Zyban (bupropion hydrochloride) Sustained-Release Tablets are a non-nicotine aid to smoking cessation. Zyban is chemically unrelated to nicotine or other agents currently used in the treatment of nicotine addiction. Initially developed and marketed as an antidepressant (WELLBUTRIN [bupropion hydrochloride] Tablets and WELLBUTRIN SR [bupropion hydrochloride] Sustained-Release Tablets), Zyban is also chemically unrelated to tricyclic, tetracyclic, selective serotonin re-uptake inhibitor, or other known antidepressant agents. Its structure closely resembles that of diethylpropion; it is related to phenylethylamines. It is (±)-1-(3-chlorophenyl)-2-[(1,1-dimethylethyl)amino]-1-propanone hydrochloride. The molecular weight is 276.2. The molecular formula is C13H18ClNO•HCl. Bupropion hydrochloride powder is white, crystalline, and highly soluble in water. It has a bitter taste and produces the sensation of local anesthesia on the oral mucosa. The structural formula is:
Zyban is supplied for oral administration as 150-mg (purple), film-coated, sustained-release tablets. Each tablet contains the labeled amount of bupropion hydrochloride and the inactive ingredients carnauba wax, cysteine hydrochloride, hypromellose, magnesium stearate, microcrystalline cellulose, polyethylene glycol, polysorbate 80 and titanium dioxide and is printed with edible black ink. In addition, the 150-mg tablet contains FD&C Blue No. 2 Lake and FD&C Red No. 40 Lake.
Zyban - Clinical Pharmacology
Pharmacodynamics
Bupropion is a relatively weak inhibitor of the neuronal uptake of norepinephrine and dopamine, and does not inhibit monoamine oxidase or the re-uptake of serotonin. The mechanism by which Zyban enhances the ability of patients to abstain from smoking is unknown. However, it is presumed that this action is mediated by noradrenergic and/or dopaminergic mechanisms.
Pharmacokinetics
Bupropion is a racemic mixture. The pharmacologic activity and pharmacokinetics of the individual enantiomers have not been studied. Bupropion follows biphasic pharmacokinetics best described by a 2-compartment model. The terminal phase has a mean half-life (±% CV) of about 21 hours (±20%), while the distribution phase has a mean half-life of 3 to 4 hours.
Absorption: Bupropion has not been administered intravenously to humans; therefore, the absolute bioavailability of Zyban in humans has not been determined. In rat and dog studies, the bioavailability of bupropion ranged from 5% to 20%.
Following oral administration of Zyban to healthy volunteers, peak plasma concentrations of bupropion are achieved within 3 hours. The mean peak concentration (Cmax) values were 91 and 143 ng/mL from 2 single-dose (150-mg) studies. At steady state, the mean Cmax following a 150-mg dose every 12 hours is 136 ng/mL.
Exposure to bupropion may be increased when Zyban tablets are taken with food. Three studies in healthy volunteers demonstrated peak plasma concentrations (Cmax) of bupropion increased by 11% to 35% when administered with food, while overall exposure (AUC) to bupropion increased by 16% to 19%. The food effect is not considered clinically significant and Zyban can be taken with or without food.
Distribution: In vitro tests show that bupropion is 84% bound to human plasma proteins at concentrations up to 200 mcg/mL. The extent of protein binding of the hydroxybupropion metabolite is similar to that for bupropion, whereas the extent of protein binding of the threohydrobupropion metabolite is about half that seen with bupropion. The volume of distribution (Vss/F) estimated from a single 150-mg dose given to 17 subjects is 1,950 L (20% CV).
Metabolism: Bupropion is extensively metabolized in humans. Three metabolites have been shown to be active: hydroxybupropion, which is formed via hydroxylation of the tert-butyl group of bupropion, and the amino-alcohol isomers threohydrobupropion and erythrohydrobupropion, which are formed via reduction of the carbonyl group. In vitro findings suggest that cytochrome P450IIB6 (CYP2B6) is the principal isoenzyme involved in the formation of hydroxybupropion, while cytochrome P450 isoenzymes are not involved in the formation of threohydrobupropion. Oxidation of the bupropion side chain results in the formation of a glycine conjugate of meta-chlorobenzoic acid, which is then excreted as the major urinary metabolite. The potency and toxicity of the metabolites relative to bupropion have not been fully characterized. However, it has been demonstrated in an antidepressant screening test in mice that hydroxybupropion is one-half as potent as bupropion, while threohydrobupropion and erythrohydrobupropion are 5-fold less potent than bupropion. This may be of clinical importance because the plasma concentrations of the metabolites are as high or higher than those of bupropion.
