Relative bioavailability of a new oral form of cyclosporin A in patients with rheumatoid arthritis

Geropharmacology for the rheumatologist

Drug administration to older patients with rheumatic disease is a challenge because they are more likely to have adverse drug reactions compared with younger patients. Elderly patients are at risk for adverse drug effects because they often have multiple acute and chronic illnesses and are on several prescription and over-the-counter medications. This article will enhance the practitioner's understanding of how disease and age modulate the pharmacokinetics and pharmacodynamics of medications commonly prescribed for rheumatic disorders. Minimizing the number of drugs prescribed, starting medications at low doses and increasing slowly, and monitoring for toxicity are especially important in the elderly. With judicious use of medications, the quality of life of older patients with rheumatic disease can be enhanced.

Microemulsion formulation of cyclosporin (Sandimmun Neoral) vs Sandimmun: comparative safety, tolerability and efficacy in severe active rheumatoid arthritis. On behalf of the OLR 302 Study Group

OBJECTIVE

To compare the safety, tolerability and efficacy of the new oral microemulsion formulation of cyclosporin A (CyA; Sandimmun Neoral) and the original CyA formulation (Sandimmun), in patients with severe active rheumatoid arthritis (RA), over a 12-month period.

METHODS

In this double-blind, multicentre study, patients were randomized to treatment with Neoral or Sandimmun, starting with 2.5 mg/kg/day, with dose adjustments after 4 weeks. Primary efficacy criteria included patients' assessment of disease activity. Pharmacokinetic and safety assessments were performed at regular intervals.

RESULTS

Compared with Sandimmun, Neoral showed a consistent trend towards greater clinical efficacy from week 12 onwards, including a significant difference in patients' assessment of disease activity at the study end-points. A significantly lower increase in dose from baseline was observed with Neoral at week 24. Pharmacokinetic assessments at week 24 showed increased absorption and decreased variability with Neoral. No differences in safety were found between treatment groups.

CONCLUSION

These observations indicate that Neoral is as safe and at least as effective as Sandimmun and have important implications for patient management given the increasing role for CyA in the treatment of severe, active RA.

The use of Neoral in rheumatoid arthritis

Neoral (a microemulsion-based formulation) is an immunomodulator that possesses a more predictable and improved absorption than the conventional oral formulation (Sandimmun). The increased bioavailability of Neoral could result in improved efficacy. The pharmacokinetics of cyclosporin and efficacy of cyclosporin in rheumatoid arthritis are reviewed in this article. Current guidelines for the use of Neoral in the treatment of rheumatoid arthritis patients are outlined.

Drug treatment of rheumatic diseases in the 1990s. Achievements and future developments

There have been several advances in the therapy of arthritis. These are based on better understanding of the pathogenesis of rheumatic diseases, re-evaluation of previous therapeutic concepts such as combination therapy, and developments within biotechnology. There are 4 main areas of development, mainly involving the treatment of inflammatory synovitis. The first is with anti-inflammatory drugs, where there has been a focus on reducing gastrointestinal toxicity through the use of combination preparations such as diclofenac-misoprostol, and the introduction of drugs with more selectivity for cyclo-oxygenase-2 inhibition such as meloxicam. An additional approach has been the development of anti-inflammatory drugs such as tenidap which also control cytokine metabolism. The second area is slow-acting antirheumatic drugs with the introduction of cyclosporin as a single agent or in combination with methotrexate, the development of immunomodulating drugs such as leflunomide, and the demonstration that some antibiotics such as minocycline have slow-acting effects. The third area is the use of corticosteroids including the development of deflazacort as a bone sparing agent, the greater use of intramuscular depot steroids and the validation of low-dose oral corticosteroids in early rheumatoid arthritis. Finally, there have been advances in the biotechnology area with the demonstration that cytokine immunotherapy such as antibodies to tumour necrosis factor can rapidly improve the symptoms of rheumatoid arthritis, and that T cell immunotherapy with antibodies to the CD4 receptor may be effective in reducing synovitis. Many of these agents have not yet been introduced into clinical practice but they show the diversity of drug development and suggest the likelihood of major therapeutic benefits in the next few years.

