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. |
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 | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for WELLBUTRIN XL (WELLBUTRIN XL).
| Breastfeeding | Bupropion is excreted into breast milk in low amounts. The average infant relative dose (RID) is approximately 2% of the maternal weight-adjusted dose, which is below the 10% threshold considered safe. The milk-to-plasma (M/P) ratio is estimated to be about 0.33. Adverse effects in breastfed infants are rare but include possible irritability, poor feeding, and seizures. Caution is advised, especially in preterm or compromised infants. Monitoring for adverse effects is recommended. |
| 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. |
■ 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 disorder; eating disorder (anorexia/bulimia); abrupt discontinuation of alcohol, benzodiazepines, barbiturates, antiepileptics; MAOI use within 14 days.
| Precautions | Seizure risk; neuropsychiatric reactions; hypertension; activation of mania/hypomania; hepatotoxicity; angle-closure glaucoma. |
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| 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. |