Because bupropion is extensively metabolized, there is the potential for drug-drug interactions, particularly with those agents that are metabolized by or which inhibit/induce the cytochrome P450IIB6 (CYP2B6) isoenzyme, such as ritonavir or efavirenz. In a healthy volunteer study, ritonavir at a dose of 100 mg twice daily reduced the AUC and Cmax of bupropion by 22% and 21%, respectively. The exposure of the hydroxybupropion metabolite was decreased by 23%, the threohydrobupropion decreased by 38%, and the erythrohydrobupropion decreased by 48%.
In a second healthy volunteer study, ritonavir at a dose of 600 mg twice daily decreased the AUC and the Cmax of bupropion by 66% and 62%, respectively. The exposure of the hydroxybupropion metabolite was decreased by 78%, the threohydrobupropion decreased by 50%, and the erythrohydrobupropion decreased by 68%.
In another healthy volunteer study, KALETRA® (lopinavir 400 mg/ritonavir 100 mg twice daily) decreased bupropion AUC and Cmax by 57%. The AUC and Cmax of hydroxybupropion were decreased by 50% and 31%, respectively (see PRECAUTIONS: Drug Interactions).
In a study in healthy volunteers, efavirenz 600 mg once daily for 2 weeks reduced the AUC and Cmaxof bupropion by approximately 55% and 34%, respectively. The AUC of hydroxybupropion was unchanged, whereas Cmaxof hydroxybupropion was increased by 50%.
Although bupropion is not metabolized by cytochrome P450IID6 (CYP2D6), there is the potential for drug-drug interactions when bupropion is coadministered with drugs metabolized by this isoenzyme (see PRECAUTIONS: Drug Interactions).
Following a single dose in humans, peak plasma concentrations of hydroxybupropion occur approximately 6 hours after administration of Zyban. Peak plasma concentrations of hydroxybupropion are approximately 10 times the peak level of the parent drug at steady state. The elimination half-life of hydroxybupropion is approximately 20 (±5) hours and its AUC at steady state is about 17 times that of bupropion. The times to peak concentrations for the erythrohydrobupropion and threohydrobupropion metabolites are similar to that of the hydroxybupropion metabolite; however, their elimination half-lives are longer, 33 (±10) and 37 (±13) hours, respectively, and steady-state AUCs are 1.5 and 7 times that of bupropion, respectively.
Bupropion and its metabolites exhibit linear kinetics following chronic administration of 300 to 450 mg/day.
Elimination: The mean (±% CV) apparent clearance (Cl/F) estimated from 2 single-dose (150-mg) studies are 135 (±20%) and 209 L/hr (±21%). Following chronic dosing of 150 mg of Zyban every 12 hours for 14 days (n = 34), the mean Cl/F at steady state was 160 L/hr (±23%). The mean elimination half-life of bupropion estimated from a series of studies is approximately 21 hours. Estimates of the half-lives of the metabolites determined from a multiple-dose study were 20 hours (±25%) for hydroxybupropion, 37 hours (±35%) for threohydrobupropion, and 33 hours (±30%) for erythrohydrobupropion. Steady-state plasma concentrations of bupropion and metabolites are reached within 5 and 8 days, respectively.
Following oral administration of 200 mg of 14C-bupropion in humans, 87% and 10% of the radioactive dose were recovered in the urine and feces, respectively. The fraction of the oral dose of bupropion excreted unchanged was only 0.5%.
The effects of cigarette smoking on the pharmacokinetics of bupropion were studied in 34 healthy male and female volunteers; 17 were chronic cigarette smokers and 17 were nonsmokers. Following oral administration of a single 150-mg dose of Zyban, there was no statistically significant difference in Cmax, half-life, Tmax, AUC, or clearance of bupropion or its major metabolites between smokers and nonsmokers.
In a study comparing the treatment combination of Zyban and nicotine transdermal system (NTS) versus Zyban alone, no statistically significant differences were observed between the 2 treatment groups of combination Zyban and NTS (n = 197) and Zyban alone (n = 193) in the plasma concentrations of bupropion or its active metabolites at weeks 3 and 6.
Population Subgroups
Factors or conditions altering metabolic capacity (e.g., liver disease, congestive heart failure [CHF], age, concomitant medications, etc.) or elimination may be expected to influence the degree and extent of accumulation of the active metabolites of bupropion. The elimination of the major metabolites of bupropion may be affected by reduced renal or hepatic function because they are moderately polar compounds and are likely to undergo further metabolism or conjugation in the liver prior to urinary excretion.
