Calcium channel blockers What are calcium channel blockers? This is a family of medicines rather than one in particular. Diltiazem and nifedipine are the most commonly prescribed in PH. These are a group of medicines used for a range of different uses, including angina and high blood pressure. Some CCBs are also prescribed for Raynauds Phenomenon. CCBs are vasodilators, hence they open up blood vessels. Unlike other PH treatments, these work on large blood vessels near the heart and small vessels in the fingers and toes as well as those in the lungs. CCBs will only benefit patients with idiopathic pulmonary arterial hypertension (PAH), and more specifically those who show a positive response to the vasodilator challenge during the right heart catheter (RHC). The RHC is the test used to diagnose (PAH) and measure the pressures in the chambers of the heart. The vasodilator challenge is part of the procedure where the doctors are looking for the high pressures to come back towards normal after a dose of a vasodilating medicine. If this is the case, patients would be treated with CCBs as first line therapy rather than one of the other targeted PH therapies. Around half of the people who respond to the vasodilator challenge can be treated with CCBs long term. How to take calcium channel blockers Nifedipine and diltiazem are the most commonly used CCBs for PAH but may be prescribed in far higher doses (nifedipine up to 90mg daily, diltiazem up to 720mg daily) than for other uses such as angina. Both these treatments can be taken twice daily, but are generally prescribed as long-acting tablets or capsules and as such only needed once daily. In order to reach the high doses and manage side effects, patients are up-titrated slowly. Contra-indications Do not take CCBs if you: • Have had an allergic reaction to the CCB in the past. • Are trying to get pregnant, are already pregnant or you are breastfeeding. • Have liver or kidney disease. • Have heart failure or you’ve recently had a heart attack. Side effects of calcium channel blockers CCBs are usually well tolerated, but especially because high doses are needed, patients may be at greater risks of problems. Common problems are headache, dizziness, flushing, a pounding heartbeat and swollen ankles. That said, these are often features of PH, so always check with your PH centre if you are in any doubt. Other useful information These are the only form of treatment for PH that GPs are allowed to supply. All other medicines for PH must be prescribed by the PH centres. If you forget to take a dose of any CCBs, take it as soon as you remember – never take a double dose to make up for the missed one.