Varenicline

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[edit] BRAND NAMES

[edit] STRUCTURE

Varenicline.jpg

[edit] MECHANISM OF ACTION

People who smoke become addicted to nicotine, a chemical in tobacco. Nicotine acts in the nervous system, where it binds to receptors and triggers the release of a chemical messenger, dopamine, which plays a part in the pleasure derived from smoking.

Varenicline binds with high affinity and selectivity at α4β2 neuronal nicotinic acetylcholine receptors. When binding to these receptors, varenicline acts in two ways: It acts like nicotine but with lower intrinsic efficacy (partial agonist) and this helps to relieve craving symptoms, and, in the presence of nicotine, it prevents nicotine binding to these receptors (antagonist), and this helps to reduce the pleasurable effects of smoking.

[edit] INDICATIONS

Varenicline is used in adults to help them stop smoking

[edit] DOSAGE

Treatment with Varenicline is more likely to succeed in smokers who are motivated to stop smoking and who are also receiving additional advice and support. Patients set themselves a target date for quitting and will usually start taking Varenicline one to two weeks before this date. Patients who are unwilling or unable to set a target date within one to two weeks could be offered the treatment first and then later choose their target date to fall within five weeks of starting treatment.

Treatment with Varenicline lasts for 12 weeks. The tablets are swallowed whole with water, with or without food.

In the first week the patient takes one 0.5 mg tablet once a day for three days, followed by one 0.5 mg tablet twice a day for four days. For the remaining 11 weeks of treatment, the patient takes one 1 mg tablet twice a day. Reduced doses may be used in patients who do not tolerate the medicine or who have kidney problems

For patients who have successfully stopped smoking after 12 weeks of treatment, doctors may choose to carry on treatment for another 12 weeks

[edit] CONTRAINDICATIONS

  • Hypersensitivity to Varenicline

[edit] WARNINGS AND PRECAUTIONS

  • Neuropsychiatric Symptoms and Suicidality: Changes in behaviour or thinking, anxiety, psychosis, mood swings, aggressive behaviour, depression, suicidal ideation and behaviour and suicide attempts have been reported in patients attempting to quit smoking with Varenicline in the post-marketing experience. If any of these signs and symptoms happens, Varenicline should be discontinued immediately
  • Angioedema and hypersensitivity reactions: Such reactions, including angioedema, infrequently life threatening, have been reported. Clinical signs included swelling of the face, mouth (tongue, lips, and gums), neck (throat and larynx) and extremities. Patients should be instructed to discontinue Varenicline and immediately seek medical care if symptoms occur.
  • Serious skin reactions: Rare, potentially life-threatening skin reactions have been reported. Instruct patients to discontinue Varenicline and contact a healthcare provider immediately at first appearance of skin rash with mucosal lesions.
  • Cardiovascular events: In a trial of patients with stable cardiovascular disease (CVD) certain cardiovascular events were reported more frequently in patients treated with Varenicline. A meta-analysis of 15 clinical trials, which included the smoking cessation trial of patients with stable cardiovascular disease, had similar results. Patients taking Varenicline should be instructed to notify their doctor of new or worsening cardiovascular symptoms and to seek immediate medical attention if they experience signs and symptoms of myocardial infarction or stroke.
  • Accidental injury: Accidental injuries (e.g., traffic accidents) have been reported. Instruct patients to use caution driving or operating machinery until they know how Varenicline may affect them.
  • Seizures: In clinical trials and post-marketing experience there have been reports of seizures in patients with or without a history of seizures. Varenicline should be used cautiously in patients with a history of seizures or other conditions that potentially lower the seizure threshold.
  • Treatment discontinuation: At the end of treatment, discontinuation of Varenicline was associated with an increase in irritability, urge to smoke, depression, and/or insomnia in up to 3% of patients. The prescriber should inform the patient accordingly and discuss or consider the need for dose tapering
  • Nausea: Nausea is the most common adverse reaction (up to 30% incidence rate). Dose reduction may be helpful

[edit] INTERACTIONS

  • CYP1A2 substrates: Physiological changes resulting from smoking cessation, with or without treatment with Varenicline, may alter the pharmacokinetics or pharmacodynamics of some medicinal products, for which dosage adjustment may be necessary (examples include theophylline, warfarin and insulin). As smoking induces CYP1A2, smoking cessation may result in an increase of plasma levels of CYP1A2 substrates
  • Coadministration of varenicline and transdermal nicotine resulted in a high rate of discontinuation due to adverse events

[edit] PREGNANCY AND LACTATION

  • Pregnancy Category C (US). Varenicline should be used during pregnancy only if the potential benefit justifies the potential risk to the fetus.
  • Nursing Mothers: It is not known whether Varenicline is excreted in human milk. In animal studies varenicline was excreted in milk of lactating animals. Because many drugs are excreted in human milk and because of the potential for serious adverse reactions in nursing infants from Varenicline, a decision should be made whether to discontinue nursing or to discontinue the drug, taking into account the importance of the drug to the mother

[edit] SIDE EFFECTS

The most common side-effects with Champix (seen in more than 1 patient in 10) are nausea (feeling sick), insomnia (difficulty sleeping), abnormal dreams and headache.

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[edit] REFERENCES