Hepatic:The effect of hepatic impairment on the pharmacokinetics of bupropion was characterized in 2 single-dose studies, one in patients with alcoholic liver disease and one in patients with mild-to-severe cirrhosis. The first study showed that the half-life of hydroxybupropion was significantly longer in 8 patients with alcoholic liver disease than in 8 healthy volunteers (32 ± 14 hours versus 21 ± 5 hours, respectively). Although not statistically significant, the AUCs for bupropion and hydroxybupropion were more variable and tended to be greater (by 53% to 57%) in patients with alcoholic liver disease. The differences in half-life for bupropion and the other metabolites in the 2 patient groups were minimal.
The second study showed that there were no statistically significant differences in the pharmacokinetics of bupropion and its active metabolites in 9 patients with mild-to-moderate hepatic cirrhosis compared to 8 healthy volunteers. However, more variability was observed in some of the pharmacokinetic parameters for bupropion (AUC, Cmax, and Tmax) and its active metabolites (t½) in patients with mild-to-moderate hepatic cirrhosis. In addition, in patients with severe hepatic cirrhosis, the bupropion Cmax and AUC were substantially increased (mean difference: by approximately 70% and 3-fold, respectively) and more variable when compared to values in healthy volunteers; the mean bupropion half-life was also longer (29 hours in patients with severe hepatic cirrhosis vs. 19 hours in healthy subjects). For the metabolite hydroxybupropion, the mean Cmax was approximately 69% lower. For the combined amino-alcohol isomers threohydrobupropion and erythrohydrobupropion, the mean Cmax was approximately 31% lower. The mean AUC increased by 28% for hydroxybupropion and 50% for threo/erythrohydrobupropion. The median Tmax was observed 19 hours later for hydroxybupropion and 21 hours later for threo/erythrohydrobupropion. The mean half-lives for hydroxybupropion and threo/erythrohydrobupropion were increased 2- and 4-fold, respectively, in patients with severe hepatic cirrhosis compared to healthy volunteers (see WARNINGS, PRECAUTIONS, and DOSAGE AND ADMINISTRATION).
Renal: There is limited information on the pharmacokinetics of bupropion in patients with renal impairment. An inter-study comparison between normal subjects and patients with end-stage renal failure demonstrated that the parent drug Cmax and AUC values were comparable in the 2 groups, whereas the hydroxybupropion and threohydrobupropion metabolites had a 2.3– and 2.8–fold increase, respectively, in AUC for patients with end-stage renal failure. A second study, comparing normal subjects and patients with moderate-to-severe renal impairment (GFR 30.9 ± 10.8 mL/min) showed that exposure to a single 150-mg dose of sustained-release bupropion was approximately 2-fold higher in patients with impaired renal function while levels of the hydroxybupropion and threo/erythrohydrobupropion (combined) metabolites were similar in the 2 groups. The elimination of bupropion and/or the major metabolites of bupropion may be reduced by impaired renal function (see PRECAUTIONS: Renal Impairment).
Left Ventricular Dysfunction: During a chronic dosing study with bupropion in 14 depressed patients with left ventricular dysfunction (history of CHF or an enlarged heart on x-ray), no apparent effect on the pharmacokinetics of bupropion or its metabolites, compared to healthy normal volunteers, was revealed.
Age: The effects of age on the pharmacokinetics of bupropion and its metabolites have not been fully characterized, but an exploration of steady-state bupropion concentrations from several depression efficacy studies involving patients dosed in a range of 300 to 750 mg/day, on a 3-times-a-day schedule, revealed no relationship between age (18 to 83 years) and plasma concentration of bupropion. A single-dose pharmacokinetic study demonstrated that the disposition of bupropion and its metabolites in elderly subjects was similar to that of younger subjects. These data suggest there is no prominent effect of age on bupropion concentration; however, another pharmacokinetic study, single and multiple dose, has suggested that the elderly are at increased risk for accumulation of bupropion and its metabolites (see PRECAUTIONS: Geriatric Use).
Gender: A single-dose study involving 12 healthy male and 12 healthy female volunteers revealed no sex-related differences in the pharmacokinetic parameters of bupropion.
Clinical Trials
The efficacy of Zyban as an aid to smoking cessation was demonstrated in 3 placebo-controlled, double-blind trials in nondepressed chronic cigarette smokers (n = 1,940, ≥15 cigarettes per day). In these studies, Zyban was used in conjunction with individual smoking cessation counseling.
