Clonidine and sleep apnea syndrome interaction: antagonism with yohimbine.

A patient with sleep apnea syndrome, concurrently taking clonidine as an antihypertensive, presented with severe respiratory acidosis, hypotension, and associated central nervous system depression. Acidosis was improved by mechanical ventilation, and central nervous system (CNS) depression and hypotension were reversed with yohimbine. Clonidine may have an additive CNS depressive effect in sleep apnea syndrome and should be used with caution in such patients. Yohimbine's sympathetic-enhancing effects may be useful in clonidine toxic states.