What is Cyclosporine?
Cyclosporine (also spelled ciclosporin) is a potent, non-cytotoxic immunosuppressive drug derived from the soil fungus Tolypocladium inflatum, first isolated in 1970, that works by selectively inhibiting T-cell activation through calcineurin inhibition. 1
Chemical Structure and Origin
Cyclosporine is a neutral, hydrophobic cyclic polypeptide containing 11 amino acids with a molecular weight of 1203 Da. 1 It was discovered in the early 1970s and revolutionized transplant medicine by enabling organ transplantation on a scale previously impossible. 2
Mechanism of Action
The drug works through a highly specific immunosuppressive pathway:
- Primary target: T-helper cells (Th1/Th2), though T-suppressor cells may also be affected 1
- Molecular mechanism: Cyclosporine binds to cytoplasmic cyclophillin, which then inhibits calcineurin phosphatase 1
- Result: This prevents dephosphorylation of nuclear factor of activated T cells (NFAT), blocking its entry into the nucleus and suppressing transcription of key cytokines including:
Additional mechanisms include inhibition of antigen-presenting cells, mast cell mediator release (histamine and prostaglandins), keratinocyte proliferation, and keratinocyte cytokine secretion. 1
Importantly, cyclosporine does NOT cause bone marrow suppression, distinguishing it from cytotoxic immunosuppressants. 3
Clinical Applications
Primary Indications:
- Organ transplantation: Prevention of kidney, liver, heart, pancreas, bone marrow, and lung transplant rejection 3
- Dermatology: FDA-approved for severe psoriasis (1997); also used for atopic dermatitis 1, 4
- Ophthalmology: Topical formulations for dry eye disease and inflammatory ocular surface conditions 5
- Nephrology: Nephrotic syndrome, particularly in steroid-dependent or frequently relapsing cases 2
Off-Label Uses:
Cyclosporine has demonstrated efficacy in numerous autoimmune and inflammatory conditions including rheumatoid arthritis, Crohn's disease, Behçet's syndrome, uveitis, aplastic anemia, pyoderma gangrenosum, and various blistering disorders. 6
Formulations and Pharmacokinetics
Two oral formulations exist:
- Original formulation (Sandimmune®): Simple solution in olive oil with variable absorption 1
- Microemulsion formulation: Now standard, with improved and more consistent bioavailability, requiring approximately 10% lower dosing for equivalent efficacy 1
Key pharmacokinetic properties:
- Incomplete oral absorption (approximately 40% for original formulation) 1
- Primarily biliary elimination; only 6% excreted in urine 3
- Biphasic blood disposition with terminal half-life of approximately 8.4 hours (range 5-18 hours) 3
- Extensive metabolism by CYP3A4 enzymes 3
- Substrate of P-glycoprotein efflux transporter 3
Critical Safety Considerations
Cyclosporine has a narrow therapeutic index, requiring careful balance between efficacy and toxicity. 1
Major Hazards:
1. Nephrotoxicity (most important concern):
- Dose-related and potentially irreversible with chronic use 2
- Causes increased vascular resistance, reduced renal blood flow, and elevated serum creatinine 2
- Monitoring requirement: Reduce dose if serum creatinine increases by 30% above baseline, even if within normal range 2
2. Hypertension: Common and requires monitoring 1
3. Increased infection risk: Due to immunosuppression 1
4. Malignancy risk:
- Increased risk of non-melanoma skin cancer, particularly in patients previously exposed to high-dose UV radiation 1
- Contraindication: Should NOT be used concurrently with phototherapy 1
- No established increased risk of internal malignancy in dermatology patients (except transplant recipients) 1
5. Other adverse effects:
- Hypertrichosis and gingival hyperplasia (common but usually mild) 6
- Hyperlipidemia (triglycerides and cholesterol elevation) 1
- Neurological effects: paresthesia, tremor, headaches 1
Clinical Positioning
Cyclosporine is generally reserved for severe disease and considered a second-line agent, especially when treatment duration exceeds 2-3 months. 1 This reflects the need to balance its high efficacy against significant toxicity risks, particularly nephrotoxicity and hypertension.
Drug Interactions
Critical interactions due to CYP3A4 metabolism:
- Avoid grapefruit juice: Increases cyclosporine blood levels 3
- Drugs increasing levels: Calcium channel blockers (diltiazem, verapamil), azole antifungals, macrolide antibiotics, protease inhibitors 3
- Drugs decreasing levels: Rifampin, anticonvulsants (phenytoin, carbamazepine), St. John's Wort 3
- Nephrotoxic drug combinations: NSAIDs, aminoglycosides, amphotericin B require extreme caution 3
Monitoring Requirements
Mandatory monitoring includes: