McKenna's Pharmacology for Nursing, 2e

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

■■ The SSRIs prevent the reuptake of serotonin into the presynaptic nerve, leading to an accumulation of these biogenic amines in the synaptic cleft. This accumulation causes increased stimulation of the postsynaptic nerve and may be responsible for the antidepressant effects of these drugs. ■■ The SSRIs are not associated with many of the CNS, CV and anticholinergic effects of other antidepressants. OTHER ANTIDEPRESSANTS Some other effective antidepressants do not fit into any of the three groups that have been discussed in this chapter. These drugs have varying effects on noradrena­ line, 5HT and dopamine. Although it is not known how their actions are related to clinical efficacy, these agents may be most effective in treating depression in people who do not respond to other antidepressants. They may even be used before MAO inhibitors or TCAs, which have many more adverse effects. As with the other anti­ depressants, these drugs have a black box warning to be alert for the possibility of increased suicidality, espe­ cially in children and adolescents, whenever the drugs are used. Other antidepressants include the following (see Table 21.5 for usual indications): • Agomelatine ( Valdoxan ) (not available in New Zealand) is a melatonergic antidepressant used in the treatment of major depressive disorder. The drug is Provide support and reassurance to help D.J. deal with drug effects (4-week delay in full effectiveness). Provide teaching regarding drug dosage, adverse effect conditions to report and the need to use barrier contraceptives. Evaluation Evaluate drug effects: relief of signs and symptoms of depression. Monitor for adverse effects: sedation, dizziness, insomnia; respiratory dysfunction; GI upset; GU problems; rash. Monitor for drug–drug interactions. Evaluate effectiveness of teaching program. Evaluate effectiveness of comfort and safety measures. TEACHING FOR D.J. • The drug that has been prescribed is called a selective serotonin reuptake inhibitor or SSRI. SSRIs change the concentration of serotonin in specific areas of the brain. An increase in serotonin level is believed to relieve depression. • The drug should be taken once a day in the morning. If your dosage has been increased or if you are having stomach upset, the dose may be divided. KEY POINTS

metabolised in the liver and excreted through urine. A substantial increase in selegiline bioavailability (up to threefold) occurs when selegiline is administered with food high in fat. The drug does cross the placenta and enters breast milk, so it should only be used during pregnancy and breastfeeding if the benefit outweighs the potential risk to the neonate. This drug is associated with CNS effects, as well as GI effects including nausea, dry mouth and abdominal pain. • Bupropion ( Prexaton ) weakly blocks the reuptake of noradrenaline, 5HT and dopamine. At lower doses, this drug is effective in smoking cessation. It is well absorbed from the GI tract, metabolised in the liver and excreted in the urine. Zyban tablets should be swallowed whole and not crushed or chewed as this may lead to an increased risk of adverse effects including seizures. There are no adequate studies done in pregnancy, and the drug should be used during pregnancy only if the benefits to the mother clearly outweigh the potential risks to the fetus. Bupropion does enter breast milk and should not be used by breastfeeding women. The drug is available in a sustained-release formulation which some people find to be more convenient. • Desvenlafaxine ( Pristiq ) (not available in New Zealand) is the newest of the SSRIs. It blocks the reuptake of noradrenaline and 5HT. It is readily absorbed from the GI tract, reaching peak levels in 7.5 hours. It is metabolised in the liver and excreted through urine within about 72 hours. It passes into breast milk and should not be used by breastfeeding contraceptives is recommended while you are taking this drug. If you think that you are pregnant or would like to become pregnant, consult with your healthcare provider. • It may take as long as 4 weeks before you feel the full effects of this drug. Continue to take the drug every day during that time so that the concentration of the drug in your body eventually reaches effective levels. • Common side effects of SSRIs include the following: • Dizziness, drowsiness, nervousness and insomnia: If these effects occur, avoid driving or performing hazardous or delicate tasks that require concentration. • Nausea, vomiting and weight loss: Small frequent meals may help. Monitor your weight loss; if it becomes excessive, consult your healthcare provider. • Sexual dysfunction and flu-like symptoms: These effects may be temporary. Consult with your healthcare provider if these conditions become bothersome. • Report any of the following conditions to your healthcare provider: rashmania, seizures and severe weight loss . • Tell your doctors, nurses and other healthcare providers that you are taking this drug. Keep this drug and all medications out of the reach of children and pets. Do not take this drug during pregnancy because severe fetal abnormalities could occur. The use of barrier