Antidepressants - Psychopharmacology - Lehne\'s Pharmacology for Nursing Care PDF

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Psychopharmacology...

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The principal symptoms of major depression are depressed mood and loss of pleasure or interest in one’s usual activities and pastimes. Patients with mild depression can be treated equally well with antidepressant drugs or psychotherapy. Patients with severe depression respond better to a combination of drugs plus psychotherapy than to either intervention alone. Patients with depression often think about or attempt suicide. During treatment with antidepressants, especially initially, the risk of suicide may increase. To reduce the risk of suicide, patients should be followed closely by family members, caregivers, and the prescriber. Suicide risk is greatest in children and young adults. All antidepressants appear equally effective. Differences relate primarily to side effects, drug interactions, and cost. Therapeutic responses to antidepressants develop slowly. Initial responses develop in 1 to 3 weeks. Maximal responses may not be seen until 12 weeks. Antidepressant therapy should continue for 4 to 9 months after symptoms resolve. SSRIs block reuptake of serotonin, and thereby intensify transmission at serotonergic synapses. Over time, this induces adaptive cellular responses that are ultimately responsible for relieving depression. SSRIs have two major advantages over TCAs: they cause fewer side effects and are safer when taken in overdose. Most SSRIs have stimulant properties, and hence can cause insomnia and agitation. This contrasts with TCAs, which cause sedation. Like most other antidepressants, SSRIs can cause weight gain. Sexual dysfunction (e.g., impotence, anorgasmia) is more common with SSRIs than with most other antidepressants. SSRIs can cause serotonin syndrome, especially when combined with MAOIs. Symptoms include agitation, confusion, hallucinations, hyperreflexia, tremor, and fever. Combined use of SSRIs and MAOIs is contraindicated, and combined use with other serotonergic drugs (see Table 32.4) should be done with extreme caution, if at all. SNRIs block reuptake of serotonin and norepinephrine. Effects are similar to those of the SSRIs. The most common side effects of SNRIs include nausea, insomnia, and hypertension. SNRIs can also contribute to sexual dysfunction. SNRIs, like SSRIs, can cause serotonin syndrome. TCAs block reuptake of NE and 5-HT and thereby intensify transmission at noradrenergic and serotonergic synapses.

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Over time, this induces adaptive cellular responses that are ultimately responsible for relieving depression. The most common adverse effects of TCAs are sedation, orthostatic hypotension, and anticholinergic effects (e.g., dry mouth, constipation). The most serious adverse effect of TCAs is cardiotoxicity, which can be lethal if an overdose is taken. TCAs can cause a hypertensive crisis if combined with an MAOI. Accordingly, the combination is generally avoided. TCAs intensify responses to direct-acting sympathomimetics (e.g., epinephrine) and diminish responses to indirect-acting sympathomimetics (e.g., amphetamine). MAOIs increase neuronal stores of NE and 5-HT, and thereby intensify transmission at noradrenergic and serotonergic synapses. Over time, this induces adaptive cellular responses that are ultimately responsible for relieving depression. MAOIs are as effective as SSRIs and TCAs, but are potentially more hazardous. MAOIs are first-choice drugs only for patients with atypical depression. Like SSRIs and SNRIs (and unlike TCAs), MAOIs cause direct CNS stimulation. Like TCAs (and unlike SSRIs or SNRIs), MAOIs cause orthostatic hypotension. Patients taking MAOIs must not eat tyramine-rich foods because hypertensive crisis can result. Hypertensive crisis can be treated with an IV vasodilator (e.g., sodium nitroprusside, labetalol, phentolamine). MAOIs must not be combined with indirect-acting sympathomimetics (e.g., amphetamine, cocaine) because hypertensive crisis can result. MAOIs must not be combined with SSRIs, SNRIs, or other serotonergic drugs because serotonin syndrome could result. ECT relieves depression faster than antidepressant drugs, and often helps when antidepressants have failed. ECT as practiced today is safer and less traumatic than in the past, owing to adjunctive use of (1) a short-acting IV anesthetic (e.g., propofol, etomidate) to produce unconsciousness and (2) a short-acting muscle relaxant (succinylcholine) to prevent convulsions.

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