Hypertensive crisis possibly due to drug interaction

This report describes a case of possible drug interaction in a patient taking chlorpromazine and guanethidine who experienced a hypertensive crisis following initiation of doxepin therapy. (We have been unable to find a report of a similar interaction at the doses described.) It is advised that physicians exercise caution when contemplating concomitant use of doxepin and guanethidine, even in usually recommended doses.