Prescription drugs info

Buspar should not be used with antidepressant drugs known as monoamine oxidase (MAO) inhibitors.

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Buspar is used in the treatment of anxiety disorders and for short-term relief of the symptoms of anxiety.

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BuSpar® (buspirone hydrochloride tablets, USP) Tablets, 5 mg and 10 mg (white, ovoid-rectangular with score, MJ logo, strength and the name BuSpar embossed) are available in bottles of 100.

5 mg tablets
NDC 0087-0818-41     Bottles of 100

10 mg tablets
NDC 0087-0819-41     Bottles of 100

Tablets, 15 mg white, in the DIVIDOSE® tablet design imprinted with the MJ logo, are available in bottles of 60 and 180. Tablets, 30 mg pink, in the DIVIDOSE® tablet design imprinted with the MJ logo, are available in bottles of 60. The 15 mg and 30 mg tablets are scored so that they can be either bisected or trisected. The 15 mg tablet has ID number 822 on one side and on the reverse side, the number 5 on each trisect segment. The 30 mg tablet has ID number 824 on one side and on the reverse side, the number 10 on each trisect segment.

15 mg tablets
NDC 0087-0822-32     Bottles of 60
NDC 0087-0822-33     Bottles of 180

30 mg tablets
NDC 0087-0824-81     Bottles of 60

US Patent No. 5,015,646

Store Buspar at 25° C (77° F); excursions permitted between 15° C to 30° C (59° F to 86° F) [see USP controlled room temperature]. Dispense in a tight, light-resistant container (USP).

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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 mg to 30 mg per day were commonly employed.

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

When Buspar is to be given with a potent inhibitor of CYP3A4, the dosage recommendations described in the PRECAUTIONS: Drug Interactions section should be followed.

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Buspar overdosage Signs and Symptoms
In clinical pharmacology trials, doses as high as 375 mg/day were administered to healthy male volunteers. As this dose was approached, the following symptoms were observed: nausea, vomiting, dizziness, drowsiness, miosis, and gastric distress. A few cases of overdosage have been reported, with complete recovery as the usual outcome. No deaths have been reported following overdosage with BuSpar alone. Rare cases of intentional overdosage with a fatal outcome were invariably associated with ingestion of multiple drugs and/or alcohol, and a causal relationship to buspirone could not be determined. Toxicology studies of buspirone yielded the following LD50 values: mice, 655 mg/kg; rats, 196 mg/kg; dogs, 586 mg/kg; and monkeys, 356 mg/kg. These dosages are 160 to 550 times the recommended human daily dose.

Bupar Recommended Overdose Treatment
General symptomatic and supportive measures should be used along with immediate gastric lavage. Respiration, pulse, and blood pressure should be monitored as in all cases of drug overdosage. No specific antidote is known to buspirone, and dialyzability of buspirone has not been determined.

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Controlled Substance Class
BuSpar (buspirone hydrochloride) is not a controlled substance.

Buspar Physical and Psychological Dependence
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 BuSpar 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 BuSpar 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 BuSpar misuse or abuse (eg, development of tolerance, incrementation of dose, drug-seeking behavior).

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Buspar Interference with Cognitive and Motor Performance
Studies indicate that BuSpar is less sedating than other anxiolytics and that it does not produce significant functional impairment. However, its CNS effects in any individual patient may not be predictable. Therefore, patients should be cautioned about operating an automobile or using complex machinery until they are reasonably certain that buspirone treatment does not affect them adversely.

While formal studies of the interaction of BuSpar (buspirone hydrochloride) 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.

Buspar Potential for Withdrawal Reactions in Sedative/Hypnotic/Anxiolytic Drug-Dependent Patients
Because BuSpar does not exhibit cross-tolerance with benzodiazepines and other common sedative/hypnotic drugs, it will not block the withdrawal syndrome often seen with cessation of therapy with these drugs. Therefore, before starting therapy with BuSpar, it is advisable to withdraw patients gradually, especially patients who have been using a CNS-depressant drug chronically, from their prior treatment. Rebound or withdrawal symptoms may occur over varying time periods, depending in part on the type of drug, and its effective half-life of elimination.

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.

