Varenicline is a prescription medication used to treat smoking addiction.
It is marketed by Pfizer, usually in the form of varenicline tartrate [trade name Chantix in the USA and Champix in Canada, Europe and other countries].
Mechanism of Action
Varenicline is a nicotinic receptor partial agonist. That means it stimulates the same receptors which nicotine does, though the stimulation is not as strong.
When used it does two effects
- Reduces cravings
- Decreases the pleasurable effects of cigarettes and other tobacco products.
Varenicline is a partial agonist of the α4β2 subtype of the nicotinic acetylcholine receptor. In addition it acts on α3β4 and weakly on α3β2 and α6-containing receptors. A full agonism was displayed on α7-receptors.
Due to its competitive binding on these receptors, varenicline blocks the ability of nicotine to bind and stimulate the mesolimbic dopamine system.
Varenicline also acts as an agonist at 5-HT3 receptors, which may contribute to mood altering effects of varenicline.
About 90 percent of the active compound is excreted renally. Rest of it is excreted after conjugation.
The elimination half-life is about 24 hours.
Varenicline is indicated for smoking cessation.
It is given for twelve weeks and if smoking cessation does not occur ,it may be continued for another twelve weeks.
Varenicline has not been tested in those under 18 years old or pregnant women and therefore is not recommended for use by these groups.
Following side effects are noted with use of varenicline.
- Common -Nausea
- Less common – Headache, difficulty in sleeping, abnormal dreams.
- Rare – change in taste, vomiting, abdominal pain, flatulence, and constipation.
- Some patients have reported changes in behavior, agitation, depressed mood, suicidal thoughts or actions.
- Recently alert by FDA alerted about a small, increased risk of certain cardiovascular adverse events in patients who have cardiovascular disease.