Constant-rate infusion of opiates

Constant-rate pump infusion of opiates into peripheral veins is one means of ensuring that opioid delivery is guaranteed. However, there are many problems with this method:

• the drug takes 4-5 half-lives to reach a steady state concentration; hence, toxicity may occur many hours after the start of an infusion
• respiratory depression and obstructive sleep apnoea can occur
• a low patient:nurse ratio is required to monitor treatment correctly

The incidence of complications makes patient-controlled analgesia preferable to constant-rate infusion.