Chapter 25 Psychopharmacology
Learning outcomes
Introduction
The use of drugs that have a demonstrated ability to relieve the symptoms of psychiatric disorders has become widespread since the mid-1950s (Baldessarini & Tarazi 2001). The pharmacological agents used in current psychiatric practice are the anti-anxiety sedatives, antidepressants, mood-stabilising, neuroleptic and antipsychotic drugs. Collectively, these drugs are referred to as psychotropic medications and are the focus of discussion in this chapter.
Important pharmacological principles
All drugs are prescribed for particular effects or target symptoms that the prescriber hopes to change. Therefore it is important for the nurse to be aware of the symptoms that particular drugs target as well as the symptoms experienced by individual patients. The correct identification of symptoms is a key component of a thorough nursing assessment. Side effects, on the other hand, are the expression of effects for which the drug was not intended. Not all side effects are harmful, but some can be, so the nurse needs a sound working knowledge of this area of practice. Nurses also need to be aware of polypharmacy. Polypharmacy implies the use of multiple psychotropic drugs at the same time. Essentially it is defined as the use of two or more psychotropic drugs, or two or more drugs from the same chemical class, or two or more drugs with the same or similar pharmacological action to treat different conditions (Kingsbury, Yi & Simpson 2001). Although it might be useful at some stage for the management of people with serious psychiatric disorders, polypharmacy is generally not advisable as it can increase the chance of adverse drug side effects and interactions. It can also be extremely problematic with certain groups of vulnerable people, including older people (Shupikai Rinomhota & Marshall 2000).
An understanding of how psychotropic drugs work is important for mental health nurses so that they can better understand the issues surrounding the prescription and administration of these drugs. The neuron is the basic functional unit of the brain and central nervous system (CNS) and all communication in the brain involves neurons communicating across synapses at receptors. Receptors are the targets for the neurotransmitters or chemical messengers necessary for communication between neurons. The neurotransmitters acetylcholine, noradrenaline (norepinephrine), dopamine, serotonin (5HT) and GABA (gamma-aminobutyric acid) are implicated in the development of mental illness. The psychotropic drugs produce their therapeutic action by altering communication among the neurons in the CNS. In particular, they alter the way neurotransmitters work at the synapse by modifying the reuptake of a neurotransmitter into the presynaptic neuron, activating or inhibiting postsynaptic receptors, or inhibiting enzyme activity (Shupikai Rinomhota & Marshall 2000).
Important psychotropic drugs
This section explores the most important groups of psychotropic drugs in current use: the anxiolytics (anti-anxiety), antidepressants, mood-stabilisers and antipsychotics (neuroleptic). These groups of drugs are listed in Table 25.1 with common examples from a local perspective.
Table 25.1 Classification of psychotropic drugs
| type | Drug group | Example |
| Antipsychotic Traditional | ||
| Atypical | ||
| Antidepressant | Tricyclic and related drugs | |
| Selective serotonin reuptake inhibitors and related drugs | ||
| Mono-amine oxidase inhibitors | ||
| Mood stabilising | Lithium | Lithium carbonate |
| Anticonvulsants | ||
| Anti-anxiety | Benzodiazepines | |
| Azapirones Beta-adrenergic blocker | ||
| Sedative-hypnotic | Benzodiazepines | |
| Cyclopyrrolones Imidazopyrimidines |
Anti-anxiety or anxiolytic medications
Anxiety is a common human experience that is a normal reaction to a threat of some kind. It leads to a flight-or-fight response in the individual. Anxiety is also the feature of many mental health problems. When anxiety becomes disabling, anti-anxiety medications may be useful (Shupikai Rinomhota & Marshall 2000). Anti-anxiety drugs can be divided into benzodiazepines and non-benzodiazepines. The benzodiazepines are probably the most commonly prescribed drugs in the world today and are the drug of choice for the short-term treatment of anxiety states.
Indications for use
The benzodiazepines are thought to reduce anxiety because of their potentiation of the inhibitory neurotransmitter GABA, which results in a clinical decrease in the individual’s anxiety by an inhibition of neurotransmission (Shupikai Rinomhota & Marshall 2000). Clinically they are used to treat anxiety, insomnia, alcohol withdrawal, skeletal muscle relaxation, seizure disorders, anxiety associated with medical disease, and psychotic agitation (Ballanger 2000; Battaglia et al 1997; Garza-Trevino, Hollister & Overall 1989). Therefore, although the discussion here is primarily related to the use of these drugs as anti-anxiety agents, they also have a sedative effect and are also often used for that purpose.
Side effects
Side effects from the benzodiazepine drugs (Table 25.2, overleaf) are common, dose related, usually short term, and almost always harmless. They include drowsiness, reduced mental acuity and impaired motor performance. However, other effects such as headache, dizziness, feelings of detachment, nausea, hypotension and restlessness may also be experienced. Therefore the patient should be warned of the risk of accidents and cautioned about driving a car or operating dangerous machinery. These drugs generally do not live up to their reputation of being strongly addictive, especially if they have been used for appropriate purposes, if their use has not been complicated by other factors such as the addition of other medications, and if their withdrawal is planned and gradual. However, if addiction does occur with these medications, the resulting physical depend ence can lead to development of tolerance and onset of a withdrawal syndrome (Box 25.1, overleaf) if they are ceased abruptly.
