Adult: 0.5 mg once daily for Days 1-3, increased to 0.5 mg bid for Days 4-7. Maintenance (Day 8 up to end of treatment): 1 mg bid for 11 weeks; may reduce temporarily or permanently to 0.5 mg bid if adverse effects are intolerable. Usual treatment duration: 12 weeks. Patient must set a date to stop smoking, then start dosing 1-2 weeks prior to the target stop date. Alternatively, may begin dosing then quit smoking between Days 8-35 of treatment. In patients who successfully quit smoking at the end of 12 weeks: May consider additional treatment course of 12 weeks at 1 mg bid to reduce the risk of relapse. In patients who did not succeed or who relapsed after previous therapy: May consider a 2nd course of treatment after addressing factors that contributed to the failure of initial treatment. Gradual approach may be considered in patients who are not able or willing to quit abruptly by starting varenicline dosing and reducing smoking by 50% from baseline within the 1st 4 weeks, then an additional 50% reduction in the next 4 weeks; continue reducing to reach complete abstinence by 12 weeks.
Renal Impairment
ESRD undergoing haemodialysis: Max: 0.5 mg once daily, if tolerated.
CrCl (mL/min)
Dosage
<30
0.5 mg once daily for the 1st 3 days, increased to Max of 0.5 mg bid or 1 mg once daily, as necessary.
30-50
In patients who have intolerable adverse effects: 1 mg once daily.
Contraindications
Hypersensitivity.
Special Precautions
Patient with history of psychiatric illness, history of seizure or other conditions that may lower seizure threshold; CV disease. Renal impairment. Pregnancy and lactation.
Adverse Reactions
Significant: Serious neuropsychiatric events (e.g. anxiety, psychosis, aggression, mood swings, agitation, hostility, hallucinations, paranoia, delusion, suicidal thoughts or behaviour, suicide attempt), exacerbation of underlying psychiatric condition (e.g. depression), somnambulism, CNS depression, seizures; transient or persistent nausea (dose-dependent); increased risk of CV events (e.g. MI, stroke). Cardiac disorders: Chest pain. Gastrointestinal disorders: Abdominal pain or distension, vomiting, diarrhoea, constipation, flatulence, dyspepsia, dry mouth, toothache, GERD, dysgeusia. General disorders and administration site conditions: Fatigue. Investigations: Increased weight, abnormal LFTs. Metabolism and nutrition disorders: Increased or decreased appetite. Musculoskeletal and connective tissue disorders: Back pain, arthralgia, myalgia. Nervous system disorders: Headache, dizziness, somnolence. Psychiatric disorders: Insomnia, abnormal dreams. Respiratory, thoracic and mediastinal disorders: Dyspnoea, cough, nasopharyngitis, sinusitis, bronchitis. Skin and subcutaneous tissue disorders: Rash, pruritus. Potentially Fatal: Hypersensitivity reaction, including angioedema. Rarely, serious skin reactions (e.g. Stevens-Johnson syndrome, erythema multiforme).
This drug may cause dizziness, somnolence, difficulty in concentrating, or transient loss of consciousness; if affected, do not drive or operate machinery.
Monitoring Parameters
Obtain renal function tests and electrolyte. Monitor for changes in behaviour and psychiatric symptoms (e.g. depression, hostility, agitation, suicidal ideation or behaviour). Give counselling and educational materials to support the attempt on quitting smoking. Assess the progress on smoking cessation following 12 weeks.
Drug Interactions
Increased incidence of adverse effects (e.g. headaches, dizziness, nausea, vomiting, dyspepsia, fatigue) with transdermal nicotine. Increased systemic exposure with cimetidine. Effects of smoking cessation may alter the pharmacodynamics or pharmacokinetics of some agents (e.g. warfarin, theophylline, insulin); dose adjustment may be needed.
Food Interaction
May increase the adverse effects of alcohol.
Action
Description: Varenicline is a highly selective and potent partial α4β2 nicotinic acetylcholine receptor agonist. It acts by preventing nicotine stimulation of the mesolimbic dopamine system, the neuronal mechanism underlying reward and reinforcement experienced during smoking. Additionally, it stimulates dopamine activity but to a much lesser extent than nicotine, leading to reduced craving and withdrawal symptoms. Pharmacokinetics: Absorption: Well absorbed from the gastrointestinal tract. Bioavailability: Approx 90%. Time to peak plasma concentration: Approx 3-4 hours. Distribution: Distributed into tissues, including the brain. Plasma protein binding: ≤20%. Metabolism: Minimal metabolism. Excretion: Via urine (approx 92% as unchanged drug, <10% as metabolites). Elimination half-life: Approx 24 hours.
Chemical Structure
Varenicline Source: National Center for Biotechnology Information. PubChem Compound Summary for CID 170361, Varenicline. https://pubchem.ncbi.nlm.nih.gov/compound/Varenicline. Accessed June 24, 2021.
N07BA03 - varenicline ; Belongs to the class of drugs used in the management of nicotine dependence.
References
Anon. Varenicline Tartrate. AHFS Clinical Drug Information [online]. Bethesda, MD. American Society of Health-System Pharmacists, Inc. https://www.ahfscdi.com. Accessed 01/06/2021.Anon. Varenicline. Lexicomp Online. Hudson, Ohio. Wolters Kluwer Clinical Drug Information, Inc. https://online.lexi.com. Accessed 01/06/2021.Buckingham R (ed). Varenicline. Martindale: The Complete Drug Reference [online]. London. Pharmaceutical Press. https://www.medicinescomplete.com. Accessed 01/06/2021.Champix 0.5 mg and 1 mg Film-Coated Tablets (Pfizer Limited). MHRA. https://products.mhra.gov.uk. Accessed 01/06/2021.Champix 0.5 mg and 1 mg Film-Coated Tablets (Pfizer Malaysia Sdn. Bhd.). National Pharmaceutical Regulatory Agency - Ministry of Health Malaysia. https://www.npra.gov.my. Accessed 01/06/2021.Chantix Tablet, Film Coated (Pfizer Laboratories Div Pfizer Inc). DailyMed. Source: U.S. National Library of Medicine. https://dailymed.nlm.nih.gov/dailymed. Accessed 01/06/2021.Joint Formulary Committee. Varenicline. British National Formulary [online]. London. BMJ Group and Pharmaceutical Press. https://www.medicinescomplete.com. Accessed 01/06/2021.
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