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The administration of Buspar to a patient taking a monoamine oxidase inhibitor (MAOI) may pose a hazard. There have been reports of the occurrence of elevated blood pressure when Buspar (buspirone hydrochloride) has been added to a regimen including an MAOI. Therefore, it is recommended that Buspar not be used concomitantly with an MAOI.

Because Buspar has no established antipsychotic activity, it should not be employed in lieu of appropriate antipsychotic treatment.

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Buspar is indicated for the management of anxiety disorders or the short-term relief of the symptoms of anxiety. Anxiety or tension associated with the stress of everyday life usually does not require treatment with an anxiolytic.

The efficacy of Buspar has been demonstrated in controlled clinical trials of outpatients whose diagnosis roughly corresponds to Generalized Anxiety Disorder (GAD). Many of the patients enrolled in these studies also had coexisting depressive symptoms and Buspar relieved anxiety in the presence of these coexisting depressive symptoms. The patients evaluated in these studies had experienced symptoms for periods of 1 month to over 1 year prior to the study, with an average symptom duration of 6 months. Generalized Anxiety Disorder (300.02) is described in the American Psychiatric Association’s Diagnostic and Statistical Manual, III1 as follows:

Generalized, persistent anxiety (of at least 1 month continual duration), manifested by symptoms from three of the four following categories:

1. Motor tension: shakiness, jitteriness, jumpiness, trembling, tension, muscle aches, fatigability, inability to relax, eyelid twitch, furrowed brow, strained face, fidgeting, restlessness, easy startle.
2. Autonomic hyperactivity: sweating, heart pounding or racing, cold, clammy hands, dry mouth, dizziness, lightheadedness, paresthesias (tingling in hands or feet), upset stomach, hot or cold spells, frequent urination, diarrhea, discomfort in the pit of the stomach, lump in the throat, flushing, pallor, high resting pulse and respiration rate.
3. Apprehensive expectation: anxiety, worry, fear, rumination, and anticipation of misfortune to self or others.
4. Vigilance and scanning: hyperattentiveness resulting in distractibility, difficulty in concentrating, insomnia, feeling “on edge,” irritability, impatience.

The above symptoms would not be due to another mental disorder, such as a depressive disorder or schizophrenia. However, mild depressive symptoms are common in GAD.

The effectiveness of Buspar in long-term use, that is, for more than 3 to 4 weeks, has not been demonstrated in controlled trials. There is no body of evidence available that systematically addresses the appropriate duration of treatment for GAD. However, in a study of long-term use, 264 patients were treated with Buspar for 1 year without ill effect. Therefore, the physician who elects to use Buspar for extended periods should periodically reassess the usefulness of the drug for the individual patient.

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The mechanism of action of Buspar is unknown. Buspar differs from typical benzodiazepine anxiolytics in that it does not exert anticonvulsant or muscle relaxant effects. It also lacks the prominent sedative effect that is associated with more typical anxiolytics. In vitro preclinical studies have shown that Buspar has a high affinity for serotonin (5-HT1A) receptors. Buspar has no significant affinity for benzodiazepine receptors and does not affect GABA binding in vitro or in vivo when tested in preclinical models.

Buspar has moderate affinity for brain D2-dopamine receptors. Some studies do suggest that Buspar may have indirect effects on other neurotransmitter systems.

BuSpar is rapidly absorbed in man and undergoes extensive first-pass metabolism. In a radiolabeled study, unchanged Buspar in the plasma accounted for only about 1% of the radioactivity in the plasma. Following oral administration, plasma concentrations of unchanged Buspar are very low and variable between subjects. Peak plasma levels of 1 ng/mL to 6 ng/mL have been observed 40 to 90 minutes after single oral doses of 20 mg. The single-dose bioavailability of unchanged Buspar when taken as a tablet is on the average about 90% of an equivalent dose of solution, but there is large variability.

