The main factor affecting varenicline dose is the stage the patient is at in treatment. Varenicline is used as an aid for stopping smoking and is started at a low dose and worked up over several days. Another factor which may affect the varenicline dose is renal dysfunction, which may necessitate a lower dose. In most countries, varenicline is available by prescription only through a doctor and it may be known by different trade names, according to manufacturer in different countries.
Varenicline works to help stopping smoking by two main mechanisms. Primarily, it stimulates the nicotinic receptors in the brain, which are the same receptors that nicotine from cigarette smoking acts on, and therefore reduces the craving and withdrawal symptoms. It also blocks the nicotine and stops it from acting on the receptors so that the pleasure normally derived from smoking no longer occurs.
When prescribing varenicline, the doctor will counsel the patient carefully. They should establish a date on which smoking will be stopped and the first varenicline dose is taken a week or two before this date. The initial varenicline dose is usually 0.5 mg once a day, increasing after three days to 0.5 mg twice a day. After seven days of treatment the varenicline dose is increased to 1 mg twice daily. This is continued for 12 weeks, with a second course sometimes being prescribed to increase the chance of long-term abstinence from smoking.
As with any medication, varenicline may cause adverse effects in some patients. Side effects that have been reported included nausea, headache, insomnia, strange dreams and dizziness, gastrointestinal side effects and psychiatric side effects. It is best to avoid driving and the operation of heavy machinery, especially while initiating treatment with varenicline. Should side effects occur, medical advice should be sought and the treatment may be stopped or a lower varenicline dose may be given.
When starting varenicline it is important that the prescribing doctor is informed of any other medications the person is taking, as interactions may occur. This includes homeopathic, complementary and over-the-counter products. The dose of other medications may also be affected by smoking so upon the discontinuation of smoking, dosages of these may need to be adjusted in order to maintiain therapeutic control. Treatment with varenicline may be contraindicated in patients with some underlying conditions so these, too should be discussed with the doctor, as should pregnancy, desired pregnancy and lactation.