The first study was a dose-response trial conducted at 3 clinical centers. Patients in this study were treated for 7 weeks with 1 of 3 doses of Zyban (100, 150, or 300 mg/day) or placebo; quitting was defined as total abstinence during the last 4 weeks of treatment (weeks 4 through 7). Abstinence was determined by patient daily diaries and verified by carbon monoxide levels in expired air.
Results of this dose-response trial with Zyban demonstrated a dose-dependent increase in the percentage of patients able to achieve 4-week abstinence (weeks 4 through 7). Treatment with Zyban at both 150 and 300 mg/day was significantly more effective than placebo in this study.
Table 1 presents quit rates over time in the multicenter trial by treatment group. The quit rates are the proportions of all persons initially enrolled (i.e., intent-to-treat analysis) who abstained from week 4 of the study through the specified week. Treatment with Zyban (150 or 300 mg/day) was more effective than placebo in helping patients achieve 4-week abstinence. In addition, treatment with Zyban (7 weeks at 300 mg/day) was more effective than placebo in helping patients maintain continuous abstinence through week 26 (6 months) of the study.
Table 1. Dose-Response Trial: Quit Rates by Treatment Group
Abstinence From Week 4 Through Specified Week
|
Treatment Groups
|
Placebo (n = 151)
%
(95% CI)
|
Zyban 100 mg/day (n = 153)
%
(95% CI)
|
Zyban 150 mg/day
(n = 153)
%
(95% CI)
|
Zyban 300 mg/day (n = 156)
%
(95% CI)
|
|
Week 7 (4-week quit)
|
17%
(11-23)
|
22%
(15-28)
|
27%a
(20-35)
|
36%a
(28-43)
|
Week 12
|
14%
(8-19)
|
20%
(13-26)
|
20%
(14-27)
|
25%a
(18-32)
|
Week 26
|
11%
(6-16)
|
16%
(11-22)
|
18%
(12-24)
|
19%a
(13-25)
|
a Significantly different from placebo (P≤0.05).
The second study was a comparative trial conducted at 4 clinical centers. Four treatments were evaluated: Zyban 300 mg/day, nicotine transdermal system (NTS) 21 mg/day, combination of Zyban 300 mg/day plus NTS 21 mg/day, and placebo. Patients were treated for 9 weeks. Treatment with Zyban was initiated at 150 mg/day while the patient was still smoking and was increased after 3 days to 300 mg/day given as 150 mg twice daily. NTS 21 mg/day was added to treatment with Zyban after approximately 1 week when the patient reached the target quit date. During weeks 8 and 9 of the study, NTS was tapered to 14 and 7 mg/day, respectively. Quitting, defined as total abstinence during weeks 4 through 7, was determined by patient daily diaries and verified by expired air carbon monoxide levels. In this study, patients treated with any of the 3 treatments achieved greater 4-week abstinence rates than patients treated with placebo.
Table 2 presents quit rates over time by treatment group for the comparative trial.
Table 2. Comparative Trial: Quit Rates by Treatment Group
Abstinence From Week 4 Through Specified Week
|
Treatment Groups
|
Placebo (n = 160)
%
(95% CI)
|
Nicotine Transdermal System (NTS) 21 mg/day (n = 244)
%
(95% CI)
|
Zyban 300 mg/day (n = 244)
%
(95% CI)
|
Zyban 300 mg/day and NTS 21 mg/day (n = 245)
%
(95% CI)
|
|
Week 7 (4-week quit)
|
23%
(17-30)
|
36%
(30-42)
|
49%
(43-56)
|
58%
(51-64)
|
Week 10
|
20%
(14-26)
|
32%
(26-37)
|
46%
(39-52)
|
51%
(45-58)
|
When patients in this study were followed out to one year, the superiority of Zyban and the combination of Zyban and NTS over placebo in helping patients to achieve abstinence from smoking was maintained. The continuous abstinence rate was 30% (95% CI 24-35) in the patients treated with Zyban, and 33% (95% CI 27-39) for patients treated with the combination at 26 weeks compared with 13% (95% CI 7-18) in the placebo group. At 52 weeks, the continuous abstinence rate was 23% (95% CI 18-28) in the patients treated with Zyban , and 28% (95% CI 23-34) for patients treated with the combination, compared with 8% (95% CI 3-12) in the placebo group. Although the treatment combination of Zyban and NTS displayed the highest rates of continuous abstinence throughout the study, the quit rates for the combination were not significantly higher (P>0.05) than for Zyban alone.
