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Bupropion

Drugs & Medication

Bupropion

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Bupropion chemical structure
Bupropion
Systematic (IUPAC) name
(±)-1-(3-chlorophenyl)-2-[(1,1-dimethylethyl)amino]-
1-propanone
Identifiers
CAS number 34841-39-9
ATC code N07BA02
PubChem 444
DrugBank APRD00621
Chemical data
Formula C13H18NClO 
Mol. weight 239.74 g/mol
Pharmacokinetic data
Bioavailability 5 to 20% in animals; no studies in humans
Metabolism Hepatic
Half life 20 hours
Excretion Renal (87%), fecal (10%)
Therapeutic considerations
Pregnancy cat. B(US)
Legal status -only(US)
Routes Oral

Bupropion (or amfebutamone, brand names Wellbutrin and Zyban) is an antidepressant of the aminoketone class, chemically unrelated to tricyclics or selective serotonin reuptake inhibitors (SSRIs). It is similar in structure to the stimulant cathinone, and to phenethylamines in general. It is a chemical derivative of diethylpropion, an amphetamine-like substance used as an anorectic. Bupropion is both a dopamine reuptake inhibitor and a norepinephrine reuptake inhibitor. It is often used as a smoking cessation aid.

International/alternate trade names include Odranal (Colombia), Quomen (Thailand), Well (Korea), Zyban LP (France), Zyban Sustained Release (Australia)

Contents

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 Food and Drug Administration (FDA) as an antidepressant in 1989 and marketed under the name Wellbutrin, 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. It was subsequently discovered that reducing the dose by about half greatly reduced the risk of seizures.

Glaxo then developed a sustained-release (SR) version of Wellbutrin which releases bupropion at a slower rate. The SR formulation is taken twice a day, in order to further decrease the possibility of adverse side effects and seizures. It is also available in generic form (Bupropion SR). Extended Release bupropion, Wellbutrin XL, is the most recent formulation of bupropion and is taken orally once a day. With this altered mechanism of delivery and reduced dosing, incidence of seizures is comparable to, and in some cases lower than, that of other antidepressants. Patients using Bupropion should still be checked for pre-disposing factors that might lead to a lower than normal seizure threshold. It is also important to check for other medications the patient might be using which might also work to lower the seizure threshold.

In 1997, bupropion (as bupropion hydrochloride) was approved by the FDA for use as a smoking cessation aid. Glaxo subsequently marketed the drug under the name Zyban to help people stop smoking tobacco by reducing the severity of nicotine cravings and addiction/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.

Bupropion is also being investigated for several other disorders including overweight or obesity, attention-deficit hyperactivity disorder, restless legs syndrome and a possible treatment for increasing sexual functioning in some women. In late 2006, Wellbutrin XL was approved for use by the FDA as treatment for seasonal affective disorder.

GlaxoSmithKline's exclusivity patent ended in early 2004. Prior to this, there were several patent suits, the biggest of which involved the pharmaceutical company called Andrx in 1999. After an intitial dismissal of the case in 2003, several court appeals by Glaxo resulted in the refiling of the case. The suit is still pending.[1]

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 antidepressant effect of bupropion is considered to be mediated by its dopaminergic and noradrenergic action. Bupropion has also been shown to act as a competitive α3β4 nicotinic antagonist, the α3β4-antagonism has been shown to interrupt addiction in studies of other drugs such as ibogaine. This α3β4-antagonism correlates quite well with the observed effect of interrupting addiction.

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 is 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.

Contraindications

  • Epilepsy and other conditions that lower the seizure threshold (alcohol withdrawal, active brain tumors etc.)
    Concomitant treatment with MAO inhibitors. When switching medications it is important that there be a short period of about two weeks between the medications in order to reduce risk of complications that might lead to things such as a decrease in seizure threshold.
    Caution with the concomitant use of sympathomimetic drugs (e.g. ephedrine)
    Active liver damage (e.g. cirrhosis)
    Anorexia nervosa and bulimia which might lead the patient to have a decreased seizure threshold
    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 (risk is no higher than any other antidepressant)

Side effects

Common side effects include dry mouth, tremors, anxiety, loss of appetite, agitation, dizziness, headache, excessive sweating such as night sweats, increased risk of seizure (Its most controversial side effect, found in 4/1000 during trials), aggressiveness, and both initial and terminal insomnia. Activation of mania and psychosis have both been encountered. Some patients may also require less than the normal dosing which usually starts at around 150 mg for the first few weeks and is then switched to the normal 300 mg dosage; these patients may be kept on the 150 mg regimen.

