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- INABA, T, et al.
(författare)
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Pharmacogenetics in clinical pharmacology and toxicology
- 1995
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Ingår i: Canadian journal of physiology and pharmacology. - : Canadian Science Publishing. - 0008-4212 .- 1205-7541. ; 73:3, s. 331-338
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Tidskriftsartikel (refereegranskat)abstract
- An international symposium entitled Pharmacogenetics in clinical pharmacology and toxicology: a tribute to Werner Kalow was held in Toronto, Ontario, July 20, 1994. This subject was particularly important to discuss in the presence of Werner Kalow, 77 years young, who is considered as one of the grandfathers of this unique combination of medical research fields. It has become increasingly appreciated that dozens of human drug metabolism polymorphisms exist. The interindividual variabilities in drug metabolism discussed at this symposium do not represent small differences such as 50% or 3-fold but, rather, represent 10- to greater than 1000-fold differences. When attributed to a single gene, dramatic differences can be seen among family members, just as blue and brown eyes can occur in siblings. These differences can result in acute drug toxicity. In addition, there are chronic effects: over one's lifetime, striking differences in the metabolism of drugs, occupationally hazardous chemicals, and other environmental pollutants can lead to interindividual differences in the buildup of DNA damage (e.g., mutations, chromosomal breaks, rearrangements) leading to toxicity and tumor initiation, as well as leading to a buildup in nongenotoxic signals (signal transduction pathways without DNA damage) important for toxicity, tumor promotion, and tumor progression. The human UDP glucuronosyltransferase (UGT superfamily is known to comprise more than 10 genes in humans, and probably in other mammalian species. Breakthroughs in UGT gene mutations responsible for the Crigler-Najjar syndrome and Gilbert's disease have recently been reported. The human cytochrome P450 termed CYP3A4 is a major P450 enzyme in the liver and gastrointestinal tract, and the full impact of the CYP3A4 polymorphism has yet to be fully appreciated. CYP3A4 metabolism of cyclosporin A, commonly prescribed to organ transplant recipients, the induction of CYP3A4 by rifampicin, and inhibition of CYP3A4 metabolism by erythromycin or ketoconazole are now quite well understood. The field of ethnopharmacology, or pharmacoanthropology, has recently emerged, pioneered at least in part by Kalow. Differences in debrisoquine–sparteine metabolism, S-mephenytoin hydroxylation, diazepam clearance, and omeprazole clearance in various Caucasian and Oriental subpopulations in a number of countries have been extensively reported. After a number of inconclusive studies, it has now been shown unequivocally that the human S-mephenytoin 4′-hydroxylase polymorphism represents at least two distinct mutations (one involving a splice site) in the CYP2C19 gene. Finally, the implications and clinical significance of a number of human polymorphisms (CYP2D6, CYP2C19, N-acetylation (NAT2), S-methylation by thiopurine methyltransferase (TPMT), and ester hydrolysis by plasma cholinesterase) were carefully reviewed at this symposium.Key words: pharmacology, toxicology, drug metabolism, pharmacogenetic polymorphism.
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| 3. |
- Travis, L. B., et al.
(författare)
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Bladder and kidney cancer following cyclophosphamide therapy for non-Hodgkin´s lymphoma
- 1995
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Ingår i: Journal of the National Cancer Institute. - : Oxford University Press (OUP). - 0027-8874 .- 1460-2105. ; 87:7, s. 524-530
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Recension (övrigt vetenskapligt/konstnärligt)abstract
- BACKGROUND: Cyclophosphamide is an established bladder carcinogen, but few studies have examined the relationship between dose and effect. The largest analysis to date included only seven cases of bladder cancer. No investigation has estimated the risk of kidney cancer. PURPOSE: The purpose of this study was to quantify the risk of bladder and kidney cancer following cyclophosphamide therapy. METHODS: Within a cohort of 6171 two-year survivors of non-Hodgkin's lymphoma (NHL), 48 patients with secondary cancer of the urinary tract were identified and matched to 136 control subjects with NHL who did not develop a second malignancy. Detailed information on chemotherapeutic drugs and cumulative dose received was collected for all subjects. Radiation dose to the target organ was estimated from individual radiotherapy records. Evaluations of the risk of second cancer as a result of treatment with cyclophosphamide alone, radiation alone, or both therapies were made relative to those patients who were exposed to neither treatment modality. RESULTS: A significant 4.5-fold risk of bladder cancer (95% confidence interval [CI] = 1.5-13.6) followed therapy with cyclophosphamide, and risk was dependent upon cumulative dose. Among patients who received a total amount of cyclophosphamide of less than 20 g, a nonsignificant 2.4-fold risk of bladder cancer was apparent. Significantly elevated sixfold (95% CI = 1.3-29) and 14.5-fold (95% CI = 2.3-94) risks of bladder malignancy followed cumulative doses of 20-49 g and 50 g or more, respectively (P value for trend = .004). Radiotherapy given without cyclophosphamide was associated with a nonsignificant increased risk of bladder malignancy. Excess bladder cancer risk following treatment with both radiotherapy and cyclophosphamide was as expected if individual risks were summed. Neither radiotherapy nor cyclophosphamide was associated with excesses of kidney cancer. CONCLUSIONS: Cyclophosphamide-related bladder cancer is dose dependent. For patients given cumulative doses between 20 and 49 g, the absolute risk of bladder cancer is on the order of three excess cancers per 100 NHL patients after 15 years of follow-up. At cumulative doses of 50 g or more, the excess risk increases to approximately seven excess bladder cancers per 100 NHL patients. IMPLICATIONS: The strong dose-response relationship and high absolute risk of bladder cancer underscore the importance of limiting the cumulative dose of cyclophosphamide to what is required to achieve therapeutic end points. The risk of secondary bladder malignancy and other late sequelae of therapy must be carefully weighted against the curative gains provided by cyclophosphamide. Moreover, long-term side effects of therapy that might be acceptable in cancer treatment may need to be re-evaluated for patients with non-neoplastic disorders.
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