Browsing by Author "Stephan, Antoine"

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A Novel Approach in Clinical Immunosuppression Monitoring: Drug Lymphocyte Level
(Başkent Üniversitesi, 2007-12) Barbari, Antoine; Masri, Marwan A.; Stephan, Antoine; Rizk, Sylvana; Younan, Farida
Like others, we have shown a weak correlation between drug blood levels and clinical outcome and immune response. We recently established that in contrast to blood levels, drug lymphocyte levels are strongly associated with therapeutic efficacy. The discordance between the 2 methodologies regarding clinical outcome and immune response is related mainly to the weak association between drug blood level and target-cell content. This weak association explains the intra- and interindividual variabilities of the therapeutic response. These variations are related mainly to genetic and environmental factors including age, sex, body mass index, organ function, food and subsequent drug absorption, drug interactions, and the availability of extra–target-cell binding sites. These factors seem to influence the modes of action of immunosuppressive agents including drug absorption, metabolism, elimination, transport, extra–target-cell sites, as well as target-cell receptor expression and its binding affinity and specific enzyme baseline activity. Therefore, the cellular fraction of a drug at a fixed dosage is the result of the integration of out-fluxing and in-fluxing forces that are affected by genetic and environmental factors. Any redistribution of the drug between the different binding sites will ultimately affect its bioactivity with no change to its extracellular bioavailability (which is currently determined by pharmacokinetic measurements). Compared with whole-blood or plasma-level measurements, monitoring immunosuppression therapy at the site of action appears to be not only more clinically and immunologically relevant (since it measures the free fraction of the drug at its effector site), but this method also bypasses the potentially complex extracellular factors that affect bioactivity. Since the intracellular content of a drug strongly correlates with its biological effect, monitoring immunosuppression therapy at the site of action is comparable to pharmacodynamic monitoring. It is cost effective and easy to perform in clinical practice and could be used for all immunosuppressive drugs. Since it allows maximal reduction of adverse effects through dosage reduction while maintaining an optimal level of immunosuppression, it should offer a new alternative for immunosuppressive therapy monitoring and tailoring to the individual patient.
Middle East Society for Organ Transplantation (MESOT) Transplant Registry
(Başkent Üniversitesi, 2004-12) Haberal, Mehmet A.; Shaheen, Faissal A. M.; Stephan, Antoine; Ghods, Ahad J.; Al-Rohani, Muhamed; Mousawi, Mustafa Al; Mohsin, Nabil; Ben, Taieb; Bakr, Adel; Rizvi, Adibul Hasan
During the seventies, sporadic renal transplants were performed in few MESOT-region countries, mainly Turkey, Iran, Egypt, and Lebanon. Since the introduction of cyclosporine in the early eighties, transplantation has become the preferred therapeutic modality for end-stage renal failure. In 1986, the Islamic theologians (Al Aloma) issued what became known as the Amman declaration, in which they accepted brain death and retrieval and transplantation of organs from living and cadaveric donors. Based on this and similar declarations, all Middle Eastern countries except Egypt passed laws that allow cadaveric transplantation and regulate live donations. Iran, Turkey, Saudi Arabia, Kuwait, Tunisia, Jordan, and Lebanon all have current active cadaveric programs and perform liver, heart, pancreas, and lung transplants. More than 5088 renal transplants/year are performed in the region with Iran leading with 1600. The cumulative number of renal transplant patients is now nearly 60,000. With a 2003 population of 600,682,175, the rate/million for renal transplantation in the MESOT region is a mere 9/million. Rates of renal transplantation range from 31/million in some countries to 0 in others. The major obstacle in establishing an accurate number of transplants is “tourist transplantation,” in which the same transplanted patients are registered in different countries. Although cadaveric programs have been active for more than 10 years, live-related and nonrelated transplants account for nearly 85% of the total transplants. The data presented were collected from MESOT representatives in the region and from publications. For proper compilation of the registry, a format is being proposed that will be presented at the Congress for review and adaptation. Even with the limited resources in the region, immunosuppressive drugs for induction and maintenance therapy are available and are used. Costs for transplantation and immunosuppressive therapy are either totally or heavily supported by governmental agencies.