11th May 2025

Targeted Medical Therapy

Targeted medical therapy is commenced by specialist PH centres. Their aim is to improve exercise capacity and symptoms, haemodynamic parameters and patient quality of life. It is indicated in patients with PAH class II and above who have not responded to general supportive measures. 

Some patients with IPAH may benefit from calcium channel blockade. To isolate this subgroup, patients with IPAH without right sided cardiac failure undergo vasodilator testing to identify those whose pulmonary arterial pressures fall following the administration of vasodilators. The minority of patients (10-15%) have a positive response to vasodilators (fall in mean pulmonary artery pressure of >20% with an increased or unchanged cardiac output during acute challenge) and can commence treatment on CCB’s. CCB’s are aimed at reducing pulmonary vascular resistance. Choice of CCB is dependent on the patient’s baseline heart rate. If heart rate is less than 100 beats per minute nifedipine or amlodipine would be first line, however if the patient’s heart rate is greater than 100 beats per minutes then diltiazem would be the preferred drug for its negatively chronotropic effect. 

Most patients with PAH have a negative response to vasodilator testing. These patients should be considered for alternative targeted medical therapy, which consists of 4 drug classes shown in Table 3 below.

Table 3: PAH targeted medical therapy drug classes

Treatment decision is dependent on risk stratification of patients into either low, intermediate or high risk. This risk stratification is based on clinical judgement and the following criteria defined in Table 4.

Table 4: PH risk stratification criteria

Low or intermediate risk patients can be commenced on an oral agent from one of the above classes or on multiple in the form of oral combination therapy. If the patient is unresponsive to oral combination therapy, they are then considered for parenteral prostanoids, such as epoprostenol, with the option of adding an endothelin receptor antagonist or phosphodiesterase-5 inhibitor or soluble guanylate cyclase stimulator.

Patients within the high-risk group should be immediately started on an intravenous epoprostenol, which can prolong survival. If treatment goals are not achieved, combination therapy with an endothelin receptor antagonist or phosphodiesterase-5 inhibitor is indicated.