Most patients with hypertension require combination antihypertensive therapy to control their BP. Monotherapy has been the usual practice followed by step wise titration of the dose of the first drug prescribed to its maximum, before adding another drug or switching to another drug, if the target BP is still not achieved.
A meta-analysis of 42 trials involving 11,000 participants published in Am J Med. 2009;122:290-300 which compared the effects of combining drugs with doubling dose showed that the extra BP reduction from combining drugs from two different classes is approximately 5 times greater than doubling the dose of one drug. Low dose combination therapy also has the advantage of reducing the adverse effects in comparison to maximum dose of monotherapy.
JNC 8 recommends three strategies to physicians: To start one drug, titrate to maximum dose, and then add a second drug (A) or start one drug, then add a second drug before achieving maximum dose of first (B) or begin two drugs at same time, as separate pills or combination pill – Initial combination therapy is recommended if BP is greater than 20/10mm Hg above goal (C) (JAMA. 2014;311:507-20).
The 2017 ACC/AHA guidelines also recommend starting treatment with two first line antihypertensive drugs from different classes when the average systolic BP is 20 mmHg over target and/or the diastolic BP is 10 mm over target in patients with stage 2 hypertension (J Am Coll Cardiol. 2018;71:e127-e248).
Both ACC/AHA guidelines and JNC 8 have recommended against using ACEI and ARB and/or renin inhibitor together in the same patient as it is potentially harmful.
So, if you are not able to reach the desired BP goal or if you need to lower the BP by many units to reach the goal BP, rather than increasing the dose of the initial drug to achieve the target, add another drug of a different class. You may achieve the desired goal BP this way.