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

Buspirone hydrochloride (Buspirone hydrochloride) is a white, crystalline, water soluble compound with a molecular weight of 422.0. Chemically Buspirone hydrochloride (Buspirone hydrochloride) is 8-[4-[4-(2-pyrimidinyl)-1-piperazinyl]-butyl]-8-azaspiro[4,5]decane-7,9- dione monohydrochloride. The molecular formula CHNO • HCl is represented by the following structural formula:

Each tablet for oral administration contains 5 mg, 10 mg, or 15 mg of Buspirone hydrochloride (Buspirone hydrochloride) USP (equivalent to 4.6 mg, 9.1 mg, and 13.7 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 tablet is provided in a special tablet design. This tablet is scored so it 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). In addition, each tablet contains the following inactive ingredients: colloidal silicon dioxide, lactose monohydrate, magnesium stearate, microcrystalline cellulose, and sodium starch glycolate.

The mechanism of action of buspirone is unknown. Buspirone 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 buspirone has a high affinity for serotonin (5-HT) receptors. Buspirone has no significant affinity for benzodiazepine receptors and does not affect GABA binding or when tested in preclinical models.

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

Buspirone is rapidly absorbed in man and undergoes extensive first-pass metabolism. In a radiolabeled study, unchanged buspirone in the plasma accounted for only about 1% of the radioactivity in the plasma. Following oral administration, plasma concentrations of unchanged buspirone are very low and variable between subjects. Peak plasma levels of 1 to 6 ng/mL have been observed 40 to 90 minutes after single oral doses of 20 mg. The single-dose bioavailability of unchanged buspirone 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 buspirone 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 (C) of unchanged buspirone increased by 84% and 116% respectively, but the total amount of buspirone immunoreactive material did not change. This suggests that food may decrease the extent of presystemic clearance of buspirone. (See section.)

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

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

Buspirone is metabolized primarily by oxidation, which has been shown to be mediated by cytochrome P450 3A4 (CYP3A4). (See section.) 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 buspirone, 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 buspirone 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 buspirone without signs of toxicity.

In a single-dose study using C-labeled buspirone, 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 buspirone after single doses of 10 to 40 mg is about 2 to 3 hours.

Buspirone hydrochloride (Buspirone hydrochloride) tablets are 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 buspirone 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 buspirone 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, lll1 as follows:

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

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 buspirone 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 buspirone for 1 year without ill effect. Therefore, the physician who elects to use buspirone for extended periods should periodically reassess the usefulness of the drug for the individual patient.

Buspirone tablets are contraindicated in patients hypersensitive to Buspirone hydrochloride (Buspirone hydrochloride) .

The administration of buspirone to a patient taking a monoamine oxidase inhibitor (MAOI) may pose a hazard.

While formal studies of the interaction of buspirone with alcohol indicate that buspirone does not increase alcohol-induced impairment in motor and mental performance, it is prudent to avoid concomitant use of alcohol and buspirone.

The syndrome of withdrawal from sedative/hypnotic/anxiolytic drugs can appear as any combination of irritability, anxiety, agitation, insomnia, tremor, abdominal cramps, muscle cramps, vomiting, sweating, flu-like symptoms without fever, and occasionally even as seizures.

Amitriptyline:
Diazepam:
Haloperidol:
Trazodone:
Triazolam/Flurazepam:
Other Psychotropics:
Therapeutic levels of aspirin, desipramine, diazepam, flurazepam, ibuprofen, propranolol, thioridazine, and tolbutamide had only a limited effect on the extent of binding of buspirone to plasma proteins (see section).

No evidence of carcinogenic potential was observed in rats during a 24-month study at approximately 133 times the maximum recommended human oral dose; or in mice, during an 18-month study at approximately 167 times the maximum recommended human oral dose.

With or without metabolic activation, buspirone did not induce point mutations in five strains of Salmonella typhimurium (Ames Test) or mouse lymphoma L5178YTK+ cell cultures, nor was DNA damage observed with buspirone in Wi-38 human cells. Chromosomal aberrations or abnormalities did not occur in bone marrow cells of mice given one or five daily doses of buspirone.

In one study of 6632 patients who received buspirone for the treatment of anxiety, 605 patients were ≥ 65 years old and 41 were ≥ 75 years old; the safety and efficacy profiles for these 605 elderly patients (mean age =70.8 years) were similar to those in the younger population (mean age = 43.3 years). Review of spontaneously reported adverse clinical events has not identified differences between elderly and younger patients, but greater sensitivity of some older patients cannot be ruled out.

