Figure 2 shows the drugs most
frequently prescribed in combination, either as single agents
with 2 separate prescriptions or as components of a single pill
combination, those that have been shown to have the least
additive blood pressure lowering efficacy in clinical trials,
and those studied less well or not at all. Because diuretics
activate the renin-angiotensin-aldosterone system, it is logical
to combine them with classes of drugs that inhibit this
potent vasoconstrictor (angiotensin II) and sodium-retaining
(aldosterone) system.