The effects of food upon the bioavailability of BuSpar have been studied in eight subjects. They were given a 20 mg dose with and without food; the area under the plasma concentration-time curve (AUC) and peak plasma concentration (Cmax) of unchanged Buspar increased by 84% and 116%, respectively, but the total amount of Buspar immunoreactive material did not change. This suggests that food may decrease the extent of presystemic clearance of Buspar.

A multiple-dose study conducted in 15 subjects suggests that Buspar has nonlinear pharmacokinetics. Thus, dose increases and repeated dosing may lead to somewhat higher blood levels of unchanged Buspar than would be predicted from results of single-dose studies.

An in vitro protein binding study indicated that approximately 86% of Buspar is bound to plasma proteins. It was also observed that aspirin increased the plasma levels of free Buspar by 23%, while flurazepam decreased the plasma levels of free Buspar by 20%. However, it is not known whether these drugs cause similar effects on plasma levels of free Buspar in vivo, or whether such changes, if they do occur, cause clinically significant differences in treatment outcome. An in vitro study indicated that Buspar did not displace highly protein-bound drugs such as phenytoin, warfarin, and propranolol from plasma protein, and that Buspar may displace digoxin.

Buspar is metabolized primarily by oxidation, which in vitro has been shown to be mediated by cytochrome P450 3A4 (CYP3A4). Several hydroxylated derivatives and a pharmacologically active metabolite, 1-pyrimidinylpiperazine (1-PP), are produced. In animal models predictive of anxiolytic potential, 1-PP has about one quarter of the activity of Buspar, but is present in up to 20-fold greater amounts. However, this is probably not important in humans: blood samples from humans chronically exposed to BuSpar (Buspar hydrochloride) do not exhibit high levels of 1-PP; mean values are approximately 3 ng/mL and the highest human blood level recorded among 108 chronically dosed patients was 17 ng/mL, less than 1/200th of 1-PP levels found in animals given large doses of Buspar without signs of toxicity.

In a single-dose study using 14C-labeled Buspar, 29% to 63% of the dose was excreted in the urine within 24 hours, primarily as metabolites; fecal excretion accounted for 18% to 38% of the dose. The average elimination half-life of unchanged Buspar after single doses of 10 mg to 40 mg is about 2 to 3 hours.

Buspar in Special Populations

Buspar and Age and Gender Effects
After single or multiple doses in adults, no significant differences in Buspar pharmacokinetics (AUC and Cmax) were observed between elderly and younger subjects or between men and women.

Buspar and Hepatic Impairment
After multiple-dose administration of Buspar to patients with hepatic impairment, steady-state AUC of Buspar increased 13-fold compared with healthy subjects.

Buspar and Renal Impairment
After multiple-dose administration of Buspar to renally impaired (Clcr = 10–70 mL/min/1.73 m2) patients, steady-state AUC of Buspar increased 4-fold compared with healthy (Clcr≥80 mL/min/1.73 m2) subjects.

Buspar Race Effects
The effects of race on the pharmacokinetics of Buspar have not been studied.

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BuSpar® (buspirone hydrochloride tablets, USP) is an antianxiety agent that is not chemically or pharmacologically related to the benzodiazepines, barbiturates, or other sedative/anxiolytic drugs.

Buspirone hydrochloride is a white crystalline, water soluble compound with a molecular weight of 422.0. Chemically, buspirone hydrochloride is 8-[4-[4-(2-pyrimidinyl)-1-piperazinyl]butyl]-8-azaspiro[4.5]decane-7,9-dione monohydrochloride.

