GlaxoSmithKline's Wellbutrin XL

Pharmacy Times, Volume 0, 0

GlaxoSmithKline's Wellbutrin XL (bupropionhydrochloride (HCl) extendedreleasetablets) has received FDA approvalfor the prevention of seasonalaffective disorder (SAD) in adults. Alsoknown as major depressive disorder witha seasonal pattern, SAD is characterizedby depressive symptoms that begin in thefall or winter and subside in the springand summer. The disorder is believed tobe linked to seasonal changes of light.Symptoms often include depressedmood, overeating, weight gain, lethargy,and increased sleep. An estimated 6% ofAmerican adults suffer from SAD.1

Wellbutrin XL is the first medication tobe approved for the prevention of thesymptoms of SAD. It is available as a convenientonce-daily tablet.1,2 Its initial indicationwas for the treatment of majordepressive disorder.2

Mechanism of Action

Although the exact mechanism ofWellbutrin XL is unknown, it is believed toexert noradrenergic and/or dopaminergiceffects through weak inhibition of norepinephrineand dopamine uptake. WellbutrinXL does not inhibit monoamine oxidaseor the reuptake of serotonin.2

Clinical Trials

A total of 3 double-blind, placebo-controlledstudies evaluated the efficacy ofWellbutrin XL for the prevention of SAD inadults with a history of the disorder.Treatment began in the autumn and wasdiscontinued in the spring. The dose wasinitiated at 150 mg daily for 1 week andthen increased to 300 mg daily. Patientswho did not tolerate the 300-mg dosecontinued the 150-mg dose. The combineddata for all 3 trials showed a significantlyhigher rate of depression-freepatients in the Wellbutrin XL group:84.3% in the active group and 72.0% inthe placebo group.1,2

Dosing

As in the clinical trials, the target treatmentperiod for SAD is autumn throughspring. Treatment should be initiated inthe autumn at 150 mg once daily for 1week. If the 150-mg dose is tolerated, itmay be increased to 300 mg daily. Totaldaily doses above 300 mg have not beenstudied. The dose should be tapered to150 mg daily for 2 weeks prior to the discontinuationof treatment in the spring.2

Safety

A worsening of depression or suicidalideation while taking antidepressantshas been noted in both adult and pediatricpopulations. Of specific concern,some short-term studies of antidepressantsin children and adolescents withmajor depressive disorder have shownan increased risk for suicidality. AlthoughWellbutrin XL is indicated only for treatmentin adults 18 years of age and older,all patients using Wellbutrin XL should bemonitored for any changes in mood orbehavior.1,2

Wellbutrin XL is contraindicated inpatients with a current diagnosis of orhistory of seizure disorder, bulimia, oranorexia nervosa. Patients currently takingany other formulations of bupropionor with an allergy to bupropion shouldnot use Wellbutrin XL. Concurrent use ofWellbutrin XL and monoamine oxidaseinhibitors (MAOIs) is contraindicated.Prescribers should allow at least 14 daysbetween discontinuing a MAOI and initiatingtreatment with Wellbutrin XL.Wellbutrin XL is contraindicated inpatients abruptly discontinuing alcoholor sedatives such as benzodiazepines.2Wellbutrin XL should be used cautiouslyin patients with renal and hepaticimpairment. Dose and frequency adjustmentsmay be necessary, and clinicaloutcomes should be monitored closelyfor both efficacy and toxicity.2

Some patients using Wellbutrin XLhave experienced restlessness, agitation,anxiety, and insomnia.2 In clinical trials,the most common side effects were drymouth, nausea, constipation, and flatulence.1

Patient Counseling

Patients should swallow Wellbutrin XLtablets whole, without crushing, chewing,splitting, or cutting them. The tabletsshould be taken at approximately thesame time every day and may be takenwith or without food. If a dose is missed,the patient should wait and take the nextdose at the next scheduled time. Patientsshould contact their doctor immediatelyif signs of a severe allergic reaction,seizure, or unusual thoughts occur.2

Monica Holmberg, PharmDDr. Holmberg is a pharmacist withPhoenix Children's Hospital, Phoenix,Ariz.

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