Treatment of Complex Regional Pain Syndrome type I; A randomised, single-blind, placebo-controlled study with multiple rounds of S(+)-ketamine infusions.

The treatment of Complex Regional Pain Syndrome type I (CRPS) with S(+)-ketamine showed good pain relief for weeks. However, in most patients, the pain returns to baseline levels. Open label studies suggest a longer duration of pain relief when ketamine is administered more than once. In this randomised, single-blind, placebo-controlled pilot study, we adminster S(+)-ketamine once or twice to test whether pain relief is prolonged with multiple infusions of S(+)-ketamine.

Multiple rounds of S(+)-ketamine infusions will give more profound and prolonged pain relief compared to a single infusion of S(+)-ketamine.

- Baseline measurements before first admission.

- Measurements, on average 3 times a day, during admissions.

- Weekly measurements between and after admissions, until baseline is reached, afterwards on average monthly measurements.

- Follow-up up to 52 weeks from first admission.

Patients are randomised into 3 groups.
Admissions will take place in week 1 and 4 or week 1 and 13 of the study. All patients are admitted twice for 5 days, during which they will receive intravenous S(+)-ketamine or active placebo midazolam, both in an increasing subanesthetic dose based on weight.