability of the compound. Prolonged intravenous delivery would therefore need a pump replacement, resulting in increased discomfort and confounding effects on experimental outcome. To overcome this, we describe a method to double the compound infusion rate for four weeks by implanting two low-flow rate osmotic pumps (2.5 mu L/h for 28 days) connected to a jugular vein catheter in a single rat. Rats implanted with a single high-flow rate pump (5 mu L/h for 14 days) served as controls. Double pump-implanted rats displayed similar post-operative weight gain and physical activity indicating similar levels of discomfort when compared with single pump-implanted rats. Double pump-implanted rats had an increased risk of pump-related complications (four delivery failures [double pump] versus one delivery failure [single pump]). Our data show that double pump implantation is a feasible alternative to changing pumps or the use of extracorporeal pump systems connected via a long wire to partly restrained animals.