The aim of this pilot study for the NorCAPITAL trial is to investigate the feasibility and safety of the drug clonidine in adolescent chronic fatigue syndrome (CFS). Specifically, the investigators wanted to assess appropriate dosage in relation to a) plasma concentration levels of clonidine, b) orthostatic cardiovascular responses (the pulse and blood pressure responses when rising up), and c) reports of possible adverse effects.

A possible beneficial effect of clonidine in adolescent CFS will be investigated in NorCAPITAL, which is a randomized, placebo-controlled, double blind trial.

Inclusion Criteria:

• Persisting or constantly relapsing fatigue lasting 3 months or more
• Functional disability resulting from fatigue to a degree that prevent normal school attendance
• Age between 12 and 19 years

Exclusion Criteria:

• Another disease process or current demanding life event that might explain the fatigue
• Another chronic disease
• Permanent use of drugs
• Permanently bed-ridden
• Positive pregnancy test
• Supine systolic blood pressure (SBP) < 85 mm Hg
• Fall in SPB upon standing > 30 mm Hg
• Supine HR < 50 beats/min
• Abnormal ECG