Parenteral diamorphine is 3 times more potent than oral morphine. It is the preferred drug for parenteral use as it is highly soluble in small volumes of diluent.

Diamorphine can be given as required subcutaneously (s.c.) with a duration of action of 4 hours.

Alternatively it can be given as a continuous subcutaneous infusion via a syringe driver.

The total 24 hour subcutaneous continuous infusion diamorphine dose should be one third of the total 24 hour oral morphine dose e.g. a patient on 30mg oral morphine b.d. (60mg in 24 hours divide by 3) would require approximately 20mg s.c. diamorphine over 24hours.

A patient on MST 90mg bd requires conversion to sc diamorphine as he can no longer swallow. What dose would you prescribe?