Basic and Clinical pharmacology

Wellbutrin is a brand name for bupropion, an atypical and a second generation antidepressant drug of aminoketone class. Its structure is different from tricyclic and other known antidepressant. Its structure resembles that of diethylpropion. The powder is white crystalline and highly soluble in water, it produces sensation of local anesthesia on oral mucosa. Wellbutrin is supplied for oral administration in 200-450 mg per day. Each tablet contains bupropion hydrochloride and some inactive ingredient like cellulose, glycol, talc, and so on. It is produced by Glaxosmithkline pharmaceutics.

Depression is a state in which there is a severe depressed mood{for more than 2 weeks},and loss of interest or pleasure in usual activities accompanied by sleep and appetite disturbances, agitation or lack of energy, feeling of guilt or worthlessness, decreased sex drive, inability to concentrate, and sometimes, suicidal thought or behavior. USAGE Wellbutrin is prescribed to help relieve major depression. It can be in form of a normal oral Wellbutrin, or in sustained-released tablet form {Wellbutrin SR} or in extended-released tablet {Wellbutrin XR}.

It is also used in the treatment of seasonal affective disorder {SAD}: episode of depression that occurs in the fall and winter each year. It is also used to treat depressed patient with bipolar disorder, like manic-depressive disorder and attention deficit disorder i. e. more difficulty focusing, controlling action, and remaining still or quiet. The drug is usually taken 3 times a day, with doses at least 6 hours apart, the sustained released tablet is usually taken twice a day, with doses 8 hours apart while the extended release type is usually taken once daily usually in the morning, as they can cause insomnia if taken late.

The sustained released tablet also appears to be effective as nicotine replacement therapy in recent trials, even in non depressed patients, and has fewer side effects. The usual adult dose is 300mg per day, though dosing should begin with 200mg per day at 100mg 2 times daily, it can be increased later to 300mg. The full antidepressant effect of Wellbutrin may not be evident until about 4 weeks of treatment or longer. In patient in whom no clinical improvement is seen at 300 mg, the dose can be increased to 450mg per day at maximum. This is given as 150mg 3 times in a day.

Treatment should be discontinued in a patient that shows no adequate responds after appropriate period of time. CLINICAL PHARMACOLOGY Wellbutrin???? s neurochemical mechanism of its antidepressant effect is still a subject of research, it does not inhibit monoamine oxidase [MAO}, but it is a weak blocker of the neuronal uptake of serotonin and norepinephrine. It sometimes inhibits the reuptake of dopamine. The peak plasma of the drug following an oral administration are achieved within 2 hours, followed by a biphasic decline, 6 hours after a single dose the plasma bupropion concentration are approximately 30% of the peak concentration.

It has a short half life and thus required more than once a day doses except for the extended released formulation. It appeared that only a small amount of the orally administered dose reaches the systemic circulation intact i. e. low bioavailability. METABOLISM After oral administration, the pharmacokinetics is similar to that of the tricyclics antidepressant. Fraction excreted was only 0. 5% of the drug in a research. Several known metabolites of bupropion are pharmacological active though their potency has not been fully characterized. It has been shown that bupropion induce its own metabolism following a subchronic administration.

The urinary and plasma metabolite are product of reduction and hydroxylation processes, these include morpholinor, erythro-amine diol. CONTRAINDICATIONS The drug should not be used when taking a monoamine oxidase {MAO} inhibitor, such as isocarboxazid, selegitive etc, beta blockers, such as atenolol, labetol, diet pill, insulin or oral medication for diabetics, medication for irregular heartbeat like flecainide, oral steroids like dexamethasone, prednisone, sleeping pills, like thiophyline, and other antidepressant drugs like despiramine and flouxetine.

It is also contraindicated in patient with seizure disorder. OVERDOSE. Though this is not a common occurrence, It has been reported that massive dose of Wellbutrin can result to difficulty in breathing or swallow, fainting, dizziness, sweating, confusion, blurred vision, seizure, hallucination,{seeing things or hearing voices that do not exist} loss of consciousness, rapid or pounding heartbeat, lightheadedness, lack of energy, upset stomach, muscle rigidity, and so on. Though patient recovers without much complication, death has been recorded in some patient.

It is advisable to hospitalize overdose patient and if the patient is conscious, vomiting should be induced, but if the patient is comatose, airway intubation can be done prior to gastric levage. SIDE EFFECTS When taking the drug, some reaction might be noticed, these include drowsiness, dry mouth, tremor, aggravation of psychosis, headache, myalgia, and fever associated with rash. The more seriously depressed the patient, the more likely it is that the unwanted effect will be tolerated.

Study shows that some number of children, teenagers and young adult who took antidepressant such as Wellbutrin, during clinical studies, become suicidal {thinking about harming or killing oneself }so it not advisable to recommend Wellbutrin to a children younger than 18 years.

Reference: Basic and Clinical pharmacology (Bertrum G. katzung) ninth edition (2004) Pharmacology; H. P Rang, M. M Dale, J. M Ritters (5th Edition) www. mentalhealth. com www. healthsquare. com/newrx/we11488. htm

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