Psychosis refers to symptoms such as delusions, hallucinations, disorganized thinking and speech, and bizarre and inappropriate motor behavior that indicate loss of contact with reality. A number of mental disorders cause symptoms of psychosis—see Introduction to Schizophrenia and Related Disorders.
Antipsychotic drugs can be effective in reducing or eliminating symptoms of psychosis. They appear to be most effective in treating hallucinations, delusions, disorganized thinking, and aggression. Although antipsychotic drugs are most commonly prescribed for schizophrenia, they appear to be effective in treating these symptoms whether they result from schizophrenia, mania, dementia, or use of a substance such as amphetamines.
After the immediate symptoms have cleared, depending on the cause of their psychosis, people may need to continue taking antipsychotic drugs to reduce the probability of future episodes.
How Antipsychotic Drugs Work
Antipsychotic drugs work by influencing how information is transmitted between individual brain cells.
The adult brain is made up of more than 10 billion nerve cells called neurons. Each neuron in the brain has a single long fiber called an axon, which transmits information to other neurons (see figure Typical Structure of a Nerve). Like wires connected in a vast telephone switchboard, each neuron makes contact with several thousand other neurons.
Information travels down a cell’s axon as an electrical impulse. When the impulse reaches the end of the axon, a tiny amount of a chemical called a neurotransmitter is released to pass information on to the next cell down the line. A receptor on the receiving cell detects the neurotransmitter, which causes the receiving cell to generate a new impulse.
Types of Antipsychotic Drugs
Antipsychotic drugs are divided into two groups:
First-generation (conventional, older) antipsychotics
Second-generation (newer) antipsychotics
Currently, about 95% of antipsychotics prescribed in the United States are second-generation antipsychotics. Doctors have thought that second-generation antipsychotics were somewhat more effective, but recent evidence casts doubt on this. They may have lower likelihood of some of the more serious adverse effects of first-generation drugs.
Second-generation antipsychotic drugs may relieve positive symptoms (such as hallucinations), negative symptoms (such as lack of emotion), and cognitive impairment (such as reduced mental functioning and attention span). However, doctors are not sure whether they relieve symptoms to a greater extent than the older antipsychotic drugs or whether people are just more likely to take them because they have fewer side effects.
Some conventional and second-generation antipsychotics are available as long-acting injectable preparations that need to be given only once every month or two. These preparations are useful for many people, including those who cannot reliably take oral drugs every day.
Antipsychotics with novel actions are currently being studied and may become available.
Side Effects of Antipsychotic Drugs
Antipsychotic drugs have significant side effects, which can include
Drowsiness
Muscle stiffness
Tremors
Weight gain
Restlessness
Some newer second-generation antipsychotic drugs have fewer side effects. The risk of tardive dyskinesia, muscle stiffness, and tremors is significantly lower with these drugs than with the conventional antipsychotics. However, some of these drugs seem to cause significant weight gain. Some also increase the risk of metabolic syndrome. In this syndrome, fat accumulates in the abdomen, blood levels of triglycerides (a fat) are elevated, levels of high-density cholesterol (HDL, the “good” cholesterol) are low, and blood pressure is high. Also, insulin is less effective (called insulin resistance), increasing the risk of type 2 diabetes.
Tardive dyskinesia
Neuroleptic malignant syndrome is a rare but potentially fatal side effect of antipsychotic drugs. It is characterized by muscle rigidity, fever, high blood pressure, and changes in mental function (such as confusion and lethargy).
