McKenna's Pharmacology for Nursing, 2e

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

Contraindications and cautions Antipsychotic drugs are contraindicated in the presence of underlying diseases that could be exacerbated by the dopamine-blocking effects of these drugs. They are also contraindicated in the following conditions, which can be exacerbated by the drugs : central nervous system (CNS) depression, circulatory collapse, Parkinson’s disease, coronary disease, severe hypotension, bone marrow suppression and blood dyscrasias. Prolongation of the QT c interval is a contraindication to the use of ziprasidone which can further prolong the QT c interval, leading to increased risk of serious cardiac arrhythmias. Antipsychotics are contraindicated for use in elderly people with dementia because this use is associated with an increased risk of cardiovascular events and death. In 2005, the US Food and Drug Administration (FDA) issued a public health advisory regarding the use of antipsychotics after post-marketing studies showed that when these drugs were used to control behavioural symptoms of dementia in older adults, the people being treated experienced increased cardiovascular events and death. None of these drugs is approved for this use, but it was common practice in many settings to use them, off-label, to establish behavioural control of people with dementia. Antipsychotics now have a black-box warning on the prescribing information outlining this safety information and contraindication. Caution should be used in the presence of medical conditions that could be exacerbated by the anticholin- ergic effects of the drugs , such as glaucoma, peptic ulcer and urinary or intestinal obstruction. In addition, care should be taken in people with seizure disorders because the threshold for seizures could be lowered ; in people with thyrotoxicosis because of the possibility of severe neurosensitivity ; and in people with active alcoholism because of potentiation of the CNS depression. Other situations that warrant caution include mye- lography within the last 24 hours or scheduled within the next 48 hours because severe neuron reaction to the dye used in these tests can occur, and pregnancy or breastfeeding because of the potential of adverse effects on the fetus or neonate . Antipsychotic agents should be used only if the benefit to the mother clearly outweighs the potential risk to the fetus or baby. Because children are more apt to develop dystonia from the drugs, which could confuse the diagnosis of Reye’s syndrome , caution should be used with children younger than 12 years of age who have a CNS infection or chickenpox. The use of antipsychotics may result in bone marrow suppression, leading to blood dyscrasias , so care should be taken with people who are immunosuppressed and those who have cancer.

Cultural considerations

BOX 22.3

Antipsychotic drugs The ways in which people in certain cultural groups respond to antipsychotic drugs—either physiologically or emotionally—may vary.Therefore, when a pharmacological regimen is incorporated into overall care, healthcare providers must consider and respect an individual’s cultural beliefs and needs. • African Americans respond more rapidly to antipsychotic medications and have a greater risk for development of disfiguring adverse effects, such as tardive dyskinesia. Consequently, these people should be started off at the lowest possible dose and monitored closely. African Americans also display a higher red blood cell plasma lithium ratio than Caucasians do and they report more adverse effects from lithium therapy.These people should be monitored closely because they have a higher potential for lithium toxicity at standard therapeutic ranges. • People in Asian countries, such as India,Turkey, Malaysia, China, Japan and Indonesia, receive lower doses of neuroleptics and lithium to achieve the same therapeutic response as seen in people in Australia and New Zealand.This may be related to these individuals’ lower body mass as well as metabolic differences. • Arab people metabolise antipsychotic medications more slowly than Asian people do and may require lower doses to achieve the same therapeutic effects as in Caucasians. • Individuals in some cultures use herbs and other folk remedies, and the use of herbs may interfere with the metabolism of Western medications.The nurse or midwife should carefully assess for herbal use and be aware of potential interactions. In prescribing for the elderly, the balance between risks and benefit should be considered before prescribing antipsychotic drugs. In elderly adults with dementia, antipsychotic drugs are associated with a small increased risk of mortality and an increased risk of stroke or transient ischaemic attack. Furthermore, elderly adults are particularly susceptible to postural hypotension and to hyperthermia and hypothermia in hot or cold weather. It is recommended that antipsychotic drugs should not be used in elderly adults to treat mild psychotic symptoms. Initial doses of antipsychotic drugs in the elderly should be reduced (to half the adult dose or less), taking into account factors such as the person’s weight, co-morbidity and concomitant medication. Treatment should be reviewed regularly. ■■ BOX 22.4  Antipsychotic drugs and the older person