What are the pharmacology and oral administration recommendations for cyclosporine?

Pharmacology and Oral Administration of Cyclosporine

Cyclosporine is a potent, non-cytotoxic immunosuppressant that works by binding to cytoplasmic cyclophillin and inhibiting calcineurin phosphatase, thereby suppressing T-helper cell activation and lymphokine production. 1

Mechanism of Action

Cyclosporine selectively suppresses the T-helper (Th1/Th2) cell response through inhibition of lymphocyte activation. Specifically, it:

• Binds to cyclophillin (a family of cis-trans isomerases) in the cytoplasm
• Inhibits calcineurin phosphatase, preventing dephosphorylation of nuclear factor of activated T cells
• Blocks transcription of lymphokines including IL-2, interferon-gamma, GM-CSF, IL-3, IL-4, and TNF-alpha 1

Additional properties include inhibition of antigen-presenting cell function, mast cell mediator release (histamine and prostaglandins), keratinocyte proliferation, and keratinocyte cytokine secretion 1.

Pharmacokinetics

Absorption and Bioavailability

The microemulsion formulation (Neoral) has largely superseded the original olive oil formulation due to more consistent pharmacokinetics and reduced variability in absorption. 1 Key characteristics:

• Oral bioavailability: Approximately 40% with original formulation; microemulsion yields ~10% higher bioavailability 1
• Peak concentrations: Reached in 1-8 hours after oral dosing 2
• Food effects: Greater absorption occurs with preprandial (before meal) administration compared to postprandial 1

Distribution and Metabolism

• Volume of distribution: 0.9-4.8 L/kg (whole blood; HPLC) 2
• Blood to plasma ratio: Approximately 2:1 (highly bound to erythrocytes) 2
• Plasma protein binding: ~80% bound to lipoproteins 2
• Metabolism: Extensively metabolized primarily by CYP3A4 (and CYP3A isoenzymes) through mono- and dihydroxylation and N-demethylation 1, 3
• Excretion: Metabolites primarily excreted through bile and feces; only 3-6% excreted in urine 1
• Plasma half-life: Approximately 6.3 hours in healthy volunteers 1

Critical consideration: Cyclosporine has a narrow therapeutic index, requiring careful dose titration to balance efficacy against toxicity 1.

Oral Administration Guidelines

Dosing for Psoriasis (Primary Dermatologic Indication)

Initial dosing: Start at 2.5 mg/kg/day divided into two doses (morning and evening), though once-daily dosing is acceptable 3. For rapid control, 5 mg/kg/day may be used initially 1.

Dose titration:

• If inadequate response after 4 weeks at 2.5 mg/kg/day, increase by 0.5 mg/kg/day every 2 weeks to maximum of 4 mg/kg/day 3
• Reduce dose by 25-50% for adverse events (hypertension, creatinine elevation ≥25% above baseline, or other significant abnormalities) 3
• Once controlled, titrate down in steps of 0.5-1 mg/kg to lowest effective maintenance dose 1

Treatment duration:

• Short courses of 2-4 months are recommended 1
• Discontinue if no satisfactory response after 6 weeks at 4 mg/kg/day 3
• Continuous treatment beyond 1 year is not recommended; alternation with other treatments should be considered 3

Preparation and Administration Instructions

For oral solution (microemulsion):

1. Dilute with orange or apple juice at room temperature using the provided dosing syringe 3
2. Use a glass container (not plastic) 3
3. Stir well and drink immediately—do not allow diluted solution to stand 3
4. Rinse glass with more diluent to ensure complete dose consumption 3
5. Dry the dosing syringe with clean towel after use; do not rinse with water 3

Critical warnings:

• Avoid grapefruit and grapefruit juice—they inhibit CYP3A4 metabolism and increase cyclosporine blood levels 1, 3
• Avoid milk as diluent—combination is unpalatable 3
• Take consistently with regard to time of day and relation to meals 3
• Avoid switching diluents frequently 3

Monitoring Requirements

First 2 months:

• Serum creatinine and blood pressure every 2 weeks 1
• CBC, uric acid, potassium, lipids, magnesium every 2 weeks 3

After 2 months (if stable):

• Monthly monitoring of above parameters 1
• Every 2-3 months for long-term stable patients after 4 months 1

Creatinine management algorithm:

• If creatinine rises ≥25% above baseline: Repeat within 2 weeks; if sustained, reduce dose by 25-50% 3
• If creatinine rises ≥50% above baseline: Reduce dose by 25-50% immediately 3
• Discontinue if reversibility not achieved after two dose modifications 3

Blood pressure management:

• Reduce dose by 25-50% for sustained hypertension 3
• If hypertension persists despite dose reductions, discontinue cyclosporine 3
• Calcium channel blockers (especially isradipine) are preferred antihypertensives; avoid thiazide and potassium-sparing diuretics 4

Contraindications and Precautions

Absolute contraindications:

• Uncontrolled hypertension or abnormal renal function 1
• Active serious infections 1
• History of lymphoma or melanoma 1
• Inability to comply with monitoring 1

Drug interactions to avoid:

• NSAIDs (potentiate renal dysfunction, especially with dehydration) 3
• Nephrotoxic drugs (aminoglycosides, amphotericin B, trimethoprim-sulfamethoxazole) 3
• CYP3A4 inhibitors increase cyclosporine levels (azole antifungals, macrolide antibiotics, calcium channel blockers, HIV protease inhibitors) 3
• Live-attenuated vaccines are contraindicated during treatment 1

Special Populations

Pregnancy: Not teratogenic based on transplant experience, but avoid when possible; may be used for severe pustular psoriasis in pregnancy 1

Lactation: Passes into breast milk; mothers generally advised to avoid breastfeeding 1

Children: Can be used in children ≥2 years for atopic dermatitis; effective and relatively well-tolerated in short courses 1

Clinical Pearls

• Onset of benefit: Patients typically show improvement within 2 weeks; satisfactory control may take 12-16 weeks 3
• PASI 75 response: Achieved in 51% at 8 weeks and 79% at 16 weeks with dose titration 3
• Relapse timing: Occurs in approximately 6 weeks (50% of patients) to 16 weeks (75% of patients) after stopping 3
• Rebound is uncommon: Majority of patients do not experience rebound after cessation 3
• Intermittent courses are safer than continuous treatment for reducing cumulative renal toxicity risk 1