McKenna's Pharmacology for Nursing, 2e

722

P A R T 8  Drugs acting on the cardiovascular system

■■ Nitrates cause blood vessels to relax and dilate. This results in a drop in peripheral resistance and blood pressure and a decrease in venous return to the heart. These actions will decrease myocardial workload and can restore the appropriate balance in the supply– demand ratio in the heart. ■■ Nitrates are available in many forms that vary in time of onset and duration of action. Fast-acting nitrates are used to treat acute anginal attacks. Slower-acting nitrates are used to prevent anginal attacks from occurring. B eta - adrenergic blockers As discussed in Chapter 31, beta-adrenergic blockers are used to block the stimulatory effects of the sympathetic nervous system. The beta-blockers recommended for use in angina include metoprolol ( Betaloc , Minax ) and pro- pranolol ( Inderal ). • Learn to slow down, rest periodically, and schedule your activities to allow your heart to pace its use of energy throughout the day and to help you to maintain your activities without pain. • Glyceryl trinitrate tablets are taken sublingually. Place one tablet under your tongue. Do not swallow until the tablet has dissolved. The tablet should burn slightly or “fizzle” under your tongue; if this does not occur, the tablet is not effective and you should get a fresh supply of tablets. • Ideally, take the glyceryl trinitrate before your chest pain begins. If you know that a certain activity usually causes pain (e.g. eating a big meal, attending a business meeting, engaging in sexual intercourse), take the tablet before undertaking that activity. • Sublingual glyceryl trinitrate is a very unstable compound. Do not buy large quantities at a time because it does not store well. Keep the drug in a dark, dry place and in a dark-coloured glass container, not a plastic bottle, with a tight lid. Leave it in its own bottle. Do not combine it with other drugs. • Some of the following adverse effects may occur: • Dizziness, light-headedness : This often passes as you adjust to the drug. Use great care if you are taking sublingual or transmucosal forms of the drug. Sit or lie down to avoid dizziness or falls. Change position slowly to help decrease the dizziness. • Headache : This is a common problem. Over-the-counter headache remedies often provide no relief for the pain. KEY POINTS

Therapeutic actions and indications The beta-blockers competitively block beta-adrenergic receptors in the heart and juxtaglomerular apparatus, decreasing the influence of the sympathetic nervous system on these tissues. The result is a decrease in the excitability of the heart, a decrease in cardiac output, a decrease in cardiac oxygen consumption and a lowering of blood pressure. They are indicated for the long-term management of angina pectoris caused by atherosclero- sis. These drugs are sometimes used in combination with nitrates to increase exercise tolerance. See Table 46.1 for usual indications for each of these drugs. Beta-blockers are not indicated for the treatment of variant angina because they could cause vasospasm due to blocking of beta-receptor sites. Propranolol and metoprolol can also be used to prevent reinfarction in stable individuals 1 to 4 weeks after an MI. This effect is thought to be caused by the suppression of myocardial oxygen demand for a prolonged period. Pharmacokinetics These drugs are absorbed from the GI tract after oral administration and undergo hepatic metabolism. They Lying down in a cool environment and resting may help alleviate some of the discomfort. • Flushing of the face and neck : This is usually a very minor problem that passes as the drug’s effects pass. • Report any of the following to your healthcare provider: blurred vision, persistent or severe headache, skin rash, more frequent or more severe angina attacks, or fainting. • Sublingual glyceryl trinitrate usually relieves chest pain within 3 to 5 minutes. If pain is not relieved within 5 minutes, take another tablet. If pain continues, take another tablet in 5 minutes. A total of _____ tablets may be used, spaced every 5 minutes. If the pain is not relieved after that time, call your healthcare provider or go to a hospital emergency department as soon as possible. • Tell any doctor, nurse or other healthcare provider involved in your care that you are taking this drug. • Keep this drug, and all medications, out of the reach of children. • Avoid taking over-the-counter medications while you are taking this drug. If you feel that you need one of these, consult with your healthcare provider for the best choice. Many over-the-counter drugs can change the effects of this drug and cause problems. • Avoid alcohol while you are taking this drug because the combination can cause serious problems. • If you are taking this drug for a prolonged period of time, do not stop taking it suddenly. Your body will need time to adjust to the loss of the drug. The dose must be gradually reduced to prevent serious problems.