The comparisons between Zyban, NTS, and combination treatment in this study have not been replicated, and, therefore should not be interpreted as demonstrating the superiority of any of the active treatment arms over any other.
The third study was a long-term maintenance trial conducted at 5 clinical centers. Patients in this study received open-label Zyban 300 mg/day for 7 weeks. Patients who quit smoking while receiving Zyban (n = 432) were then randomized to Zyban 300 mg/day or placebo for a total study duration of 1 year. Abstinence from smoking was determined by patient self-report and verified by expired air carbon monoxide levels. This trial demonstrated that at 6 months, continuous abstinence rates were significantly higher for patients continuing to receive Zyban than for those switched to placebo (P<0.05; 55% versus 44%).
Quit rates in clinical trials are influenced by the population selected. Quit rates in an unselected population may be lower than the above rates. Quit rates for Zyban were similar in patients with and without prior quit attempts using nicotine replacement therapy.
Treatment with Zyban reduced withdrawal symptoms compared to placebo. Reductions on the following withdrawal symptoms were most pronounced: irritability, frustration, or anger; anxiety; difficulty concentrating; restlessness; and depressed mood or negative affect. Depending on the study and the measure used, treatment with Zyban showed evidence of reduction in craving for cigarettes or urge to smoke compared to placebo.
Use In Patients With Chronic Obstructive Pulmonary Disease (COPD)
Zyban was evaluated in a randomized, double-blind, comparative study of 404 patients with mild-to-moderate COPD, defined as FEV1≥35%, FEV1/FVC≤70% and a diagnosis of chronic bronchitis, emphysema and/or small airways disease. Patients aged 36 to 76 years were randomized to Zyban 300 mg/day (n = 204) or placebo (n = 200) and treated for 12 weeks. Treatment with Zyban was initiated at 150 mg/day for 3 days while the patient was still smoking and increased to 150 mg twice daily for the remaining treatment period. Abstinence from smoking was determined by patient daily diaries and verified by carbon monoxide levels in expired air. Quitters are defined as subjects who were abstinent during the last 4 weeks of treatment. Table 3 shows quit rates in the COPD Trial.
Table 3. COPD Trial: Quit Rates by Treatment Group
4-Week Abstinence Period
|
Treatment Groups
|
Placebo
(n = 200)
%
(95% CI)
|
Zyban 300 mg/day
(n = 204)
%
(95% CI)
|
|
Weeks 9 through 12
|
12%
(8-16)
|
22%a
(17-27)
|
aSignificantly different from placebo (P<0.05).
Indications and Usage for Zyban
Zyban is indicated as an aid to smoking cessation treatment.
Contraindications
Zyban is contraindicated in patients with a seizure disorder.
Zyban is contraindicated in patients treated with WELLBUTRIN (bupropion hydrochloride), the immediate-release formulation; WELLBUTRIN SR (bupropion hydrochloride), the sustained-release formulation; WELLBUTRIN XL (bupropion hydrochloride), the extended-release formulation; or any other medications that contain bupropion because the incidence of seizure is dose dependent.
Zyban is contraindicated in patients with a current or prior diagnosis of bulimia or anorexia nervosa because of a higher incidence of seizures noted in patients treated for bulimia with the immediate-release formulation of bupropion.
Zyban is contraindicated in patients undergoing abrupt discontinuation of alcohol or sedatives (including benzodiazepines).
The concurrent administration of Zyban and a monoamine oxidase (MAO) inhibitor is contraindicated. At least 14 days should elapse between discontinuation of an MAO inhibitor and initiation of treatment with Zyban.
Zyban is contraindicated in patients who have shown an allergic response to bupropion or the other ingredients that make up Zyban.
Warnings
Neuropsychiatric Symptoms and Suicide Risk in Smoking Cessation Treatment
Serious neuropsychiatric symptoms have been reported in patients taking Zyban for smoking cessation (see BOXED WARNING, ADVERSE REACTIONS). These have included changes in mood (including depression and mania), psychosis, hallucinations, paranoia, delusions, homicidal ideation, hostility, agitation, aggression, anxiety, and panic, as well as suicidal ideation, suicide attempt, and completed suicide. Some reported cases may have been complicated by the symptoms of nicotine withdrawal in patients who stopped smoking. Depressed mood may be a symptom of nicotine withdrawal. Depression, rarely including suicidal ideation, has been reported in smokers undergoing a smoking cessation attempt without medication. However, some of these symptoms have occurred in patients taking Zyban who continued to smoke. When symptoms were reported, most were during treatment with Zyban, but some were following discontinuation of treatment with Zyban.