Cyclosporin. A review of the pharmacokinetic properties, clinical efficacy and tolerability of a microemulsion-based formulation (Neoral)

The microemulsion-based formulation of cyclosporin (Neoral; referred to as the microemulsion formulation in this review) is a microemulsion preconcentrate which has been developed to overcome problems associated with the poor and unpredictable absorption of the standard oral formulation of this drug. These include marked intra- and interpatient variability in the extent of absorption, a poor correlation between trough blood concentrations of cyclosporin and total systemic exposure, and the need for regular monitoring of blood cyclosporin concentrations. In healthy volunteers and renal or liver transplant recipients, administration of the microemulsion formulation resulted in cyclosporin absorption which was significantly faster, more extensive and more predictable than that seen with the standard oral formulation. Furthermore, measurement of whole-blood trough cyclosporin concentrations provided a better estimate of systemic drug exposure in renal transplant recipients who received the microemulsion formulation than in those who received the standard formulation. Systemic exposure of cyclosporin delivered by the new formulation appears to be relatively unaffected by food intake. Initial data suggest that drug absorption from the microemulsion formulation is enhanced in comparison with that achieved from the standard formulation in liver transplant recipients undergoing biliary diversion or with cholestasis, although absorption from the new formulation does not appear to be completely independent of bile. Preliminary results from other groups that experience cyclosporin malabsorption from the standard formulation (patients with cystic fibrosis or diabetes, and children) are also encouraging. Clinical trials specifically designed to investigate the relative immunosuppressive efficacy of the microemulsion formulation have not been reported; further data are required to fully establish the relationship between the more rapid and extensive absorption of cyclosporin from the microemulsion formulation and the probability of graft rejection or adverse events (including nephrotoxicity and hypertension). However, no statistically significant differences have been noted between the 2 formulations in the incidence of these events in studies to date. The incidence of rejection in new renal or liver transplant recipients treated for a minimum of 3 months was approximately 31 to 50% in those receiving the microemulsion formulation and approximately 24 to 56% in those receiving the standard formulation. Thus, although confirmation of existing efficacy and tolerability data is required, the characteristic pharmacokinetic properties of the microemulsion formulation make it an attractive option for the oral delivery of cyclosporin in transplant recipients, offering more predictable and more extensive drug absorption than the standard formulation. The microemulsion formulation may be of particular benefit in patients who show poor absorption of cyclosporin from the standard oral formulation, such as liver transplant recipients with biliary diversion or cholestasis.

Clinical use of cyclosporin in rheumatoid arthritis

Rheumatoid arthritis is a chronic immune-mediated disease characterised by an inflammatory synovitis and extra-articular manifestations. There is an expanding body of evidence to indicate that the activation of T lymphocytes is central in the initiation and perpetuation of this disease. Cyclosporin is an immunomodulator and a highly specific inhibitor of T-lymphocyte function, and has demonstrated disease-modifying properties in clinical studies in patients with rheumatoid arthritis. A concern with the use of cyclosporin has been the development of dose-dependent adverse effects, in particular renal dysfunction. Cyclosporin is lipophilic by nature and the conventional oral formulation (Sandimmun) was subject to incomplete and highly variable absorption, resulting in substantial inter- and intrasubject variations in peak concentrations and systemic bioavailability. A microemulsion-based formulation of cyclosporin (Neoral) has recently been developed, and possesses more predictable and improved absorption with a consequent increased peak concentration and systemic bioavailability. The improved predictability of absorption, and hence blood concentrations, facilitates the ability to 'tailor' therapy to an individual patient, which, in theory, could translate into an improved efficacy and safety profile.

Safety aspects of cyclosporin in rheumatoid arthritis

While cyclosporin has an established role in the management of patients with rheumatoid arthritis, its use can be accompanied by various adverse events. In daily practice, the potential for cyclosporin to induce nephropathy is of most concern and has, to some extent, limited the use of this drug. However, these effects on renal function are dose dependent. Two international meetings have resulted in the publication of guidelines aimed at limiting the risk of adverse events when cyclosporin is used in patients with rheumatoid arthritis. The 1994 International Consensus guidelines with respect to renal safety recommend the principal dosage regimen of 'go low, go slow', which requires starting patients on a daily dose of between 2.5 and 3.5 mg/kg with the maximum daily dose not exceeding 5 mg/kg. The cyclosporin dosage chosen should be titrated against the highest acceptable increase in serum creatinine, i.e. a 30% increase over the baseline value. Renal biopsy data support these guidelines, and when the latter are followed by physicians, it is very unlikely that histological damage will occur. The new oral microemulsion-based formulation of cyclosporin (Neoral) has a more predictable absorption and a 20% greater bioavailability than the conventional formulation (Sandimmun). Therefore, the microemulsion formulation may enable more patients to receive effective treatment at lower doses. This could have interesting safety and pharmacoeconomic implications.