McKenna's Pharmacology for Nursing, 2e

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C H A P T E R 4 6 Antianginal agents

serious respiratory depression when given with general anaesthetics or as an adjunct to anaesthesia. P otassium channel opener There is one other drug group used in the treatment of angina pectoris, namely potassium channel openers of which one, nicorandil ( Ikorel ), is currently available. Therapeutic actions and indications Potassium channel openers promote opening of ATP dependent potassium channels located in vascular smooth muscle, where they cause hyperpolarisation. This effect leads to dilatation of arteries and reduction in afterload. The effect also leads to vascular smooth muscle relaxation, enhancing pooling of blood and reducing preload. Pharmacokinetics Nicorandil is rapidly absorbed after oral administration, mainly through the gastrointestinal system. Peak levels are achieved in 30–60 minutes. The drug and its metab- olites are excreted in urine. Effects during pregnancy and breastfeeding are unknown so the drug is not rec- ommended during these periods. Contraindications and cautions Nicorandil is contraindicated in the presence of allergy to the drug, nicotinamide or nicotinic acid to avoid hypersensitivity reactions and with pregnancy or breast- feeding because of the potential for adverse effects on the fetus or neonate. The drug should not be used in individuals with cardiogenic shock, hypotension or acute myocar- dial infarction, which could be exacerbated by the conduction-slowing effects of the drug. Adverse effects The adverse effects associated with nicorandil are related to their effects on cardiac output and smooth muscle. CNS effects include dizziness, light-headedness, headache and fatigue. GI effects can include nausea, dyspepsia and abdominal pain. Cardiovascular effects include hypotension, tachycardia, palpitations and vaso- dilation. Skin effects include flushing and rash. Clinically important drug–drug interactions Nicorandil has been found to have few drug-drug inter- actions. However, caution should be taken when using the drug concurrently with other drugs that lower blood pressure as this effect may be enhanced . Use of cortico­ steroids with nicorandil has been found to increase risk of gastrointestinal perforation .

Care considerations for people receiving calcium channel blockers and potassium channel openers

Assessment: History and examination

■ ■ Assess for contraindications or cautions: known allergies to any of these drugs to avoid hypersensitivity reactions ; impaired liver or kidney function, which could alter the metabolism and excretion of the drug ; heart block, which could be exacerbated by the conduction depression of these drugs ; and current status of pregnancy or breastfeeding because of the risk of adverse effects to the fetus or breastfeeding baby. ■ ■ Perform a physical assessment to establish baseline status before beginning therapy and during therapy to determine the effectiveness and evaluate for any potential adverse effects. ■ ■ Inspect skin for colour and integrity to identify possible adverse skin reactions. ■ ■ Assess the person’s complaint of pain, including onset, duration, intensity and location, and measures used to relieve the pain. Investigate activity level prior to and after the onset of pain to aid in identifying possible contributing factors to the pain and its progression. ■ ■ Assess cardiopulmonary status closely, including pulse rate, blood pressure, heart rate and rhythm, to determine the effects of therapy and identify any adverse effects. ■ ■ Obtain an ECG as ordered to evaluate heart rate and rhythm. ■ ■ Monitor respirations and auscultate lungs to evaluate changes in cardiac output. ■ ■ Monitor laboratory test results, including liver and renal function tests, to determine the need for possible dose adjustment. rhythm, and cardiac output closely while the drug is being titrated or dose is being changed to ensure early detection of potentially serious adverse effects. ■ ■ Monitor blood pressure very carefully if the person is also taking nitrates because there is an increased risk of hypotensive episodes. ■ ■ If a person is on long-term therapy, periodically monitor blood pressure and cardiac rhythm while using these drugs because of the potential for adverse cardiovascular effects. ■ ■ Provide comfort measures to help the person tolerate drug effects. These include small, frequent Implementation with rationale ■ ■ Monitor the person’s blood pressure, cardiac