These events have occurred in patients with and without pre-existing psychiatric disease; some patients have experienced worsening of their psychiatric illnesses. All patients being treated with Zyban should be observed for neuropsychiatric symptoms or worsening of pre-existing psychiatric illness.
Patients with serious psychiatric illness such as schizophrenia, bipolar disorder, and major depressive disorder did not participate in the premarketing studies of Zyban.
Advise patients and caregivers that the patient should stop taking Zyban and contact a healthcare provider immediately if agitation, depressed mood, or changes in behavior or thinking that are not typical for the patient are observed, or if the patient develops suicidal ideation or suicidal behavior. In many postmarketing cases, resolution of symptoms after discontinuation of Zyban was reported, although in some cases the symptoms persisted, therefore, ongoing monitoring and supportive care should be provided until symptoms resolve.
The risks of Zyban should be weighed against the benefits of its use. Zyban has been demonstrated to increase the likelihood of abstinence from smoking for as long as six months compared to treatment with placebo. The health benefits of quitting smoking are immediate and substantial.
Clinical Worsening and Suicide Risk in Treating Psychiatric Disorders
Patients with major depressive disorder (MDD), both adult and pediatric, may experience worsening of their depression and/or the emergence of suicidal ideation and behavior (suicidality) or unusual changes in behavior, whether or not they are taking antidepressant medications, and this risk may persist until significant remission occurs. Suicide is a known risk of depression and certain other psychiatric disorders, and these disorders themselves are the strongest predictors of suicide. There has been a long-standing concern, however, that antidepressants may have a role in inducing worsening of depression and the emergence of suicidality in certain patients during the early phases of treatment. Pooled analyses of short-term placebo-controlled trials of antidepressant drugs (SSRIs and others) showed that these drugs increase the risk of suicidal thinking and behavior (suicidality) in children, adolescents, and young adults (ages 18-24) with major depressive disorder (MDD) and other psychiatric disorders. Short-term studies did not show an increase in the risk of suicidality with antidepressants compared to placebo in adults beyond age 24; there was a reduction with antidepressants compared to placebo in adults aged 65 and older.
The pooled analyses of placebo-controlled trials in children and adolescents with MDD, obsessive compulsive disorder (OCD), or other psychiatric disorders included a total of 24 short-term trials of 9 antidepressant drugs in over 4,400 patients. The pooled analyses of placebo-controlled trials in adults with MDD or other psychiatric disorders included a total of 295 short-term trials (median duration of 2 months) of 11 antidepressant drugs in over 77,000 patients. There was considerable variation in risk of suicidality among drugs, but a tendency toward an increase in the younger patients for almost all drugs studied. There were differences in absolute risk of suicidality across the different indications, with the highest incidence in MDD. The risk differences (drug vs. placebo), however, were relatively stable within age strata and across indications. These risk differences (drug-placebo difference in the number of cases of suicidality per 1,000 patients treated) are provided in Table 4.
Table 4.
Age Range
|
Drug-Placebo Difference in Number of Cases of Suicidality per 1,000 Patients Treated
|
Increases Compared to Placebo
|
<18
|
14 additional cases
|
18-24
|
5 additional cases
|
Decreases Compared to Placebo
|
25-64
|
1 fewer case
|
≥65
|
6 fewer cases
|
No suicides occurred in any of the pediatric trials. There were suicides in the adult trials, but the number was not sufficient to reach any conclusion about drug effect on suicide.
It is unknown whether the suicidality risk extends to longer-term use, i.e., beyond several months. However, there is substantial evidence from placebo-controlled maintenance trials in adults with depression that the use of antidepressants can delay the recurrence of depression.
All patients being treated with antidepressants for any indication should be monitored appropriately and observed closely for clinical worsening, suicidality, and unusual changes in behavior, especially during the initial few months of a course of drug therapy, or at times of dose changes, either increases or decreases.
The following symptoms, anxiety, agitation, panic attacks, insomnia, irritability, hostility, aggressiveness, impulsivity, akathisia (psychomotor restlessness), hypomania, and mania, have been reported in adult and pediatric patients being treated with antidepressants for major depressive disorder as well as for other indications, both psychiatric and nonpsychiatric. Although a causal link between the emergence of such symptoms and either the worsening of depression and/or the emergence of suicidal impulses has not been established, there is concern that such symptoms may represent precursors to emerging suicidality.
