Inclusion Criteria:  Meeting the new International Association for the Study of Pain (IASP) diagnostic criteria for CRPS ("the Budapest Criteria) (Harden et al., 2010) or having met the new IASP diagnostic criteria of CRPS ("CRPS with Remission of Some features") (Goebel et al., 2021). Willing and capable to participate in the study. CRPS in one upper extremity and/or CRPS in one lower extremity Treatment in an elective setting. Adequate comprehension of the Dutch language Age ≥ 18 years  Exclusion Criteria:  Severe liver disease Psychiatric (schizophrenia, psychosis, delirium, manic depression) Active substance abuse Intoxication with alcohol or other substances Poorly controlled hypertension Unstable angina High-risk coronary vascular disease Heart failure Elevated intracranial pressure Elevated intraocular pressure Thyrotoxicosis Pregnancy Combination with derivates of xanthines (theophylline) or ergometrine