Israel Medical Association Journal

Background: Traditionally, medication dosage was based on clinical and demographic parameters, but drug metabolism was recently recognized as an important factor for proper dosing and prediction of side effects. Metabolic considerations are crucial when administering drugs with a narrow therapeutic index, such as those of the thioguanides family (azathioprine and 6-MP). These can cause life-threatening myelosuppression due to low activity of a critical metabolic enzyme, thiopurine S-methyl transferase. A number of single nucleotide substitutions encoding variant enzymes account for most enzyme deficiencies.

Objectives: To determine the frequency of individuals from different Israeli ethnic groups who may be at risk for drug toxicity from drugs of the thioguanide family due to enzymatic variants.

Methods: DNA analysis was performed using polymerase chain reaction methods. We tested TPMT[1] allelic variants TPMT*3A (G460A, A719G), TPMT*3B (G460A) and TPMT*3C (A719G) in five subpopulations in Israel: mixed-origin Israeli Jews, Arabs, Druze, Jews of Kurdish extraction, and Ethiopian Jews.

Results: The Druze (P = 0.0002) and Ethiopian Jewish (P = 0.015) subpopulations had a significantly unique distribution of allelic variants compared to the rest of the Israeli population. The Druze subpopulation showed a high number of TPMT variants with decreased activity, and a homozygote for TPMT*3A/ *3A was detected.  Ethiopian Jews were found to carry mainly the TPMT*3C variant, also observed in other studies of African populations.

Conclusions: It is advisable that Druze patients be tested for the TPMT enzyme before starting treatment with 6-MP or azathioprine. Such testing may also be considered for other Israeli ethnic subgroups.

Background: Low density lipoprotein apheresis is used as a complementary method for treating hypercholesterolemic patients who cannot reach target LDL[1]-cholesterol levels on conventional dietary and drug treatment. The DALI system (direct absorption of lipoproteins) is the only extracorporeal LDL-removing system compatible with whole blood.

Objective: To describe our one year experience using the DALI[2] system.

Methods: LDL apheresis was used in 13 patients due to inability to reach target LDL-C levels on conventional treatment. They included seven patients with familial hypercholesterolemia, three who had adverse reactions to statins, and three patients with ischemic heart disease who did not reach LDL-C target level on medical treatment.

Results: The average triglyceride, total cholesterol, high density lipoprotein-C and LDL-C levels before and after treatment in all patients were: 170 ± 113 vs. 124 ± 91, 269 ± 74 vs. 132 ± 48, 42 ± 8 vs. 37 ± 7.9, and 196 ± 77 vs. 80 ± 52 mg/dl, respectively. Comparing the results of a subgroup of seven patients who had previously been treated with plasma exchange, it is noteworthy that while the reduction in triglyceride, total cholesterol and LDL-C are comparable, the effect on HDL[3]-C concentration was less apparent: from an average of 39.7 ± 8.7 and 23 ± 5.7 mg/dl before and after plasma exchange to an average of 43.9 ± 8.1 and 38.4 ± 7 mg/dl before and after LDL apheresis, respectively. Five patients developed treatment-related adverse events: three experienced allergic reactions manifested as shortness of breath, urticaria and facial flushing; one patient developed rhabdomyolysis, an adverse reaction that was not reported previously as a result of LDL apheresis; and one patient had myopathy with back pain. All untoward effects occurred during the first few treatment sessions.

Conclusions: LDL apheresis using the DALI system is highly efficacious for the treatment of hypercholesterolemia. It is associated with a significant number of side effects occurring during the first treatment sessions. In patients not experiencing adverse effects in the early treatment period, it is well tolerated, and can provide remarkable clinical benefit even after short-term therapy.

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