McKenna's Pharmacology for Nursing, 2e

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P A R T 4  Drugs acting on the central and peripheral nervous systems

■■ Anxiety is a feeling of tension, nervousness, apprehension or fear. In the extreme, anxiety may produce physiological manifestations and may interfere with activities of daily life. Anxiolytic drugs, such as the benzodiazepines, depress the CNS to diminish these feelings. ■■ CNS depressants, such as sedatives, block the awareness of and reaction to environmental stimuli. They induce drowsiness, as do hypnotic drugs, which also depress the CNS and inhibit neuronal arousal. ■■ Hypnotics react with GABA-inhibitory sites to depress the CNS. They can cause drowsiness, lethargy and other CNS effects. BARBITURATES USED AS ANXIOLYTIC/ HYPNOTICS The barbiturates were once the sedative/hypnotic drugs of choice. Not only is the likelihood of sedation and other adverse effects greater with these drugs than with newer sedative/hypnotic drugs, but the risk of addiction and dependence is also greater. For these reasons, newer anxiolytic drugs have replaced barbitu- rates in most instances. The only barbiturate used as an anxiolytic/hypnotic in Australia and New Zealand is phenobarbitone. TEACHING FOR P.P. • The drug that has been prescribed for you is called diazepam or Valium . It belongs to a class of drugs called benzodiazepines, which are used to relieve tension and nervousness. Exactly how the drug works is not completely understood, but it does relax muscle spasms, relieve insomnia and promote calm. Common side effects of this drug include: • Dizziness and drowsiness: Avoid driving or performing hazardous or delicate tasks that require concentration if these effects occur. • Nausea, vomiting and weight loss: Small frequent meals may help to relieve nausea. If weight loss occurs, monitor the loss; if the loss is extensive, consult your healthcare provider. Do not take this drug with antacids. • Constipation or diarrhoea: These reactions usually pass with time. If they do not, consult with your healthcare provider for appropriate therapy. • Vision changes, slurred speech, unsteadiness: These effects also subside with time. Take extra care in your activities for the first few days. If these reactions do not go away after 3 or 4 days, consult your healthcare provider. KEY POINTS

Therapeutic actions and indications The barbiturates are general CNS depressants that inhibit neuronal impulse conduction in the ascend- ing RAS, depress the cerebral cortex, alter cerebellar function and depress motor output (see Figure 20.1). Thus, they can cause sedation, hypnosis, anaesthesia and, in extreme cases, coma. In general, barbiturates are indicated for the relief of the signs and symptoms of anxiety and for sedation, insomnia, preanaesthesia and the treatment of seizures (Table 20.2). Parenteral forms, which reach peak levels faster and have a faster onset of action, may be used for the treatment of acute manic reactions and many forms of seizures (see Chapter 23). Pharmacokinetics The barbiturates are absorbed well, reaching peak levels in 20 to 60 minutes. They are metabolised in the liver to varying degrees, depending on the drug, and excreted in the urine. The longer-acting barbiturates tend to be metabolised more slowly and excreted to a greater degree unchanged in the urine. The barbiturates are known to induce liver enzyme systems, increasing the metabolism of the barbiturate broken down by that system, as well as that of any other drug that may be metabolised by that enzyme system. People with hepatic or renal dys- function require lower doses of the drug to avoid toxic effects and should be monitored closely. Barbiturates are lipid soluble; they readily cross the placenta and enter breast milk. • Report any of the following conditions to your healthcare provider: rash, fever, sore throat, insomnia, depression, clumsiness or nervousness. • Tell any doctor, nurse or other healthcare provider involved in your care that you are taking this drug. • Keep this drug and all medications safely away from children or pets. • Avoid the use of over-the-counter medications or herbal therapies while you are taking this drug. If you think that you need one of these products, consult with your healthcare provider about the best choice because many of these products can interfere with your medication. • Avoid alcohol while you are taking this drug. Combining alcohol and a benzodiazepine can cause serious problems. • If you have been taking this drug for a prolonged time, do not stop taking it suddenly. Your body will need time to adjust to the loss of the drug, and the dosage will need to be reduced gradually to prevent serious problems. When discontinuing use of this drug, tell your healthcare provider if the following occurs: trembling, muscle cramps, sweating, irritability, confusion or seizures.