BuSpar is supplied as tablets for oral administration containing 5 mg, 10 mg, 15 mg, or 30 mg of buspirone hydrochloride, USP (equivalent to 4.6 mg, 9.1 mg, 13.7 mg, and 27.4 mg of buspirone free base, respectively). The 5 mg and 10 mg tablets are scored so they can be bisected. Thus, the 5 mg tablet can also provide a 2.5 mg dose, and the 10 mg tablet can provide a 5 mg dose. The 15 mg and 30 mg tablets are provided in the DIVIDOSE® tablet design. These tablets are scored so they can be either bisected or trisected. Thus, a single 15 mg tablet can provide the following doses: 15 mg (entire tablet), 10 mg (two thirds of a tablet), 7.5 mg (one half of a tablet), or 5 mg (one third of a tablet). A single 30 mg tablet can provide the following doses: 30 mg (entire tablet), 20 mg (two thirds of a tablet), 15 mg (one half of a tablet), or 10 mg (one third of a tablet). BuSpar Tablets contain the following inactive ingredients: colloidal silicon dioxide, lactose, magnesium stearate, microcrystalline cellulose, and sodium starch glycolate. The 30 mg tablet also contains iron oxide.

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Along with its needed effects, a medicine may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.

Check with your doctor immediately if any of the following side effects occur:

Rare
* Chest pain
* confusion
* fast or pounding heartbeat
* fever
* incoordination
* mental depression
* muscle weakness
* numbness, tingling, pain, or weakness in the hands or feet
* skin rash or hives
* sore throat
* stiffness of the arms or legs
* uncontrolled movements of the body

Get emergency help immediately if any of the following symptoms of overdose occur:

Symptoms of overdose
* Dizziness or lightheadedness especially when getting up from a sitting or lying position suddenly
* drowsiness (severe)
* loss of consciousness
* nausea or vomiting
* stomach upset
* very small pupils of the eyes

Some side effects may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects. Check with your health care professional if any of the following side effects continue or are bothersome or if you have any questions about them:

More common
* Restlessness, nervousness, or unusual excitement

Less common or rare
* Blurred vision
* clamminess or sweating
* decreased concentration
* diarrhea
* drowsiness
* dryness of the mouth
* muscle pain, spasms, cramps, or stiffness
* ringing in the ears
* trouble with sleeping, nightmares, or vivid dreams
* unusual tiredness or weakness

Other side effects not listed may also occur in some patients. If you notice any other effects, check with your healthcare professional.

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If you will be using Buspar regularly for a long time, your doctor should check your progress at regular visits to make sure the medicine is working properly and does not cause unwanted effects.

Do not take Buspar if you are also taking a drug with monoamine oxidase (MAO) inhibitor activity (e.g., isocarboxazid [Marplan®], phenelzine [Nardil®], selegiline [Eldepryl®], or tranylcypromine [Parnate®]). If you do, you may develop extremely high blood pressure.

This medicine will add to the effects of alcohol and other CNS depressants (medicines that make you drowsy or less alert). Some examples of CNS depressants are antihistamines or medicine for hay fever, other allergies, or colds; sedatives, tranquilizers, or sleeping medicine; prescription pain medicine or narcotics; barbiturates; medicine for seizures; muscle relaxants; or anesthetics, including some dental anesthetics. Check with your medical doctor or dentist before taking any of the above while you are taking this medicine.

Buspar may cause some people to become dizzy, lightheaded, drowsy, or less alert than they are normally. Make sure you know how you react to this medicine before you drive, use machines, or do anything else that could be dangerous if you are dizzy or are not alert.

Avoid drinking alcoholic beverages while you are using this medicine.

Do not suddenly stop taking this medicine without checking first with your doctor. Your doctor may want you to gradually reduce the amount you are taking before stopping it completely. This is to decrease the chance of having withdrawal symptoms such as increased anxiety; burning or tingling feelings; confusion; dizziness; headache; irritability; nausea; nervousness; muscle cramps; sweating; trouble with sleeping; or unusual tiredness or weakness.

If you think you or someone else may have taken an overdose of Buspar, get emergency help at once. Symptoms of an overdose are dizziness or lightheadedness; severe drowsiness or loss of consciousness; stomach upset, including nausea or vomiting; or very small pupils of the eyes.

Do not take other medicines unless they have been discussed with your doctor. This includes prescription or nonprescription (over-the-counter [OTC]) medicines and herbal or vitamin supplements.

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