Products
Varenicline is commercially available in the form of film-coated tablets (Champix, in some countries: Chantix). It has been approved in many countries since 2006 and has been reimbursable under certain conditions since July 1, 2013. Full reimbursement details can be found in the Specialty List under Limitations.
Structure and properties
Varenicline (C13H13N3, Mr = 211.3 g/mol) is present in the drug as varenicline tartrate, a white to slightly yellow powder that is very soluble in water. It is a derivative of the quinolizidine alkaloid cytisine, which occurs in laburnum, a poisonous ornamental plant found in many gardens.
Effects
Varenicline (ATC N07BA03) has weaning properties. The effects are due to selective partial agonism at the nicotinic acetylcholine receptor α4β2, preventing the binding of nicotine and the associated reward and reinforcement. Partial agonism means that varenicline acts as both an agonist and antagonist at the receptor. Agonism attenuates smoking cravings and withdrawal symptoms, and antagonism prevents the rewarding and reinforcing effects of smoking. Varenicline has a long half-life of up to 24 hours.
Indications
For smoking cessation in adults.
Dosage
According to the Smoking Guide. Treatment is started gradually with an initial pack one to two weeks before smoking cessation. Subsequently, one tablet is taken twice daily, independent of meals. The recommended duration of therapy is three months. If smoking cessation is successful, the drug should be taken for an additional three months.
Contraindications
- Hypersensitivity
For complete precautions, see the drug label.
Interactions
Varenicline is poorly metabolized and does not interact with CYP450. It is filtered, actively secreted via the organic cation transporter OCT2, and excreted primarily in the urine. Varenicline has a profound potential for drug-drug interactions. However, smoking cessation may increase plasma concentrations of CYP1A2 substrates independent of drug intake.
Adverse effects
The most common possible adverse effects include headache, dizziness, fatigue, drowsiness, insomnia, abnormal dreams, nausea, indigestion, taste disturbances, and increased appetite. Some of these side effects may also be related to smoking cessation. Severe neuropsychiatric disorders have been reported in rare cases (e.g., behavioral changes, psychosis, depression, suicidal ideation).
