WELLBUTRIN XL
Clinical safety rating: caution
Comprehensive clinical and safety monograph for WELLBUTRIN XL (WELLBUTRIN XL).
Bupropion is a dopamine and norepinephrine reuptake inhibitor; its mechanism in smoking cessation is unknown.
| Metabolism | Hepatic via CYP2B6; major metabolites: hydroxybupropion, threohydrobupropion, erythrohydrobupropion. |
| Excretion | Renal (87% as metabolites, 0.5% as parent drug) and fecal (10%). |
| Half-life | 21 ± 9 hours (terminal half-life of bupropion); clinical context: steady-state reached in 5-6 days. |
| Protein binding | 82-88% bound to albumin. |
| Volume of Distribution | 20-70 L/kg (mean 27 L/kg); clinical meaning: extensive tissue distribution. |
| Bioavailability | Oral: 5-20% (due to extensive first-pass metabolism). |
| Onset of Action | Oral: antidepressive effect may begin in 1-2 weeks, full effect by 4-6 weeks. |
| Duration of Action | 24 hours (sustained release); clinical notes: once-daily dosing for XL formulation. |
| Molecular Weight | 239.74 |
150 mg orally once daily; may increase to 300 mg once daily after 4 days, with maximum 300 mg/day.
| Dosage form | TABLET, EXTENDED RELEASE |
| Renal impairment | CrCl < 30 mL/min: Not recommended; if used, extend dosing interval and reduce dose by 50%. |
| Liver impairment | Child-Pugh Class A (mild): 75 mg once daily; Class B (moderate): 50 mg once daily; Class C (severe): Contraindicated. |
| Pediatric use | Not FDA-approved for patients < 18 years; off-label use in adolescents: 150 mg once daily, max 300 mg/day. |
| Geriatric use | Start at 100 mg once daily; increase by 50-100 mg every 3-4 days; maximum 300 mg/day; monitor for hypertension and agitation. |
| 1st trimester | Bupropion has been associated with increased risk of cardiovascular malformations, particularly ventricular septal defects, when used in the first trimester. Some studies show a small increased risk of spontaneous abortion. Use only if potential benefit outweighs risk. |
| 2nd trimester | Limited data suggest possible risks of preterm birth and low birth weight. May be considered if necessary, but avoid prolonged use. |
| 3rd trimester | May increase risk of neonatal withdrawal syndrome, including irritability, poor feeding, and respiratory depression. Use with caution; consider gradual tapering near term. |
Clinical note
Comprehensive clinical and safety monograph for WELLBUTRIN XL (WELLBUTRIN XL).
| Placental transfer | Bupropion crosses the placenta. Hydroxybupropion (active metabolite) accumulates in fetal plasma with cord-to-maternal plasma ratio of 0.5 to 1.5. |
| Breastfeeding | Bupropion is excreted into breast milk in small amounts. Estimated relative infant dose is 2% of maternal weight-adjusted dose. One case report of seizure in a nursing infant. Consider risk of neonatal seizures; use with caution in breastfeeding women, especially if infant has risk factors for seizures. |
■ FDA Black Box Warning
Increased risk of suicidal thinking and behavior in children, adolescents, and young adults with major depressive disorder and other psychiatric disorders.
| Serious Effects |
Seizure disorderCurrent or prior diagnosis of bulimia or anorexia nervosaAcute abrupt discontinuation of alcohol, benzodiazepines, or sedativesUse of MAOIs within 14 daysKnown hypersensitivity to bupropion
| Precautions | Seizure risk; neuropsychiatric reactions; hypertension; activation of mania/hypomania; hepatotoxicity; angle-closure glaucoma. |
| Food/Dietary | Take with or without food. Avoid large amounts of high-fat meals as they may increase the rate of absorption. No specific food restrictions, but grapefruit and grapefruit juice should be avoided due to potential CYP450 interactions (though bupropion is primarily metabolized by CYP2B6, caution is advised). |
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| Lactation Rating | L3 (Moderately Safe) |
| Teratogenic Risk | Bupropion (Wellbutrin XL) is not a major teratogen. Studies have not shown a significantly increased risk of major congenital malformations overall; however, some data suggest a possible small increased risk of cardiovascular malformations, particularly ventricular septal defects (VSD), with first-trimester exposure. The absolute risk is low. Third-trimester exposure may be associated with mild neonatal withdrawal symptoms including irritability, feeding difficulties, and respiratory distress. |
| Fetal Monitoring | Monitor maternal blood pressure and heart rate regularly as bupropion may cause hypertension and tachycardia. For fetal well-being, standard prenatal monitoring including fetal growth assessments and ultrasound as clinically indicated. Neonates should be monitored for signs of withdrawal (e.g., irritability, poor feeding, respiratory distress) if exposed in the third trimester. |
| Fertility Effects | Bupropion has no known significant adverse effects on fertility in humans. Animal studies have shown no impairment of fertility at doses up to 7 times the maximum recommended human dose. However, hyperprolactinemia and galactorrhea have been reported rarely, which could theoretically affect fertility. The overall risk is low. |
| Clinical Pearls | Wellbutrin XL (bupropion HCl extended-release) is activating and may worsen anxiety; avoid in patients with seizure disorder or history of seizures, eating disorders, or abrupt discontinuation of alcohol, benzodiazepines, or antiseizure drugs. Maximum dose 450 mg/day (300 mg/day for XL formulation) to reduce seizure risk. Monitor for hypertension, especially when used with nicotine replacement therapy. May cause false positive urine amphetamine screens. |
| Patient Advice | Take exactly as prescribed; do not crush, chew, or split the XL tablets. · Avoid alcohol consumption while taking this medication. · Report any rash, hives, or swelling of the face/mouth immediately. · May cause insomnia; take in the morning to minimize sleep disturbances. · Do not stop abruptly; taper under medical supervision to avoid withdrawal symptoms. · May cause dry mouth; sip water or use sugarless gum. · Contact your doctor if you experience new or worsening depression, suicidal thoughts, or behavioral changes. · Avoid driving until you know how this medication affects you, as it may cause dizziness. · Inform all healthcare providers you are taking this medication, especially before surgery or drug testing. |