Tofacitinib is an oral medication used in the treatment of autoimmune and inflammatory diseases. It belongs to a class of drugs known as Janus kinase (JAK) inhibitors. Tofacitinib works by blocking specific enzymes involved in immune system signaling. This action helps reduce inflammation and abnormal immune responses. It is commonly prescribed for conditions such as rheumatoid arthritis, psoriatic arthritis, and ulcerative colitis. The drug is usually taken by mouth in tablet form. Tofacitinib helps improve symptoms like pain, swelling, and joint stiffness. Patients using this medication require regular medical monitoring. Common side effects may include infections and changes in blood counts. Overall, tofacitinib represents an important advancement in targeted immunotherapy.
BRAND NAMES
Xeljanz®
Xeljanz XR®
Jakvinus®
TofaJAK®
Tofanib®
MECHANISM OF ACTION
Tofacitinib works by inhibiting Janus kinases (JAKs), mainly JAK1 and JAK3. These enzymes are involved in signaling pathways that activate immune responses. By blocking JAK activity, the drug reduces cytokine production. This leads to decreased inflammation and immune overactivity. As a result, symptoms of autoimmune diseases are controlled.
PHARMACOKINETICS
Absorption
Tofacitinib is well absorbed after oral administration. Peak plasma concentrations are reached within 0.5 to 1 hour. Food does not significantly affect its absorption. The oral bioavailability is approximately 74%. This allows effective treatment through oral dosing.
Distribution
The drug is moderately bound to plasma proteins. It is widely distributed throughout body tissues. Tofacitinib can reach inflamed joints and intestinal tissues. The volume of distribution supports systemic action. This contributes to its effectiveness in autoimmune diseases.
Metabolism
Tofacitinib is primarily metabolized in the liver. The enzyme CYP3A4 plays a major role, with minor involvement of CYP2C19. Drug interactions may occur with CYP inhibitors or inducers. Metabolism converts the drug into inactive metabolites. Liver function affects drug clearance.
Excretion
Tofacitinib is eliminated through both urine and feces. About 30% is excreted unchanged in urine. The remaining portion is excreted as metabolites. The elimination half-life is approximately 3 hours. Renal function influences excretion rate.
PHARMACODYNAMICS
Tofacitinib reduces immune cell activation and inflammatory mediator release. It decreases levels of cytokines involved in autoimmune diseases. The drug improves symptoms such as pain, swelling, and stiffness. Clinical improvement is seen within weeks. Its action is dose-dependent and reversible.
ADMINISTRATION
Tofacitinib is administered orally. It is available as immediate-release and extended-release tablets. The drug should be taken exactly as prescribed. Tablets should not be crushed or chewed. Regular monitoring is required during therapy.
DOSAGE AND STRENGTH
Tofacitinib is available in strengths such as 5 mg and 10 mg tablets, and 11 mg extended-release tablets. Dosage depends on the disease being treated. It is commonly given once or twice daily. Dose adjustments are needed in liver or kidney impairment. Long-term use requires medical supervision.
DRUG INTERACTIONS
Tofacitinib interacts with drugs affecting CYP3A4 enzymes. Strong inhibitors may increase drug levels. Inducers can reduce its effectiveness. Combining with other immunosuppressants increases infection risk. Careful monitoring is necessary when used with other medications.
FOOD INTERACTIONS
Food does not significantly affect the absorption of tofacitinib. It can be taken with or without meals. However, grapefruit may increase drug levels by inhibiting metabolism. Patients are advised to avoid grapefruit products. Consistent timing improves effectiveness.
CONTRAINDICATIONS
Tofacitinib is contraindicated in patients with severe infections. It should not be used in individuals with known hypersensitivity to the drug. Active tuberculosis is a contraindication. Caution is required in severe liver disease. Use during pregnancy requires medical advice.
SIDE EFFECTS
Headache
Diarrhea
Nausea or vomiting
Upper respiratory tract infections (e.g., common cold, sinusitis)
Sore throat, cough
Nasal congestion (nasopharyngitis)
High blood pressure (hypertension)
Raised cholesterol levels
Low red or white blood cell counts (anemia, lymphopenia, neutropenia)
OVER DOSE
Overdose of tofacitinib may increase the risk of adverse effects. Symptoms can include severe infections or laboratory abnormalities. There is no specific antidote. Treatment is supportive and symptomatic. Immediate medical attention is required in overdose cases.
TOXICITY
Long-term use may increase the risk of serious infections and blood clots. Liver enzyme elevation and hematologic toxicity may occur. Toxicity is dose-related. Monitoring of blood tests is essential. Proper dosing minimizes toxic effects.