Buspar Possible Concerns Related to Buspirone’s Binding to Dopamine Receptors
Because buspirone can bind to central dopamine receptors, a question has been raised about its potential to cause acute and chronic changes in dopamine-mediated neurological function (eg, dystonia, pseudo-parkinsonism, akathisia, and tardive dyskinesia). Clinical experience in controlled trials has failed to identify any significant neuroleptic-like activity; however, a syndrome of restlessness, appearing shortly after initiation of treatment, has been reported in some small fraction of buspirone-treated patients. The syndrome may be explained in several ways. For example, buspirone may increase central noradrenergic activity; alternatively, the effect may be attributable to dopaminergic effects (ie, represent akathisia).

Buspar Information for Patients
To assure safe and effective use of BuSpar, the following information and instructions should be given to patients:

1. Inform your physician about any medications, prescription or non-prescription, alcohol, or drugs that you are now taking or plan to take during your treatment with BuSpar.
2. Inform your physician if you are pregnant, or if you are planning to become pregnant, or if you become pregnant while you are taking BuSpar.
3. Inform your physician if you are breast-feeding an infant.
4. Until you experience how this medication affects you, do not drive a car or operate potentially dangerous machinery.
5. You should take BuSpar (buspirone hydrochloride) consistently, either always with or always without food.
6. During your treatment with BuSpar, avoid drinking large amounts of grapefruit juice.

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Psychotropic Agents

MAO inhibitors: It is recommended that BuSpar not  be used concomitantly with MAO inhibitors.

Amitriptyline: After addition of Buspar to the amitriptyline dose regimen, no statistically significant differences in the steady-state pharmacokinetic parameters (Cmax, AUC, and Cmin) of amitriptyline or its metabolite nortriptyline were observed.

Diazepam: After addition of Buspar to the diazepam dose regimen, no statistically significant differences in the steady-state pharmacokinetic parameters (Cmax, AUC, and Cmin) were observed for diazepam, but increases of about 15% were seen for nordiazepam, and minor adverse clinical effects (dizziness, headache, and nausea) were observed.

Haloperidol: In a study in normal volunteers, concomitant administration of Buspar and haloperidol resulted in increased serum haloperidol concentrations. The clinical significance of this finding is not clear.

Trazodone: There is one report suggesting that the concomitant use of Desyrel® (trazodone hydrochloride) and Buspar may have caused 3- to 6-fold elevations on SGPT (ALT) in a few patients. In a similar study attempting to replicate this finding, no interactive effect on hepatic transaminases was identified.

Triazolam/Flurazepam: Coadministration of Buspar with either triazolam or flurazepam did not appear to prolong or intensify the sedative effects of either benzodiazepine.

Other Psychotropics: Because the effects of concomitant administration of Buspar with most other psychotropic drugs have not been studied, the concomitant use of Buspar with other CNS-active drugs should be approached with caution.

Inhibitors and Inducers of Cytochrome P450 3A4 (CYP3A4)

Buspar has been shown in vitro to be metabolized by CYP3A4. This finding is consistent with the in vivo interactions observed between Buspar and the following:

Diltiazem and Verapamil: In a study of nine healthy volunteers, coadministration of Buspar (10 mg as a single dose) with verapamil (80 mg t.i.d.) or diltiazem (60 mg t.i.d.) increased plasma Buspar concentrations (verapamil increased AUC and Cmax of Buspar 3.4-fold while diltiazem increased AUC and Cmax 5.5-fold and 4-fold, respectively.) Adverse events attributable to Buspar may be more likely during concomitant administration with either diltiazem or verapamil. Subsequent dose adjustment may be necessary and should be based on clinical assessment.

Erythromycin: In a study in healthy volunteers, coadministration of Buspar (10 mg as a single dose) with erythromycin (1.5 g/day for 4 days) increased plasma Buspar concentrations (5-fold increase in Cmax and 6-fold increase in AUC). These pharmacokinetic interactions were accompanied by an increased incidence of side effects attributable to Buspar. If the two drugs are to be used in combination, a low dose of Buspar (eg, 2.5 mg b.i.d.) is recommended. Subsequent dose adjustment of either drug should be based on clinical assessment.

Grapefruit Juice: In a study in healthy volunteers, coadministration of Buspar (10 mg as a single dose) with grapefruit juice (200 mL double-strength t.i.d. for 2 days) increased plasma Buspar concentrations (4.3-fold increase in Cmax; 9.2-fold increase in AUC). Patients receiving Buspar should be advised to avoid drinking such large amounts of grapefruit juice.

