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History
bupropion was first synthesized by Burroughs Research in 1966, and patented by Burroughs-Wellcome (later Glaxo-Wellcome, and, as of 2000, GlaxoSmithKline) in 1974. It was approved by the FDA in 1985 and marketed under the name Wellbutrin as an antidepressant, but clinical trials indicated that incidence of seizure was two to four times greater than other antidepressants and the drug was quickly pulled from the market. Glaxo, realizing that seizure risk was a function of dosage, then developed and marketed a sustained-release (SR) version of Wellbutrin which, when ingested, releases bupropion hydrochloride at a constant, gradual rate into the body. Because of this altered mechanism of delivery, incidence of seizure with Wellbutrin.buy.blogopt.com]Wellbutrin-SR[/url] is comparable to, and in some cases, lower than that of other antidepressants.
In 1997, bupropion HCl was approved by the FDA for use as a smoking cessation aid. Because the name Wellbutrin was still associated with high seizure risk, Glaxo subsequently marketed the drug under the name Zyban to help people stop smoking tobacco by reducing the severity of withdrawal symptoms. It can be used in combination with nicotine replacement therapies. bupropion treatment course lasts for seven to twelve weeks, with the patient halting the use of tobacco around ten days into the course.
Mode of action
bupropion is a selective catecholamine (norepinephrine and dopamine) reuptake inhibitor. It has only a small effect on serotonin reuptake. It does not inhibit MAO. The actual mechanism behind bupropion\'s action is not known, but it is thought to be due to the effects on dopaminergic and noradrenergic mechanisms.
Pharmacokinetics
bupropion is metabolised in the liver. It has at least three active metabolites: hydroxybupropion, threohydrobupropion and erythrohydrobupropion. These active metabolites are further metabolised to inactive metabolites and eliminated through excretion into the urine. The half-life of bupropion is 20 hours as is hydroxybupropion\'s. Threohydrobupropion\'s half-life is 37 hours and erythrohydrobupropion\'s 33 hours.
Chronic hepatotoxicity in animals
In rats receiving large doses of bupropion chronically, there was an increase in incidence of hepatic hyperplastic nodules and hepatocellular hypertrophy. In dogs receiving large doses of bupropion chronically, various histologic changes were seen in the liver, and laboratory tests suggesting mild hepatocellular injury were noted.
Indications
management of depression
adjunctive in tobacco withdrawal
attention deficit disorder
Contraindications
epilepsy and other conditions that lower the seizure-threshold (alcohol withdrawal, active brain tumors etc.)
concomitant treatment with MAO-Inhibitors
caution with the concomitant use of sympathomimetic drugs (e.g. Ephedrine)
active liver damage (e.g. cirrhosis)
anorexia, bulimia
severe kidney disease
severe hypertension
anxiety disorders (caution), agitated patients
pediatric patients (see below)
use considerable caution in treating patients where suicide may be a risk
Interactions
Quite a great number of drugs show clinically significant interactions with bupropion. Study the packing insert carefully and ask your prescribing physician in any case of doubt.
Abuse liability
In animal studies and small studies with persons having experience with the use of amphetamines or cocaine, bupropion caused drug-seeking behaviour (animal experiments) and was recognized as an amphetamine-like drug by the humans. In a scale ranging from placebo on the lower side to benzedrine, it was given an intermediate score indicating moderate likelihood of abuse. In clinical practise, bupropion has been shown that the dose required for significant abuse would cause seizures in most patients. Abuse has not become a significant problem in clinical usage, but the drug should be given with caution to patients with a history of drug or alcohol abuse or dependence. bupropion is not a controlled substance.
Limitation to tobacco withdrawal
In some countries bupropion is approved only as a smoking cessation aid and not for treatment of depression.
Influence on sexual function/libido
An advantage of bupropion over most conventional antidepressants is that it causes no sexual dysfunction in men and may even increase libido. According to a recent study, bupropion does also increase libido in women with \"hypoactive sexual desire disorder\" but without signs of depression. It is too early to come to conclusive evidence whether to treat these women or not. Further controlled studies are required. |
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