Bupropion for major depressive disorder: Pharmacokinetic and formulation considerations.

BACKGROUND: Major depressive disorder (MDD) is a common psychiatric condition, with 6.6% of the adult population in the United States experiencing a major depressive episode during any given year. Depressed patients must receive adequate treatment to maximize the likelihood of clinical success. Bupropion hydrochloride, a noradrenergic/dopaminergic antidepressant, is available in 3 oral formulations: immediate release (IR) (given TID), sustained release (SR) (given BID), and extended release (XL) (given QD). Understanding the pharmacokinetic (PK) properties and formulations of bupropion can help optimize clinical use. OBJECTIVES: : The aims of this article were to provide a review of the PK properties of bupropion and identify its various formulations and clinical applications to help optimize treatment of MDD. METHODS: : In this review, data concerning PK trials/reports were collected from articles identified using a PubMed search. The search was conducted without date limitations and using the search terms bupropion, bupropion SR, bupropion XL, bupropion pharmacokinetics, bupropion metabolism, and bupropion drug interactions. Additional reports were selected from references that appeared in articles identified in the original search. In addition, data from studies summarized in product information and labeling were obtained. All available information, concentrating on studies in humans, pertinent to bupropion PK properties and/or formulations was included. RESULTS: : Bupropion is extensively metabolized by the liver (t(1/2), approximately 21 hours). Hydroxybupropion, the primary active metabolite (t(1/2), approximately 20 hours), is formed by cytochrome P450 (CYP) 2B6. At steady state, C(max) of hydroxybupropion is 4- to 7-fold higher, and the AUC is approximately 10-fold greater, compared with those of the parent drug. Threohydrobupropion and erythrohydrobupropion (mean [SD] t(1/2) values, approximately 37 [13] and approximately 33 [10] hours, respectively), the other active metabolites of bupropion, are formed via nonmicrosomal pathways. Relative to bupropion, the C(max) values are approximately 5-fold greater for threohydrobupropion and similar for erythrohydrobupropion. Based on a mouse antitetrabenazine model, hydroxybupropion is approximately 50% as active as bupropion, and threohydrobupropion and erythrohydrobupropion are approximately 20% as active as bupropion. Bupropion lowers the seizure threshold and, therefore, concurrent administration with other agents that lower the seizure threshold should be undertaken cautiously. Potential interactions with other agents that are metabolized by CYP2B6 should be considered. In addition, bupropion inhibits CYP2D6 and may reduce clearance of agents metabolized by this enzyme. Absorption of the XL formulation is prolonged compared with the IR and SR formulations (T(max), approximately 5 hours vs approximately 1.5 and approximately 3 hours, respectively). Bupropion is dosed without regard to food. CONCLUSIONS: : Understanding the PK profile and formulations of bupropion can help optimize clinical use. Bupropion is metabolized extensively, resulting in 3 active metabolites. This metabolic profile, various patient factors (eg, age, medical illnesses), and potential drug interactions should be considered when prescribing bupropion. The 3 formulations-bupropion, bupropion SR, and bupropion XL-are bioequivalent and offer options to optimize treatment for patients with MDD.

15 years of clinical experience with bupropion HCl: from bupropion to bupropion SR to bupropion XL.

BACKGROUND: Bupropion has been available in the United States since 1989. Initially a thrice-daily immediate-release formulation, a twice-daily sustained-release formulation followed in 1996, and, in August 2003, a once-daily extended-release formulation was introduced. On the 15th anniversary of its introduction, we undertook a review of the background/history, mechanism of action, formulations, and clinical profile of bupropion. DATA SOURCES: Major efficacy trials and other reports were obtained and reviewed from MEDLINE searches, review of abstracts from professional meetings, and the bupropion SR manufacturer's databases. Searches of English-language articles were conducted from June 2003 through August 2004. No time limit was specified in the searches, which were conducted using the search terms bupropion, bupropion SR, and bupropion XL. DATA SYNTHESIS: Bupropion inhibits the re-uptake of norepinephrine and dopamine neurotransmission without any significant direct effects on serotonin neurotransmission. Bupropion is an effective antidepressant with efficacy comparable to selective serotonin reuptake inhibitors and other antidepressants. It is well tolerated in short-and longer-term treatment. Headache, dry mouth, nausea, insomnia, constipation, and dizziness are the most common adverse events. Seizure and allergic reactions are medically important adverse events associated with bupropion and are reported rarely. Among all the newer antidepressants in the United States, bupropion appears to have among the lowest incidence of sexual dysfunction, weight gain, and somnolence. Although not U.S. Food and Drug Administration approved for these indications, bupropion has also been used as an adjunctive treatment to reverse antidepressant-induced sexual dysfunction and to augment anti-depressant efficacy in partial responders and non-responders to other agents. CONCLUSION: Bupropion has played and will continue to play an important role as a treatment for major depressive disorder in adults, as well as for other related disorders.