Table 25.2 Managing benzodiazepine side effects
| Side effect | Intervention |
| Drowsiness | Encourage appropriate activity but warn against engaging in activities such as driving or operating machinery |
| Dizziness | Observe and take steps to prevent falls |
| Feelings of detachment | Encourage socialisation |
| Dependency, rebound insomnia/anxiety | Encourage short-term use; educate to avoid other drugs such as alcohol; plan for withdrawal |
It is also important to remember that older patients are more vulnerable to side effects because the ageing brain is more sensitive to the action of sedatives (Shupikai Rinomhota & Marshall 2000).
Antidepressant drugs
Indications for use
Antidepressant medications are indicated in the treatment of dysthymic disorders, major depression, maintenance treatment of depression and prevention of relapse, and anxiety disorders such as panic disorder and obsessive-compulsive disorder. The drugs elevate mood and alleviate the other symptoms experienced as part of depression. Choice of a particular antidepressant medication will depend on its symptom profile, side effects, comorbid medical conditions, concurrent medications and risk of drug interactions, and the individual’s drug history. If the patient responds to the course of treatment with a particular drug, they should continue taking the drug at the same dosage for up to nine months. If they remain symptom-free during this time then the drug will be gradually withdrawn. Patients whose depressive symptoms return after withdrawal of medication may need long-term maintenance (Treatment Protocol Project 2000).
Side effects
Tricyclic antidepressants
The tricyclic drugs, available on the market for many years now, are clinically similar, so their effects and side effects tend to vary little between individual drugs. They work primarily by serotonin and noradrenaline reuptake inhibition. The blockade of reuptake leads to extra transmitters available for receptor binding. Side effects include sedation, dry mouth, constipation, blurred vision, seizures and urinary retention. They may also cause postural hypotension and serious cardiac problems such as heart block and arrhythmias. Because of their serious side effects these drugs can lead to life-threatening consequences if taken in large quantities, such as in suicide attempts, and if this is suspected, immediate action to support life must be instigated. (Box 25.2 lists signs of overdose.) In the case of severely depressed patients where a potential for suicide is predicted, close supervision is required and when the person is not an inpatient, the dispensing of small, sublethal quantities is recommended (Baldessarini 2001).
Mono-amine oxidase inhibitors
Mono-amine oxidase inhibitors (MAOIs) were the first group of antidepressant drugs discovered. They remain very effective antidepressants; however, due to their potentially serious side effects their use has mostly been replaced by the newer antidepressant drugs. The MAOIs work by inhibiting both types of the enzyme (MAO A and B) that metabolise serotonin and noradrenaline. Patients taking these drugs must avoid noradrenaline agonists, which include its dietary precursor, tyramine. Adverse effects include drowsiness or insomnia, agitation, fatigue, gastrointestinal disturbances, weight gain, hypotension and dizziness, dry mouth and skin, sexual dysfunction, constipation and blurred vision. The major concern with the use of these drugs is their potential to interact with specific foods that contain tyramine, and other amine drugs such as those found in any cough preparation (Box 25.3). Such an interaction can result in excessive and dangerous elevation in blood pressure, known as a hypertensive crisis.
Selective serotonin reuptake inhibitors
The selective serotonin reuptake inhibitor (SSRI) group of antidepressant drugs inhibit the reuptake of serotonin at the presynaptic membrane. This leads to an increased availability of serotonin in the synapse and therefore at the receptors, thereby promoting serotonin transmission. These drugs are as effective as the tricyclic antidepressants but safer, as they cause less serious side effects and have decreased risk of death by overdose. While the actions and effectiveness of these drugs are similar, they are all structurally different from each other, resulting in differences in their side effects. Side effects are similar to those of the tricyclic group except that they do not have the cardiovascular, sedative and anticholinergic side effects. Nausea, diarrhoea, anxiety and restlessness, insomnia, sexual disturbances, loss of appetite, weight loss and headache are the most common. They should not be stopped abruptly; the withdrawal syndrome includes symptoms such as dizziness, paraesthesia, anxiety, sleep disturbance, agitation and tremor. They should not be combined with MAOIs (Shupikai Rinomhota & Marshall 2000).
Interactions
MAOIs
Hypertensive crisis may occur if administered with many other drugs including adrenaline (epinephrine), noradrenaline, reserpine, narcotic analgesics and vasoconstrictors. Clients may also experience hypertensive crisis if tyramine-rich foods are ingested.
Mood stabilisers
Lithium, a naturally occurring salt, is the drug of choice for the treatment of acute mania and for the ongoing maintenance of patients with a history of mania. An Australian, John Cade, discovered its effectiveness as a treatment for mania in 1949. Just how lithium works is not clear, but it is known to mimic the effects of sodium, thereby compromising the ability of neurons to release, activate or respond to neurotransmitters. It does appear to reduce the sodium content of the brain, and increase central serotonin synthesis and noradrenaline reuptake (Shupikai Rinomhota & Marshall 2000). A number of other drugs have also been used successfully, either alone or in combination with lithium, to control the symptoms of mania. The antidepressants and a number of anticonvulsant drugs have also been used very successfully to reduce mania.
Indications for use
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