Buspirone is used for the treatment of generalized anxiety disorders and for short term relief of symptoms of anxiety.
Buspirone's mechanism of action is unclear but probably involves actions on such central nervous system chemicals as dopamine, serotonin, acetylcholine, and norepinephrine. These chemicals are called neurotrans-mitters and are involved in the transmission of nervous impulses from cell to cell. Mental well-being is partially dependent on maintaining a balance among different neu-rotransmitters.
Buspirone's actions are different from a common class of sedatives called benzodiazepines. The primary action of benzodiazepines is to reduce anxiety, relax skeletal muscles, and induce sleep. The earliest drugs in this class were chlordiazepoxide (Librium) and diazepam (Valium). Buspirone also acts through a different mechanism than barbiturates such as phenobarbital. Unlike benzodiazepines, buspirone has no anticon-vulsant or muscle-relaxant properties, and unlike benzodiazepines or barbiturates, it does not have strong sedative properties. If insomnia is a component of the patient's anxiety disorder, a sedative/hypnotic drug may be taken along with buspirone at bedtime. Buspirone also diminishes anger and hostility for most people. Unlike benzodiazepines, which may aggravate anger and hostility in some patients, (especially older patients), bus-pirone may help patients with anxiety who also have a history of aggression.
The benefits of buspirone take a long time to become evident. Unlike benzodiazepines, where onset of action and time to maximum benefit are short, patients must take buspirone for three to four weeks before feeling the maximum benefit of the drug. In some cases, four to six weeks of treatment may be required. Patients should be aware of this and continue to take the drug as prescribed even if they think they are not seeing any improvement.
KEY TERMS i n
Acetylcholine—A naturally occurring chemical in e the body that transmits nerve impulses from cell to cell. Generally, it has opposite effects from dopamine and norepinephrine; it causes blood vessels to dilate, lowers blood pressure, and slows the heartbeat. Central nervous system well-being is dependent on a balance among acetylcholine, dopamine, serotonin, and norepinephrine.
Anxiolytic—A preparation or substance given to relieve anxiety; a tranquilizer.
Benzodiazepines—A group of central nervous system depressants used to relieve anxiety or to induce sleep.
Dopamine—A chemical in brain tissue that serves to transmit nerve impulses (is a neurotransmitter) and helps to regulate movement and emotions.
Norepinephrine—A neurotransmitter in the brain that acts to constrict blood vessels and raise blood pressure. It works in combination with serotonin.
Serotonin—A widely distributed neurotransmitter that is found in blood platelets, the lining of the digestive tract, and the brain, and that works in combination with norepinephrine. It causes very powerful contractions of smooth muscle, and is associated with mood, attention, emotions, and sleep. Low levels of serotonin are associated with depression.
Buspirone is available in 5-, 10-, 15-, and 30-mg tablets.
The usual starting dose of buspirone is 10 to 15 mg per day. This total amount is divided into two or three doses during the day. For example, a dose of 5 mg may be given two or three times per day to make a total dose of 10 to 15 mg per day. The dose may be increased in increments of 5 mg daily every two to four days. Most patients will respond to a dose of 15 to 30 mg daily. Patients should not take a total dose of more than 60 mg daily. When patients are receiving certain other drugs (see below) in addition to buspirone, starting doses of buspirone may need to be lowered (for example, 2.5 mg twice daily), and any dosage increases should be done with caution and under close physician supervision. Dosages may need to be reduced in patients with kidney or liver problems.
c Precautions o
'iL Buspirone is less sedating (causes less drowsiness and mental sluggishness) than other anti-anxiety drugs. However, some patients may still experience drowsiness and mental impairment. Because it is impossible to predict which patients may experience sedation with bus-pirone, those starting this drug should not drive or operate dangerous machinery until they know how the drug will affect them.
Patients who have been taking benzodiazepines for a long time should be gradually withdrawn from them while they are being switched over to buspirone. They should also be observed for symptoms of benzodiazepine withdrawal.
Patients with kidney damage should take buspirone with caution in close consultation with their physician. They may require a lower dosage of buspirone to prevent buildup of the drug in the body. Patients with severe kidney disease should not take buspirone. Patients with liver damage should likewise be monitored for a buildup of buspirone and have their doses lowered if necessary.
The most common side effects associated with bus-pirone involve the nervous system. Ten percent of patients may experience dizziness, drowsiness, and headache, and another 5% may experience fatigue, nervousness, insomnia, and light-headedness. Patients may also experience excitement, depression, anger, hostility, confusion, nightmares, or other sleep disorders, lack of coordination, tremor, and numbness of the extremities. Although buspirone is considered non-sedating, some patients will experience drowsiness and lack of mental alertness at higher doses and especially early in therapy. In most patients, these side effects decrease with time.
The following side effects have also been associated with buspirone:
• dry mouth, abdominal distress, gastric distress, and diarrhea, constipation (up to 5% of patients)
• rapid heart rate and palpitations (up to 2% of patients)
• increased or decreased appetite
• non-specific chest pain
• irregular menstrual periods and/or breakthrough bleeding
Dangerously high blood pressure has resulted from the combination of buspirone, and members of another class of antidepressants known as monoamine oxidase (MAO) inhibitors. Because of this, buspirone should never be taken in combination with MAO inhibitors. Patient taking any MAO inhibitors, for example Nardil (phenelzine sulfate) or Parmate (tranylcypromine sulfate), should stop the MAO inhibitor then wait at least 10 days before starting buspirone. The same holds true when discontinuing buspirone and starting an MAO inhibitor.
Certain drugs may inhibit the enzyme system in the liver that breaks down buspirone. Examples of drugs that might inhibit this system are erythromycin, a broad-spectrum antibiotic, itraconazole, an oral antifungal agent, and nefazodone, an antidepressant. When these drugs are combined with buspirone, buspirone concentrations may increase to the point of toxicity (poisoning). These combinations should either be avoided or doses of bus-pirone decreased to compensate for this interaction.
American Society of Health-System Pharmacists. AHFS Drug Information 2002. Bethesda: American Society of Health-System Pharmacists, 2002. DeVane, C. Lindsay, Pharm.D. "Drug Therapy for Anxiety and Insomnia " In Fundamentals of Monitoring Psychoactive Drug Therapy. Baltimore: Williams and Wilkins, 1990.
Jack Raber, Pharm.D.
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