<prompt> All are true about guanithidine exceptIt prevents exocytocis of norepinephrineUsed for treatment of erectile dysfunctionSide Effects include diarrhoeaNo CNS related effects are seen with its use  <response>: Refer kK sharma 2195 guanithidine Acts by inhibiting exocytosis of norepinephrine Does not cross blood brain barrier Postural hypotension diarrhoea and erectile dysfunction are the most common adverse side effects 