Smoking Cessation Therapy
Examples
- Bupropion/Amfebutamone (Zyban)
- Varenicline (Champix)
Indications
An adjunct to motivational support in patients who want to give up smoking.
Bupropion and varenicline are second line treatments for smoking cessation; Nicotine Replacement Therapy is first line therapy.
Suitable patient selection is vital, do not expose patients who are unlikely to succeed in stopping smoking to the potential serious adverse effects of these drugs.
Contraindications
Bupropion
Contraindications
- Epilepsy
- Eating disorders
- CNS tumours
- Pregnancy
- Severe liver cirrhosis
- Alcohol/Benzodiazepine withdrawal
- Bipolar Disorder
Cautions
- Patients with predisposition to seizures, e.g. excess alcohol consumption
- Alcohol Abuse
- Elderly
Varenicline
Contraindications
Cautions
- Patients with a history of mental illness – close monitoring is required if treatment commenced
- Breast feeding (animal studies suggest excretion in breast milk; little data available)
- Predisposition to seizures
Mechanism
Bupropion is an inhibitor of the re-uptake of noradrenaline and dopamine in central monoaminergic neurons. The mechanism in which it helps smoking cessation is unknown. It is thought to be an adaptive response within the brain to changes in monoaminergic neurotransmission.
Varenicline is a partial agonist acting at the α4β2 nicotinic acetylcholine receptor. This alleviates symptoms of withdrawal and reduces the effects of smoking by preventing nicotine binding to these receptors.
Administration
Orally
NICE guidelines state that Bupropion and Varenicline should only be given to patients who commit to a specific quit date. Treatment should be started 1 to 2 weeks prior to that date.
Initially the treatment is for 3-4 weeks and is only continued if the patient is not smoking.
Adverse Reactions
Bupropion
Common
- Insomnia
- Depression
- Agitation
- Anxiety
- Drowsiness, this may interfere with driving ability
- Rash
- Headache
- Tremor
- Dizziness
- GI upset
Rare
- Seizures
- Hallucinations
- Behavioural disturbance including suicidal ideation
- Other hypersensitivity reactions including Steven- Johnson syndrome
- Hypertension
Varenicline
Common
- Nausea
- Headache
- Insomnia
- Abnormal dreams
- Dizziness
- GI disturbance
- Drowsiness
Post marketing concerns about altered mood and suicidal ideation.
Rare
- Severe cutaneous reactions including Steven-Johnson syndrome
Interactions
Do not prescribe Bupropion in combination with drugs which lower the seizure threshold.
Bupropion is an enzyme inhibitor of the CYP2D6 pathway and may affect plasma concentration of drugs metabolised in this pathway. Bupropion levels may be altered by enzyme inducers and inhibitors.
Bupropion and vareniciline should not be prescribed in combination with MAOIs.
Education
Explain to the patients that these drugs will help in smoking cessation, but it will not remove all cravings.
Inform the patient about all adverse effects, in particular the risk of seizures. Ensure the patient understands the impact a seizure may have on a person's ability to work and live.
Patients on bupropion and varenicline should be informed that should agitation, depressed mood or suicidal thoughts occur, they should discontinue treatment and medical help must be sought.
Patents should be advised that drowsiness may occur and it may affect performance tasks, for example driving.
Pharmacokinetics
Bupropion
Metabolism: reduce the dose in patients with hepatic or renal insufficiency
Varenicline
Reduce dose in moderate to severe renal insufficiency