There were no effects of age on the pharmacokinetics of buspirone (see section).

(See also)

During the premarketing assessment, buspirone was evaluated in over 3500 subjects. This section reports event frequencies for adverse events occurring in approximately 3000 subjects from this group who took multiple doses of buspirone in the dose range for which Buspirone hydrochloride (Buspirone hydrochloride) is being recommended (i.e., the modal daily dose of buspirone fell between 10 and 30 mg for 70% of the patients studied) and for whom safety data were systematically collected. The conditions and duration of exposure to buspirone varied greatly, involving well-controlled studies as well as experience in open and uncontrolled clinical settings. As part of the total experience gained in clinical studies, various adverse events were reported. In the absence of appropriate controls in some of the studies, a causal relationship to buspirone treatment cannot be determined. The list includes all undesirable events reasonably associated with the use of the drug.

The following enumeration by organ system describes events in terms of their relative frequency of reporting in this data base. Events of major clinical importance are also described in the section.

The following definitions of frequency are used: Frequent adverse events are defined as those occurring in at least 1/100 patients. Infrequent adverse events are those occurring in 1/100 to 1/1000 patients, while rare events are those occurring in less than 1/1000 patients.

In human and animal studies, buspirone has shown no potential for abuse or diversion and there is no evidence that it causes tolerance, or either physical or psychological dependence. Human volunteers with a history of recreational drug or alcohol usage were studied in two double-blind clinical investigations. None of the subjects were able to distinguish between buspirone and placebo. By contrast, subjects showed a statistically significant preference for methaqualone and diazepam. Studies in monkeys, mice and rats have indicated that buspirone lacks potential for abuse.

Following chronic administration in the rat, abrupt withdrawal of buspirone did not result in the loss of body weight commonly observed with substances that cause physical dependency.

Although there is no direct evidence that buspirone causes physical dependence or drug-seeking behavior, it is difficult to predict from experiments the extent to which a CNS-active drug will be misused, diverted, and/or abused once marketed. Consequently, physicians should carefully evaluate patients for a history of drug abuse and follow such patients closely, observing them for signs of buspirone misuse or abuse (e.g., development of tolerance, incrementation of dose, drug-seeking behavior).

The recommended initial dose is 15 mg daily (7.5 mg b.i.d.). To achieve an optimal therapeutic response, at intervals of 2 to 3 days the dosage may be increased 5 mg per day, as needed. The maximum daily dosage should not exceed 60 mg per day. In clinical trials allowing dose titration, divided doses of 20 to 30 mg per day were commonly employed.

The bioavailability of buspirone is increased when given with food as compared to the fasted state (see section). Consequently, patients should take buspirone in a consistent manner with regard to the timing of dosing; either always with or always without food.

When buspirone is to be given with a potent inhibitor of CYP3A4 the dosage recommendations described in the section should be followed.

Buspirone HCl Tablets USP are supplied as follows:5 mg tablets: White, oval, biconvex, scored tablets, debossed WATSON and 657, in bottles of 100, 500, and 1000.

10 mg tablets: White, oval, biconvex, scored tablets, debossed WATSON and 658, in bottles of 100, 500, and 1000.

15 mg tablets: White, oval shaped, scored tablets, debossed with the Watson logo and 718, and scoring on both sides so it can be either bisected or trisected, in bottles of 60, 180, 500, and 1000.

Store at 20° - 25°C (68°- 77°F). [See USP controlled room temperature]. Protect from temperatures greater than 30°C (86°F).

Dispense in a tight, light-resistant container as defined in USP/NF.

1. American Psychiatric Association. Ed.: Diagnostic and Statistical Manual of Mental Disorders - lll. American Psychiatric Association, May 1980.

Revised: October 2007

Response to buspirone varies among individuals. Your physician may find it necessary to adjust your dosage to obtain the proper response.

The 15 mg tablet design makes dosage adjustments easy. Each tablet is scored and can be broken accurately to provide any of the following dosages.

If your doctor prescribed the 15 mg tablet:

To break the tablet accurately and easily, hold the tablet between your thumbs and index fingers close to the appropriate tablet score (groove) as shown in the photo. Then, with the tablet score facing you, apply pressure and snap the tablet segments apart (segments breaking incorrectly should not be used).

Manufactured for:Watson Laboratories, Inc.Corona, CA 92880 USA

Manufactured by:Patheon Pharmaceuticals Inc.Cincinnati, OH 45215 USA

Revised: October 2007

Repackaged by:

Rebel Distributors Corp.

Thousand Oaks, CA 91320