Consideration should be given to changing the therapeutic regimen, including possibly discontinuing the medication, in patients whose depression is persistently worse, or who are experiencing emergent suicidality or symptoms that might be precursors to worsening depression or suicidality, especially if these symptoms are severe, abrupt in onset, or were not part of the patient's presenting symptoms.
Families and caregivers of patients being treated with antidepressants for major depressive disorder or other indications, both psychiatric and nonpsychiatric, should be alerted about the need to monitor patients for the emergence of agitation, irritability, unusual changes in behavior, and the other symptoms described above, as well as the emergence of suicidality, and to report such symptoms immediately to healthcare providers. Such monitoring should include daily observation by families and caregivers. Prescriptions for Zyban should be written for the smallest quantity of tablets consistent with good patient management, in order to reduce the risk of overdose.
Screening Patients for Bipolar Disorder
A major depressive episode may be the initial presentation of bipolar disorder. It is generally believed (though not established in controlled trials) that treating such an episode with an antidepressant alone may increase the likelihood of precipitation of a mixed/manic episode in patients at risk for bipolar disorder. Whether any of the symptoms described above represent such a conversion is unknown. However, prior to initiating treatment with an antidepressant, patients with depressive symptoms should be adequately screened to determine if they are at risk for bipolar disorder; such screening should include a detailed psychiatric history, including a family history of suicide, bipolar disorder, and depression. It should be noted that Zyban is not approved for use in treating bipolar depression.
Bupropion-Containing Products
Patients should be made aware that Zyban contains the same active ingredient found in WELLBUTRIN, WELLBUTRIN SR, and WELLBUTRIN XL used to treat depression, and that Zyban should not be used in combination with WELLBUTRIN (bupropion hydrochloride), the immediate-release formulation; WELLBUTRIN SR (bupropion hydrochloride), the sustained-release formulation; WELLBUTRIN XL (bupropion hydrochloride), the extended-release formulation; or any other medications that contain bupropion.
Seizures
Because the use of bupropion is associated with a dose-dependent risk of seizures, clinicians should not prescribe doses over 300 mg/day for smoking cessation. The risk of seizures is also related to patient factors, clinical situation, and concomitant medications, which must be considered in selection of patients for therapy with Zyban. Zyban should be discontinued and not restarted in patients who experience a seizure while on treatment.
- Dose: For smoking cessation, doses above 300 mg/day should not be used. The seizure rate associated with doses of sustained-release bupropion up to 300 mg/day is approximately 0.1% (1/1,000). This incidence was prospectively determined during an 8-week treatment exposure in approximately 3,100 depressed patients.
Data for the immediate-release formulation of bupropion revealed a seizure incidence of approximately 0.4% (4/1,000) in depressed patients treated at doses in a range of 300 to 450 mg/day. In addition, the estimated seizure incidence increases almost tenfold between 450 and 600 mg/day.
- Patient factors: Predisposing factors that may increase the risk of seizure with bupropion use include history of head trauma or prior seizure, central nervous system (CNS) tumor, the presence of severe hepatic cirrhosis, and concomitant medications that lower seizure threshold.
- Clinical situations: Circumstances associated with an increased seizure risk include, among others, excessive use of alcohol or sedatives (including benzodiazepines); addiction to opiates, cocaine, or stimulants; use of over-the-counter stimulants and anorectics; and diabetes treated with oral hypoglycemics or insulin.
- Concomitant medications: Many medications (e.g., antipsychotics, antidepressants, theophylline, systemic steroids) are known to lower seizure threshold.
Recommendations for Reducing the Risk of Seizure: Retrospective analysis of clinical experience gained during the development of bupropion suggests that the risk of seizure may be minimized if
- the total daily dose of Zyban does not exceed 300 mg (the maximum recommended dose for smoking cessation), and
- the recommended daily dose for most patients (300 mg/day) is administered in divided doses (150 mg twice daily).
- No single dose should exceed 150 mg to avoid high peak concentrations of bupropion and/or its metabolites.
Zyban should be administered with extreme caution to patients with a history of seizure, cranial trauma, or other predisposition(s) toward seizure, or patients treated with other agents (e.g., antipsychotics, antidepressants, theophylline, systemic steroids, etc.) that lower seizure threshold.