Suicidal thoughts and attempts have been reported in children and adolescents. Reports of increasing suicidal thoughts have occurred.

Scattered abnormalities of liver function tests are noted, without evidence of hepatotoxicity. Cases of significant liver damage with or without jaundice (icterus) have been seen rarely. In a German database covering side effects, five cases of pancreatitis with elevations of serum-amylase and lipase as well as clinical symptoms (e.g. abdominal pain, anorexia), reversible after termination of bupropion, have been reported. Currently, it is unclear whether preexisting alcohol abuse or dependence might predispose patients to develop pancreatitis.

Infrequently, dose-dependent hypertension is noted. Single cases of myocardial infarction (heart attack) have been noted, but the causal association to the use of bupropion is currently unknown.

The development of mild to moderate skin rashes associated with sensitivity to dye components within the pill coating. This can often be alleviated by simply prescribing a different color pill and consequently, changing the dosage.

Few cases of the urological emergency priapism (painful erection) have been seen. Immediate treatment is necessary, because the untreated patient may totally lose his ability to have erections.

Interactions

Quite a great number of drugs show clinically significant interactions with bupropion. This may be due to interactions with drugs that are metabolized by CYP2D6 as bupropion inhibits CYP2D6 activity. However, bupropion is not metabolized by CYP2D6.

Manufacturer studies have also indicated that bupropion is primarily metabolized to hydroxybupropion by the CYP2B6 isoenzyme. Theoretically, drug interactions could occur between bupropion and substrates or inhibitors of CYP2B6 (e.g. orphenadrine, thiotepa, or cyclophosphamide).

Bupropion is known to lower the seizure threshold. Bupropion, in combination with other medications, has been suspected to induce seizures in some patients with no prior record of seizure activity.[1] While this is not a common side-effect, a growing number of cases world wide validate the need for consideration. It is not uncommon for patients to receive treatment with other antidepressant and/or atypical antipsychotic medications in combination with bupropion. For this reason, care should be taken when prescribing bupropion with other medications prone to lower the seizure threshold. Bupropion has also been known to produce seizures in combination with non-prescription (recreational) drugs such as cocaine, and alcohol. Study the packing insert carefully and ask your prescribing physician about possible interactions.

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 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 practice, 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.

Dosage

  • Depression: the target dosage is 300 mg daily, starting with 150 mg in the first few days. If indicated and directed by physician, the dosage may be increased to a maximum of 450 mg daily.
  • Tobacco withdrawal: 150 mg initially, may be increased to 300 mg if indicated and directed by physician. In patients also receiving insulin, sympathomimetic anorectical drugs, or antimalaria agents, the daily dose of bupropion should not exceed 150 mg.

Dose forms

Brand and generic pills are available in three forms: immediate release, sustained release (SR), and extended release (XL, ER).

Brand Name Dosage Color
Wellbutrin 75 mg yellow-gold
Wellbutrin 100 mg red
Wellbutrin SR 100 mg blue
Wellbutrin SR 150 mg purple
Wellbutrin SR 200 mg pink
Wellbutrin XL 150 mg white
Wellbutrin XL 300 mg white
Zyban SR 150 mg purple


Overdosage

GlaxoSmithKline has reported that overdoses of up to 30 g or more of Wellbutrin (bupropion) had resulted in seizure in about one third of all cases. Hallucinations, loss of consciousness, sinus tachycardia, and ECG changes such as conduction disturbances or arrhythmias were reported as other serious reactions of overdoses of bupropion alone. Multiple overdoses including bupropion had resulted in fever, rhabdomyolysis, stupor, hypotension, coma, muscle rigidity, and respiratory failure.[2]

Additional warnings

May cause false-positive for amphetamine

Bupropion contains a similar pharmacological structure to that of amphetamines. In most cases prescription medications that contain bupropion ( Wellbutrin, Zyban ) will produce a positive result for amphetamine abuse.

