Varenicline (chantix) for Smoking Cessation

Varenicline (Chantix) prevents nicotine stimulation of mesolimbic dopamine system associated with nicotine addiction.

It is used in the treatment of smoking cessation.

E-Cigarettes once thought to become a good aid for the cessation of smoking, is now considered more harmful. Recently, a lot of patients have developed serious lung diseases with its use. It is also considered a gateway to addiction.

Chantix (Varenicline) Dose in Adults

Chantix (Varenicline) Dose in the treatment of Smoking cessation:

It is not available over the counter.

Initial dosage
- Days 1 - 3: 5 mg orally once a day is given
- Days 4 to 7: 5 mg orally two times a day is given
Maintenance (≥ Day 8):
- 1 mg orally two times a day for 11 weeks is given
- Consider a temporary or permanent dose reduction if the normal dose is not tolerated.
It should be started one week prior target quit date.
Patients can also consider setting a quit date up to 35 days after starting varenicline according to the manufacturer.
For patients who are not confident that they can quit abruptly, start treatment with varenicline and reduce smoking by 50% from baseline within the first 4 weeks then by an additional 50% in the next 4 weeks, and continue to reduce the goal of complete abstinence by 12 weeks.
If the patient successfully stops smoking at the end of the 12 weeks, then continue for another 12 weeks to help maintain success.
Patients who do not succeed in stopping smoking but are motivated to stop during previous therapy, or who relapse after treatment, should be encouraged to have another attempt with varenicline.

Chantix (Varenicline) Dose in Childrens

Not recommended for use in children.

Pregnancy Risk Factor: C

It is difficult to find information on the use of varenicline during pregnancy.
Negative events can be seen in both the mother's and the fetus.
All pregnant women should quit smoking.

Varenicline (Chantix) use during breastfeeding:

It is unknown if breast milk contains varenicline.
Varenicline is not recommended for breastfeeding mothers as there is insufficient information.
The manufacturer suggests that a decision be made about whether to stop breastfeeding or discontinue using the drug.
This is in consideration of the possible side effects for breastfed infants.
Breastfeeding infants should be checked for seizures and excessive vomiting.

Chantix dose in Kidney disease:

CrCl ≥30 mL/minute:
- No dosage adjustment required.
CrCl <30 mL/minute:
- Start with 0.5 mg once daily with increasing up to 0.5 mg two times a day.
End-stage renal disease (ESRD) (receiving hemodialysis):
- The maximum dose is 0.5 mg once a day

Dose in liver disease:

No dosage adjustment required.

Common Side Effects of Varenicline (Chantix) Include:

Central Nervous System:
- Headache
- Insomnia
- Abnormal Dreams
- Irritability
- Suicidal Ideation
- Depression
Gastrointestinal:
- Nausea
- Vomiting

Less Common Side Effects of Varenicline (Chantix) Include:

Cardiovascular:
- Angina Pectoris
- Chest Pain
- Peripheral Edema
- Myocardial Infarction
Central Nervous System:
- Anxiety
- Malaise
- Agitation
- Sleep Disorder
- Tension
- Drowsiness
- Hostility
- Lethargy
- Nightmares
Dermatologic:
- Skin Rash
Gastrointestinal:
- Flatulence
- Constipation
- Dysgeusia
- Abdominal Pain
- Diarrhea
- Xerostomia
- Dyspepsia
- Increased Appetite
- Anorexia
- Decreased Appetite
- Gastroesophageal Reflux Disease
Respiratory:
- Upper Respiratory Tract Infection
- Dyspnea
- Rhinorrhea

Contraindication to Varenicline (Chantix) Include:

Varenicline and any other component can cause severe allergic reactions or skin reactions.

