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Oral Antipsychotic Drugs



Antipsychotic drugs are used to treat mental illnesses such as schizophrenia and other psychoses, agitation, severe anxiety, mania and violent or dangerously impulsive behavior. Although antipsychotic drugs don’t cure mental illnesses, they may reduce or eliminate symptoms which involve distortions of reality, including hallucinations, extreme paranoia or fear and disorganized thinking.

Symptoms of psychosis are associated with changes in brain chemicals (called neurotransmitters), including dopamine, serotonin, noradrenaline and acetylcholine. These chemicals regulate numerous aspects of behavior including mood, emotions, control of sleep, wakefulness and feeding. Antipsychotic drugs help to restore the balance of these chemicals, thereby reducing or eliminating the psychotic symptoms. A person should begin to feel better within six weeks of starting antipsychotic medication. However, it may take several months before they feel the full benefits.


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Commonly used oral antipsychotic drugs

All antipsychotic drugs are prescription-only medicines and should only be used under close supervision by healthcare professionals. Most of them are available in oral forms such as tablets and oral solutions.

There are two types of oral antipsychotic drugs :

- Typical (the older type of drugs): examples include Chlorpromazine, Flupenthixol, Haloperidol, Trifluoperazine, Zuclopenthixol; and

- Atypical (the newer type of drugs): examples include Amisulpride, Aripiprazole, Clozapine, Olanzapine, Paliperidone, Quetiapine

While both types of antipsychotic drugs are effective, in general, the atypical antipsychotic drugs have fewer side effects than the typical ones, such as less likely to cause muscle stiffness, restlessness and tardive dyskinesia (uncontrolled movement of the mouth, tongue, face, jaw and sometimes, other parts of the body). However, atypical antipsychotic drugs can be more likely to cause weight gain and increased risk of diabetes and heart disease. Therefore, close monitoring for patient undergoing treatment is required.


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Common side effects of oral antipsychotic drugs

As with all medicines oral antipsychotic drugs can produce side effects in some people. Most side effects go away after a short period of time and often these can be managed successfully.

Common side effects include:

- Drowsiness
- Dizziness when changing positions
- Headache
- Gastro-intestinal disturbances
- Blurred vision
- Dry month
- Constipation
- Change in sexual ability
- Nausea and vomiting

Typical oral antipsychotic drugs are more likely to cause side effects related to physical movement, such as:

- Rigidity
- Persistent muscle spasms
- Tremors
- Restlessness
- Tardive dyskinesia (usually develops in patients on long-term or with high dose therapy)

Atypical antipsychotic drugs are more likely to cause weight gain and changes in a person’s metabolism. This may increase a person’s risk of getting diabetes and high cholesterol.

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Precautions of oral antipsychotic drugs

  • Should be given with caution in patients with cardiovascular disease, Parkinson’s disease, epilepsy, depression, myasthenia gravis, prostatic hypertrophy, susceptibility to angle-closure glaucoma, severe respiratory disease, history of jaundice and blood dyscrasia.

  • Should not be given to patients in comatose states, or with central nervous system depression and phaeochromocytoma.

  • Start with small doses of antipsychotic drugs in patients with severe renal impairment.

  • Avoid abrupt withdrawal after long-term treatment. The sudden stop of antipsychotic drugs can precipitate a range of symptoms, such as nausea, vomiting, diarrhoea, sweating and headache.

  • Some oral antipsychotic drugs can cause drowsiness or impair mental alertness. Do not drive or operate machinery if you feel drowsy or your mental alertness is impaired after taking the drugs.

  • Weight, glucose levels, blood pressure, lipid levels, full blood count, urea and electrolytes and liver function should be monitored regularly by a doctor while taking antipsychotic drugs.

  • Antipsychotic drugs (especially for atypical antipsychotic drugs) may increase the risk of stroke in elderly people with dementia and in patients with pre-existing risk factors for stroke.

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General advice on taking oral antipsychotic drugs

  • Avoid drinking alcohol if you are taking oral antipsychotic drugs as it may increase the risk and severity of the side effects of the medicines.

  • Follow doctor’s advice on the use of your medicine. Do not stop or change the regimen by yourself. You should continue taking the medication even if you are feeling well.

  • Be familiar with the name and dosage of the medicines you are taking. Be cautious of their possible side effects.

  • Avoid extremely hot and humid environments as oral antipsychotic drugs may affect your body’s ability to regulate its temperature and blood pressure

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Communication with your doctor

  • Communicate with your doctor for the best treatment option. Your doctor will prescribe the most appropriate drugs for you after considering your condition and your response to the drugs.

  • Inform your doctor or pharmacist of the medicines you are taking as your medicines may interact with the oral antipsychotic drugs. You should also inform them of any diseases you are suffering as some diseases may warrant special precautions.

  • Inform your doctor that you are pregnant or breast feeding as some of the oral antipsychotic drugs should not be taken by women during that period.
  • Seek advice from your doctor if you suspect you are experiencing side effects from your antipsychotic drugs that are persistent and affecting your daily life.

  • Always ask your doctor before taking any other medicines or health products as they may affect the effect or increase the side effects of your medication.


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Storage of oral antipsychotic drugs

Antipsychotic drugs should be stored in a cool dry place. Unless specified on the label, medicines should not be stored in refrigerators. Furthermore, all drugs should be kept properly in places unreachable by children to prevent accidental ingestion.


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Acknowledgement: The Drug Office would like to thank the Professional Development and Quality Assurance (PD&QA) for their valuable contribution to the preparation of this article.

Drug Office
Department of Health
Dec 2013