Hepatic Impairment
Zyban should be used with extreme caution in patients with severe hepatic cirrhosis. In these patients a reduced frequency of dosing is required, as peak bupropion levels are substantially increased and accumulation is likely to occur in such patients to a greater extent than usual. The dose should not exceed 150 mg every other day in these patients (see CLINICAL PHARMACOLOGY, PRECAUTIONS, and DOSAGE AND ADMINISTRATION).
Potential for Hepatotoxicity
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.
Precautions
General
Allergic Reactions: Anaphylactoid/anaphylactic reactions characterized by symptoms such as pruritus, urticaria, angioedema, and dyspnea requiring medical treatment have been reported at a rate of about 1 to 3 per thousand in clinical trials of Zyban. In addition, there have been rare spontaneous postmarketing reports of erythema multiforme, Stevens-Johnson syndrome, and anaphylactic shock associated with bupropion. A patient should stop taking Zyban and consult a doctor if experiencing allergic or anaphylactoid/anaphylactic reactions (e.g., skin rash, pruritus, hives, chest pain, edema, and shortness of breath) during treatment.
Arthralgia, myalgia, and fever with rash and other symptoms suggestive of delayed hypersensitivity have been reported in association with bupropion. These symptoms may resemble serum sickness.
Insomnia: In the dose-response smoking cessation trial, 29% of patients treated with 150 mg/day of Zyban and 35% of patients treated with 300 mg/day of Zyban experienced insomnia, compared to 21% of placebo-treated patients. Symptoms were sufficiently severe to require discontinuation of treatment in 0.6% of patients treated with Zyban and none of the patients treated with placebo.
In the comparative trial, 40% of the patients treated with 300 mg/day of Zyban, 28% of the patients treated with 21 mg/day of NTS, and 45% of the patients treated with the combination of Zyban and NTS experienced insomnia compared to 18% of placebo-treated patients. Symptoms were sufficiently severe to require discontinuation of treatment in 0.8% of patients treated with Zyban and none of the patients in the other 3 treatment groups.
Insomnia may be minimized by avoiding bedtime doses and, if necessary, reduction in dose.
Psychosis, Confusion, and Other Neuropsychiatric Phenomena: Depressed patients treated with bupropion in depression trials have been reported to show a variety of neuropsychiatric signs and symptoms including delusions, hallucinations, psychosis, concentration disturbance, paranoia, and confusion. In some cases, these symptoms abated upon dose reduction and/or withdrawal of treatment. In clinical trials with Zyban conducted in nondepressed smokers, the incidence of neuropsychiatric side effects was generally comparable to placebo. However, in the postmarketing experience, patients taking Zyban to quit smoking have reported similar types of neuropsychiatric symptoms to those reported by patients in the clinical trials of bupropion for depression.
Activation of Psychosis and/or Mania: Antidepressants can precipitate manic episodes in bipolar disorder patients during the depressed phase of their illness and may activate latent psychosis in other susceptible individuals. The sustained-release formulation of bupropion is expected to pose similar risks. There were no reports of activation of psychosis or mania in clinical trials with Zyban conducted in nondepressed smokers.
Cardiovascular Effects: In clinical practice, hypertension, in some cases severe, requiring acute treatment, has been reported in patients receiving bupropion alone and in combination with nicotine replacement therapy. These events have been observed in both patients with and without evidence of preexisting hypertension.
Data from a comparative study of Zyban, nicotine transdermal system (NTS), the combination of sustained-release bupropion plus NTS, and placebo as an aid to smoking cessation suggest a higher incidence of treatment-emergent hypertension in patients treated with the combination of Zyban and NTS. In this study, 6.1% of patients treated with the combination of Zyban and NTS had treatment-emergent hypertension compared to 2.5%, 1.6%, and 3.1% of patients treated with Zyban, NTS, and placebo, respectively. The majority of these patients had evidence of preexisting hypertension. Three patients (1.2%) treated with the combination of Zyban and NTS and 1 patient (0.4%) treated with NTS had study medication discontinued due to hypertension compared to none of the patients treated with Zyban or placebo. Monitoring of blood pressure is recommended in patients who receive the combination of bupropion and nicotine replacement.
There is no clinical experience establishing the safety of Zyban in patients with a recent history of myocardial infarction or unstable heart disease. Therefore, care should be exercised if it is used in these groups. Bupropion was well tolerated in depressed patients who had previously developed orthostatic hypotension while receiving tricyclic antidepressants, and was also generally well tolerated in a group of 36 depressed inpatients with stable congestive heart failure (CHF). However, bupropion was associated with a rise in supine blood pres
