Baricitinib

• Rheumatoid Arthritis
• COVID-19
• Alopecia Areata
• Autoimmune Conditions

Baricitinib is a Janus kinase (JAK) inhibitor approved for the treatment of rheumatoid arthritis, COVID-19, and alopecia areata. This oral targeted synthetic disease-modifying antirheumatic drug (tsDMARD) represents a significant advancement in treating inflammatory and immune-mediated conditions.

Mechanism of Action

Baricitinib inhibits Janus kinases JAK1 and JAK2, which are intracellular enzymes that transmit signals from cytokine and growth factor receptors. When cytokines bind to their receptors, JAKs phosphorylate STAT (signal transducer and activator of transcription) proteins, which then translocate to the nucleus and modulate gene transcription. By inhibiting JAK1/JAK2, baricitinib blocks signaling from numerous pro-inflammatory cytokines including IL-6, IL-12, IL-23, IFN-gamma, and GM-CSF. This broad inhibition of inflammatory pathways reduces joint inflammation and damage in rheumatoid arthritis and modulates immune responses in other conditions.

Available Formulations

Baricitinib is available as oral tablets in 1 mg and 2 mg strengths. The tablets can be taken with or without food. The medication should be stored at room temperature.

Medical Uses

Baricitinib is FDA-approved for moderately to severely active rheumatoid arthritis in adults who have had an inadequate response to one or more TNF antagonists, hospitalized adults with COVID-19 requiring supplemental oxygen, invasive mechanical ventilation, or ECMO, and for severe alopecia areata in adults. In rheumatoid arthritis, it may be used as monotherapy or in combination with methotrexate or other DMARDs. Clinical trials demonstrated significant improvements in symptoms, physical function, and radiographic progression.

Dosing Guidelines

For rheumatoid arthritis, the recommended dose is 2 mg once daily. For alopecia areata, the recommended dose is 2 mg once daily, which may be increased to 4 mg once daily for inadequate response. For COVID-19, the dose is 4 mg once daily for 14 days or until hospital discharge. Dose reductions are required for renal impairment: 1 mg daily for moderate impairment (CrCl 30-60 mL/min); not recommended for severe impairment. Lymphocyte, neutrophil, and hemoglobin levels should be assessed before and during treatment.

Important Safety Information

Baricitinib carries a boxed warning for serious infections, mortality, malignancies, major adverse cardiovascular events (MACE), and thrombosis. Patients should be tested for latent tuberculosis before starting therapy. Live vaccines should not be given during treatment. The medication should not be used with other JAK inhibitors, biologic DMARDs, or potent immunosuppressants. Laboratory monitoring is required including CBC, lipids, and liver enzymes.

Drug Interactions

Strong OAT3 inhibitors (probenecid) increase baricitinib exposure; dose reduction to 1 mg daily is recommended. Baricitinib is not a significant CYP enzyme substrate, inducer, or inhibitor. It may be used with non-biologic DMARDs including methotrexate and sulfasalazine. Concurrent use with other JAK inhibitors, biologic DMARDs, or potent immunosuppressants (cyclosporine, azathioprine) is not recommended.

Special Populations

Baricitinib may cause fetal harm based on animal studies; females of reproductive potential should use effective contraception during treatment and for one week after the last dose. Breastfeeding is not recommended during treatment and for 4 days after the last dose. Safety and efficacy have not been established in pediatric patients for RA or alopecia. Elderly patients may be at increased risk for serious adverse events. Dose adjustment is required for moderate renal impairment; the medication is not recommended for severe renal impairment or end-stage renal disease.