Pharmacological properties : תכונות פרמקולוגיות

Pharmacodynamic Properties

5.1   Pharmacodynamic properties
Pharmacotherapeutic group: Immunosuppressive agents, calcineurin inhibitors, ATC code: L04AD01 
Ciclosporin (also known as ciclosporin A) is a cyclic polypeptide consisting of 11 amino acids. It is a potent immunosuppressive agent, which in animals prolongs survival of allogeneic transplants of skin, heart, kidney, pancreas, bone marrow, small intestine or lung. Studies suggest that ciclosporin inhibits the development of cell-mediated reactions, including allograft immunity, delayed cutaneous hypersensitivity, experimental allergic encephalomyelitis, Freund's adjuvant arthritis, graft-versus-host disease (GVHD), and also T-cell dependent antibody production. At the cellular level it inhibits production and release of lymphokines including interleukin 2 (T-cell growth factor, TCGF).
Ciclosporin appears to block the resting lymphocytes in the G0 or G1 phase of the cell cycle, and inhibits the antigen-triggered release of lymphokines by activated T-cells.

All available evidence suggests that ciclosporin acts specifically and reversibly on lymphocytes.
Unlike cytostatic agents, it does not depress haemopoiesis and has no effect on the function of phagocytic cells.

Successful solid organ and bone marrow transplantations have been performed in man using ciclosporin to prevent and treat rejection and GVHD. Ciclosporin has been used successfully both in hepatitis C virus (HCV) positive and HCV negative liver transplants recipients. Beneficial effects of ciclosporin therapy have also been shown in a variety of conditions that are known, or may be considered to be of autoimmune origin.

Paediatric population: Ciclosporin has been shown to be efficacious in steroid-dependent nephrotic syndrome.

Pharmacokinetic Properties

5.2   Pharmacokinetic properties

Absorption
Following oral administration of Sandimmun Neoral peak blood concentrations of ciclosporin are reached within 1-2 hours. The absolute oral bioavailability of ciclosporin following administration of Sandimmun Neoral is 20 to 50%. About 13 and 33% decrease in AUC and Cmax was observed when Sandimmun Neoral was administered with a high-fat meal. The relationship between administered dose and exposure (AUC) of ciclosporin is linear within the therapeutic dose range. The intersubject and intrasubject variability for AUC and Cmax is approximately 10-20%. Sandimmun Neoral Oral Solution and Capsules are bioequivalent.

Distribution
Ciclosporin is distributed largely outside the blood volume, with an average apparent distribution volume of 3.5 l/kg. In the blood, 33 to 47% is present in plasma, 4 to 9% in lymphocytes, 5 to 12% in granulocytes, and 41 to 58% in erythrocytes. In plasma, approximately 90% is bound to proteins, mostly lipoproteins.

Biotransformation
Ciclosporin is extensively metabolised to approximately 15 metabolites. Metabolism mainly takes place in the liver via cytochrome P450 3A4 (CYP3A4), and the main pathways of metabolism consist of mono- and dihydroxylation and N-demethylation at various positions of the molecule. All metabolites identified so far contain the intact peptide structure of the parent compound; some possess weak immunosuppressive activity (up to one-tenth that of the unchanged drug).

Elimination
The excretion is primarily biliary, with only 6% of the oral dose excreted in the urine; only 0.1% is excreted in the urine as unchanged parent compound.

There is a high variability in the data reported on the terminal half-life of ciclosporin depending on the assay applied and on the target population. The terminal half-life ranged from 6.3 hours in healthy volunteers to 20.4 hours in patients with severe liver disease (see sections 4.2 and 4.4). The elimination half-life in kidney-transplanted patients was approximately 11 hours, with a range between 4 and 25 hours.

Special populations
Patients with renal impairment
In a study performed in patients with terminal renal failure, the systemic clearance was approximately two thirds of the mean systemic clearance in patients with normally functioning kidneys. Less than 1% of the administered dose is removed by dialysis.

Patients with hepatic impairment
An approximate 2- to 3-fold increase in ciclosporin exposure may be observed in patients with hepatic impairment. In a study performed in severe liver disease patients with biopsy-proven cirrhosis, the terminal half-life was 20.4 hours (range between 10.8 to 48.0 hours) compared to 7.4 to 11.0 hours in healthy subjects.

Paediatric population
Pharmacokinetic data from paediatric patients given Sandimmun Neoral or Sandimmun are very limited. In 15 renal transplant patients aged 3 -16 years, ciclosporin whole blood clearance after intravenous administration of Sandimmun was 10.6±3.7 ml/min/kg (assay: Cyclo-trac specific RIA). In a study of 7 renal transplant patients aged 2-16 years, the ciclosporin clearance ranged from 9.8 to15.5 ml/min/kg. In 9 liver transplant patients aged 0.65-6 years, clearance was 9.3±5.4 ml/min/kg (assay: HPLC). In comparison to adult transplant populations, the differences in bioavailability between Sandimmun Neoral and Sandimmun in paediatrics are comparable to those observed in adults.