Use in pediatric patients

Bupropion has been shown to increase the incidence of suicidal thoughts and attempts in children and adolescents with depression. When treating major depressive disorder in this group of patients, clinical benefits should be weighed carefully against therapeutic hazards. Usually, bupropion is not indicated for pediatric patients under age 18.[3]

Potential indications of bipolar and schizoaffective disorder

The effects of bupropion in treating eleven patients with bipolar or schizoaffective disorder were examined in an open trial.[4] Most patients had been intolerant of or showed minimal to moderate improvement on lithium, neuroleptics, antidepressants, or a combination of these drugs. All patients were maintained on bupropion alone or bupropion in combination with low-dose neuroleptics or anxiolytics for one year or more, with little or no relapse and few side effects. Although these results are encouraging, additional larger studies need to be conducted to confirm this indication.

Alleged risks with certain treatments

In the UK, more than 7,000 reports of potential hazardous side effects have been collected. There have been 44 reports of suspected adverse reactions where there was a fatal outcome while taking Zyban. In reviewing these cases the MHRA state that in the majority of cases the individual’s underlying condition may provide an alternative explanation.[5] More than two thirds of reported deaths were from cardio-vascular or cerebro-vascular causes. A case-series analysis showed increased risk of seizure in the population taking bupropion, but no increase in the risk of sudden death.[6] At least 107 cases of serious side effects have been reported in Germany. Wellbutrin is also banned or restricted from use in several countries.

In the UK, bupropion should only be prescribed as an aid in quitting smoking to smokers who have committed to a definite quit date and a prescription will not last more than 4 weeks after this target date. NICE has issued guidance to the effect that if the attempt to quit is unsuccessful the NHS will not provide funding for a further course, for at least 6 months.

In some countries bupropion is approved only as a smoking cessation aid and not for treatment of depression.

Studies of juveniles with depression

A large study gathered the results of twenty-four studies of juveniles with depression. Patients were to take either a placebo (sugar pill) or an antidepressant (SSRIs and others, including bupropion) for one to four months. According to the results, nobody committed suicide in these studies, although two out of every hundred patients became suicidal on a placebo and four out of every hundred become suicidal on antidepressants. Results indicated that the risks of suicidal actions become high for some juveniles. These kinds of juveniles may include patients with:[2]

  • Bipolar illness, previously known as manic-depressive illness
  • A family history of bipolar illness
  • A personal or family history of attempting or committing suicide

References

  1. ^ Pesola G, Avasarala J (2002). "Bupropion seizure proportion among new-onset generalized seizures and drug related seizures presenting to an emergency department.". J Emerg Med 22 (3): 235-9. PMID 11932084.
  2. ^ a b Wellbutrin XL® Prescribing Information. GlaxoSmithKline (June 2006).
  3. ^ Antidepressant Use in Children, Adolescents, and Adults – Medication Guide Template. United States Food and Drug Administration (FDA) (January 26, 2005). Retrieved on 2006-10-07.
  4. ^ Wright G, Galloway L, Kim J, Dalton M, Miller L, Stern W (1985). "Bupropion in the long-term treatment of cyclic mood disorders: mood stabilizing effects.". J Clin Psychiatry 46 (1): 22-5. PMID 2856918.
  5. ^ Zyban (bupropion hydrochloride) – safety update. Medicines and Healthcare products Regulatory Agency (July 24, 2002). Retrieved on 2006-10-07.
  6. ^ Hubbard R, Lewis S, West J, Smith C, Godfrey C, Smeeth L, Farrington P, Britton J (2005). "Bupropion and the risk of sudden death: a self-controlled case-series analysis using The Health Improvement Network.". Thorax 60 (10): 848-50. PMID 16055620.

Further reading

External links


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This guide is licensed under the GNU Free Documentation License. It uses material from the Wikipedia.


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