Opioid response to clonidine test as a predictor of effectiveness of antidepressant treatments in chronic headache

In this study we evaluated the opioid response to clonidine administration in headache sufferers with depressive symptoms, to test the hypothesis that such pharmacological tools may help characterize the profile of the different types of chronic headache. The plasma β-endorphin (β-EP) levels were evaluated before and after clonidine administration (0.075 mg IV) in 34 headache patients, 11 suffering from chronic tension headache (CTH) and 23 from migraine with coexisting chronic tension headache (MCTH), prior to starting an antidepressive treatment with amitriptyline or ritanserin. As controls, we examined eight age-matched healthy subjects. Patients as a whole and in the MCTH group, but not the CTH group, showed β-EP levels significantly lower than controls. In all patients and in both CTH and MCTH groups, a blunted response to clonidine administration was observed. Treatments with antidepressive drugs were both effective on pain severity and HRSD score. Moreover, the patients showing the largest increase in plasma β-EP levels following clonidine injection reported a more evident clinical response to the treatments. These findings suggest that the opioid response to the clonidine challenge in chronic headache may well predict the clinical effectiveness of the therapy.