VARENICLINE
Clinical safety rating: safe
Animal studies have demonstrated safety
Partial agonist at α4β2 nicotinic acetylcholine receptors; full agonist at α7 nicotinic receptors. Reduces nicotine craving and withdrawal symptoms by binding to receptors and blocking nicotine binding.
| Metabolism | Metabolized primarily by glucuronidation via UGT2B7 and oxidation via CYP2A6 (minor). Minimal metabolism; 92% excreted unchanged in urine. |
| Excretion | Renal: 92% unchanged in urine; fecal: <2%; hepatic metabolism: minimal. |
| Half-life | Terminal elimination half-life: 24 hours; steady-state reached within 4 days. |
| Protein binding | Low: <20%; primarily to albumin. |
| Volume of Distribution | Vd: 6.6 L/kg; indicates extensive tissue distribution. |
| Bioavailability | Oral: >90% absorbed. |
| Onset of Action | Oral: 2-3 days for initial reduction in craving; full effect by 4 weeks. |
| Duration of Action | Oral: 12 weeks for smoking cessation; may extend to 24 weeks for prevention. |
| Molecular Weight | 271.35 |
1 mg orally twice daily after 1-week titration: 0.5 mg once daily for days 1-3, 0.5 mg twice daily for days 4-7, then 1 mg twice daily. Reduce to 0.5 mg twice daily if intolerance.
| Dosage form | TABLET |
| Renal impairment | CrCl < 30 mL/min: maximum 0.5 mg twice daily; CrCl < 15 mL/min or hemodialysis: not recommended. |
| Liver impairment | No dose adjustment required for mild-to-moderate hepatic impairment (Child-Pugh A or B). Not studied in severe hepatic impairment (Child-Pugh C); use with caution. |
| Pediatric use | Safety and efficacy not established in patients <18 years. Not approved for pediatric use. |
| Geriatric use | No routine dose adjustment based on age alone; consider renal function. Elderly patients may be more sensitive to adverse effects (e.g., nausea, insomnia). |
| 1st trimester | Contraindicated due to risk of fetal harm; animal studies show decreased fetal weight and increased offspring variations. |
| 2nd trimester | Contraindicated; limited human data but potential for fetal harm outweighs benefits. |
| 3rd trimester | Contraindicated; may cause fetal nicotine withdrawal-like symptoms and potential neurobehavioral effects. |
Clinical note
No significant drug interactions Can cause serious neuropsychiatric events including depression and suicidal thoughts.
| Placental transfer | Varenicline crosses the placenta in animals; human data not available but expected due to molecular weight <500 Da and lipophilicity. |
| Breastfeeding | Not recommended during breastfeeding. Varenicline is excreted in animal milk; no human data available. Potential for adverse effects in nursing infants due to high lipophilicity and long half-life. |
■ FDA Black Box Warning
Serious neuropsychiatric events including suicidal thoughts/behavior, hostility, agitation, depressed mood, and unusual changes in behavior have been reported. Risk is increased in patients with psychiatric disorders at baseline.
| Common Effects | Nausea |
| Serious Effects |
Hypersensitivity to varenicline or any componentEnd-stage renal disease on dialysis (use not recommended)
| Precautions | Neuropsychiatric symptoms: monitor for changes in mood/behavior, Cardiovascular events: increased risk of myocardial infarction and stroke in patients with cardiovascular disease, Angioedema and hypersensitivity reactions, Seizures: increased risk in patients with history of seizures, Interaction with alcohol: may increase alcohol effects |
| Food/Dietary | No significant food interactions. Taking after meals with a full glass of water reduces nausea. |
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| Lactation Rating | L5 - Contraindicated |
| Teratogenic Risk | Pregnancy Category C. First trimester: Limited human data; animal studies show reduced fetal weight and skeletal variations at supratherapeutic doses. Second/third trimester: No controlled studies; potential risk of nicotinic acetylcholine receptor modulation affecting fetal neurodevelopment. |
| Fetal Monitoring | Monitor maternal blood pressure and heart rate due to potential cardiovascular effects. Assess for nausea, vomiting, and neuropsychiatric symptoms. No specific fetal monitoring required but consider growth ultrasound if exposure during pregnancy. |
| Fertility Effects | No human data. Animal studies show no impairment of fertility at clinically relevant doses. Potential for reduced spermatogenesis at high doses in male rats; relevance unknown. |
| Clinical Pearls | Titrate dose over first week (0.5 mg daily for 3 days, then 0.5 mg BID for 4 days, then 1 mg BID). Reduce dose in severe renal impairment (CrCl <30 mL/min): start 0.5 mg daily, may increase to 0.5 mg BID. Avoid coadministration with nicotine replacement therapy (NRT) due to increased adverse effects (nausea, headache). Monitor for neuropsychiatric symptoms (suicidality, hostility, depression), especially in patients with history of psychiatric illness. Efficacy improves if patient sets a target quit date (TQD) between days 8-14 of treatment. Do not use in patients with end-stage renal disease (ESRD) on dialysis. |
| Patient Advice | Set a quit date (target date to stop smoking) for around day 8 to 14 of medication use. · Take the pills after eating with a full glass of water to reduce nausea. · Do not take a double dose if you miss a dose; skip it and take next at normal time. · Possible side effects: nausea (common), vivid dreams, headache, constipation, gas, insomnia. · If you experience any unusual changes in mood, behavior, or thoughts of suicide, stop the medicine and call your doctor immediately. · Do not smoke while taking this medicine; it may increase side effects. |