Beta blockers have been compared with and combined with dihydropyridine calcium channel blockers in controlled clinical trials. The results of the APSIS (Angina Prognosis Study in Stockholm), TIBBS (Total Ischemic Burden Biso- prolol Study), and IMAGE (International Multicenter Angina Exercise) studies showed that a beta blocker was more effective than a calcium channel blocker in control of angina, reduction of cardiovascular events, and need for revascular- ization.786 788 A rationale for combining these agents is a reduction of dihydropyridine-induced tachycardia by beta- blockade. When combined, beta blockers and dihydropyri- dine calcium channel blockers have increased exercise time and shown a trend toward a lower rate of cardiovascular outcomes.788,789 Caution is warranted when a beta blocker is combined with verapamil or diltiazem because of the poten- tial for development of bradycardia, AV block, or excessive fatigue. The combination of a beta blocker with a nitrate could be an additive combination in patients with SIHD. Nitrates increase sympathetic tone, which can lead to reflex tachycardia, which is attenuated by the beta blocker. Beta blockers can increase LV wall tension associated with de- creased heart rate, which is counteracted by the concomitant use of nitroglycerin. Clinical trials have validated this ratio- nale, showing that the combination is more effective in controlling angina than is either monotherapy alone.790,791 Absolute contraindications to beta blockers are severe bradycardia, preexisting high-degree AV block, sick sinus syndrome (without a pacemaker in place), and refractory heart failure. Relative contraindications include bronchospas- tic disease or active PAD (beta blockers without vasodilating properties or selective agents at low doses may be used). Because they can mask symptoms of hypoglycemia, beta blockers should be used with caution in patients with insulin- dependent diabetes mellitus. 