Itraconazole: In a study in healthy volunteers, coadministration of Buspar (10 mg as a single dose) with itraconazole (200 mg/day for 4 days) increased plasma Buspar concentrations (13-fold increase in Cmax and 19-fold increase in AUC). These pharmacokinetic interactions were accompanied by an increased incidence of side effects attributable to Buspar. If the two drugs are to be used in combination, a low dose of Buspar (eg, 2.5 mg q.d.) is recommended. Subsequent dose adjustment of either drug should be based on clinical assessment.

Nefazodone: In a study of steady-state pharmacokinetics in healthy volunteers, coadministration of Buspar (2.5 or 5 mg b.i.d.) with nefazodone (250 mg b.i.d.) resulted in marked increases in plasma Buspar concentrations (increases up to 20-fold in Cmax and up to 50-fold in AUC) and statistically significant decreases (about 50%) in plasma concentrations of the Buspar metabolite 1-PP. With 5 mg b.i.d. doses of Buspar, slight increases in AUC were observed for nefazodone (23%) and its metabolites hydroxynefazodone (HO-NEF) (17%) and meta-chlorophenylpiperazine (9%). Slight increases in Cmax were observed for nefazodone (8%) and its metabolite HO-NEF (11%). Subjects receiving Buspar 5 mg b.i.d. and nefazodone 250 mg b.i.d experienced lightheadedness, asthenia, dizziness, and somnolence, adverse events also observed with either drug alone. If the two drugs are to be used in combination, a low dose of Buspar (eg, 2.5 mg q.d.) is recommended. Subsequent dose adjustment of either drug should be based on clinical assessment.

Rifampin: In a study in healthy volunteers, coadministration of Buspar (30 mg as a single dose) with rifampin (600 mg/day for 5 days) decreased the plasma concentrations (83.7% decrease in Cmax; 89.6% decrease in AUC) and pharmacodynamic effects of Buspar. If the two drugs are to be used in combination, the dosage of Buspar may need adjusting to maintain anxiolytic effect.

Other Inhibitors and Inducers of CYP3A4: Substances that inhibit CYP3A4, such as ketoconazole or ritonavir, may inhibit Buspar metabolism and increase plasma concentrations of Buspar while substances that induce CYP3A4, such as dexamethasone or certain anticonvulsants (phenytoin, phenobarbital, carbamazepine), may increase the rate of Buspar metabolism. If a patient has been titrated to a stable dosage on Buspar, a dose adjustment of Buspar may be necessary to avoid adverse events attributable to Buspar or diminished anxiolytic activity. Consequently, when administered with a potent inhibitor of CYP3A4, a low dose of Buspar used cautiously is recommended. When used in combination with a potent inducer of CYP3A4 the dosage of Buspar may need adjusting to maintain anxiolytic effect.

Other Drugs

Cimetidine: Coadministration of Buspar with cimetidine was found to increase Cmax (40%) and Tmax (2-fold), but had minimal effects on the AUC of Buspar.

Protein Binding

In vitro, Buspar does not displace tightly bound drugs like phenytoin, propranolol, and warfarin from serum proteins. However, there has been one report of prolonged prothrombin time when Buspar was added to the regimen of a patient treated with warfarin. The patient was also chronically receiving phenytoin, phenobarbital, digoxin, and Synthroid®. In vitro, Buspar may displace less firmly bound drugs like digoxin. The clinical significance of this property is unknown.

Therapeutic levels of aspirin, desipramine, diazepam, flurazepam, ibuprofen, propranolol, thioridazine, and tolbutamide had only a limited effect on the extent of binding of Buspar to plasma proteins.

Synthroid® is the registered trademark of Abbott Laboratories.

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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, Buspar 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 Buspar 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 Buspar.

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Pregnancy Category B: No fertility impairment or fetal damage was observed in reproduction studies performed in rats and rabbits at Buspar doses of approximately 30 times the maximum recommended human dose. In humans, however, adequate and well-controlled studies during pregnancy have not  been performed. Because animal reproduction studies are not always predictive of human response, this drug should be used during pregnancy only if clearly needed.

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