Warnings and precautions

CNS depression:
- CNS depression can lead to mental or physical impairments.
- It is important to warn patients about tasks that require mental alertness, such as driving or operating machinery.
Hypersensitivity reactions
- There have been rare cases of severe skin reactions, including angioedema and hypersensitivity reactions, such as Stevens-Johnson syndrome or erythema multifemale.
- If symptoms or signs develop, patients should stop using the medication and consult their doctor immediately.
Nausea:
- Nausea can be dose-dependent
- We have seen both persistent and transient nausea.
- For nausea that is not controlled, a reduction in dosage may be necessary.
Neuropsychiatric effects
- Patients with and without a preexisting psychiatric disorder have had serious neuropsychiatric events, including suicidal thoughts and suicide attempts.
- All patients should be monitored for any behavioral changes or psychiatric symptoms (eg depression, agitation, suicidal ideation, suicidal behavior).
- If patients experience mood or behavioral changes, they should immediately contact their doctor and discontinue any treatment.
Somnambulism:
- There have been cases of somnambulism, which can lead to harm to oneself, others, or property.
- Stop treatment if somnambulism occurs.
Cardiovascular events
- The risk of developing a heart attack can be increased by treatment.
- If you experience symptoms of cardiovascular disease, it is important to notify your doctor immediately.
Renal impairment
- Patients with impaired renal function should be careful
- With severe impairment, dosage adjustment may be required.
Seizures:
- Patients with and without a history have experienced seizures.
- Seizures are most common within the first month of treatment.
- Patients with a history or other factors that could lower the seizure threshold should weigh the risks against the benefits before they are started.
- If seizures occur during therapy, stop immediately.

Varenicline: Drug Interaction

Risk Factor C (Monitor therapy)
Alcohol (Ethyl)	Varenicline may enhance the adverse/toxic effect of Alcohol (Ethyl). Specifically, alcohol tolerance may be decreased and the risk for neuropsychiatric adverse effects may be increased.
Erdafitinib	May increase the serum concentration of OCT2 Substrates.
Histamine H2 Receptor Antagonists	May increase the serum concentration of Varenicline. Management: Monitor for increased varenicline adverse effects with concomitant use of cimetidine or other H2-antagonists, particularly in patients with severe renal impairment. International product labeling recommendations vary. Consult appropriate labeling.
Nicotine	Varenicline may enhance the adverse/toxic effect of Nicotine.
Quinolones	May increase the serum concentration of Varenicline. Management: Monitor for increased varenicline adverse effects with concurrent use of levofloxacin or other quinolone antibiotics, particularly in patients with severe renal impairment. International product labeling recommendations vary. Consult appropriate labeling.
Trimethoprim	May increase the serum concentration of Varenicline. Management: Monitor for increased varenicline adverse effects with concomitant use of trimethoprim, particularly in patients with severe renal impairment. International product labeling recommendations vary. Consult appropriate labeling.
Risk Factor D (Consider therapy modification)
Tafenoquine	May increase the serum concentration of OCT2 Substrates. Management: Avoid use of OCT2 substrates with tafenoquine, and if the combination cannot be avoided, monitor closely for evidence of toxicity of the OCT2 substrate and consider a reduced dose of the OCT2 substrate according to that substrate's labeling.

Monitor:

Monitor for behavioral changes and psychiatric symptoms (eg, agitation, depression, suicidal behavior, and suicidal ideation).

How to administer Varenicline (Chantix)?

Administer after eating and with a full glass of water.

Mechanism of action of Varenicline:

Partial neuronal a4 b4 nicotinic receptor agonist
It stops nicotine stimulation of the mesolimbic nopamine system that is associated with nicotine addiction.
It also binds to 5-HT3 receptors with moderate affinity.
Varenicline stimulates dopamine activity, but in a smaller degree than nicotine.
This results in decreased cravings and withdrawal symptoms.

Absorption: Well absorbed and unaffected by food

Protein binding is less than 20%

Metabolism: Minimal (<10% of clearance is by metabolism)

Bioavailability is about 90%

Half-life elimination is about 24 hours

The time to reach peak plasma concentration is about 3 - 4 hours

It is excreted mainly in the urine (92% as unchanged drug)

International Brands of Varenicline: