Quinapril
"I have now tried 11 hypertension medicines.  I found that quinapril gives me a headache, but not as bad as most of the others.  It also makes me dizzy, but not as bad as some of the others.  And like all the ACE inhibitors, it does lower my blood sugar some, but not as bad as lisinopril or any of the the beta blockers. All of the medicines I've tried have contributed to impotence, but unlike the comments of a previous reviewer, I found that quinapril was the least guilty of the lot.  Strangely, since they are both ACE inhibitors, lisinopril is the most guilty."