A Review of the Neuropharmacology of Bupropion, a Dual Norepinephrine and Dopamine Reuptake Inhibitor.

BACKGROUND: The neurochemical and biological effects of antidepressant medications have become better defined over the last decade. When the anti-depressant bupropion was introduced in the United States in 1989, the specific pharmacologic basis of its clinical effects was uncertain. Research conducted over the past decade has significantly advanced the understanding of the neuropharmacology of bupropion and has demonstrated a novel mechanism of antidepressant activity. This article discusses the mechanism of action of bupropion and relates the drug's neuropharmacologic effects to its clinical efficacy and tolerability profiles. DATA SOURCES: Data were obtained via the MEDLINE database in an English-language search spanning the period 1965 to May 2002 and using the search terms bupropion, bupropion SR, and antidepressants, as well as from the manufacturer's bupropion databases. CONCLUSIONS: The preclinical and clinical data show that bupropion acts via dual inhibition of norepinephrine and dopamine reuptake and is devoid of clinically significant serotonergic effects or direct effects on postsynaptic receptors. Dual norepinephrine and dopamine reuptake inhibition is associated with a unique clinical profile. Bupropion has demonstrated efficacy comparable to that of other antidepressants. However, because bupropion is a selective norepinephrine and dopamine reuptake inhibitor with no serotonergic activity, common antidepressant-associated side effects, such as sexual dysfunction, weight gain, and sedation, are not associated with bupropion therapy.

Prevalence of sexual dysfunction among newer antidepressants.

BACKGROUND: Sexual dysfunction commonly occurs during antidepressant treatment. However, the reported rates of sexual dysfunction vary across antidepressants and are typically underreported in product literature. The objectives of this study were (1) to estimate the prevalence of sexual dysfunction among patients taking newer antidepressants (bupropion immediate release [IR], bupropion sustained release [SR], citalopram, fluoxetine, mirtazapine, nefazodone, paroxetine, sertraline, venlafaxine, and venlafaxine extended release [XR]) and (2) to compare physician-perceived with patient-reported prevalence rates of antidepressant-associated sexual dysfunction. METHOD: This cross-sectional, observational study was conducted in 1101 U.S. primary care clinics. Adult outpatients (4534 women and 1763 men) receiving antidepressant monotherapy were enrolled. The prevalence of sexual dysfunction was measured using the Changes in Sexual Functioning Questionnaire. RESULTS: In the overall population, bupropion IR (22%) and SR (25%) and nefazodone (28%) were associated with the lowest risk for sexual dysfunction, whereas selective serotonin reuptake inhibitor (SSRI) antidepressants, mirtazapine, and venlafaxine XR were associated with higher rates (36%-43%). In a prospectively defined subpopulation unlikely to have predisposing factors for sexual dysfunction, the prevalence of sexual dysfunction ranged from 7% to 30%, with the odds of having sexual dysfunction 4 to 6 times greater with SSRIs or venlafaxine XR than with bupropion SR. Physicians consistently underestimated the prevalence of antidepressant-associated sexual dysfunction. CONCLUSION: Ours is the first study to assess sexual dysfunction across the newer antidepressants using consistent methodology and a validated rating scale. Overall, SSRIs and venlafaxine XR were associated with higher rates of sexual dysfunction than bupropion or nefazodone. Because antidepressant-associated sexual dysfunction is considerably underestimated by physicians, greater recognition and education are imperative when prescribing antidepressant treatment.