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OPEN ACCESS PLUS
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Contents
8(2): Pp. 135 - 155
Philipp Y. Maximov, Theresa M. Lee and V. Craig Jordan
[Open Access Plus] |
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Selective estrogen receptor modulators (SERMs) are structurally different compounds that interact with intracellular estrogen receptors in target organs as estrogen receptor agonists or antagonists. These drugs have been intensively studied over the past decade and have proven to be a highly versatile group for the treatment of different conditions associated with postmenopausal women’s health, including hormone responsive cancer and osteoporosis. Tamoxifen, a failed contraceptive is currently used to treat all stages of breast cancer, chemoprevention in women at high risk for breast cancer and also has beneficial effects on bone mineral density and serum lipids in postmenopausal women. Raloxifene, a failed breast cancer drug, is the only SERM approved internationally for the prevention and treatment of postmenopausal osteoporosis and vertebral fractures. However, although these SERMs have many benefits, they also have some potentially serious adverse effects, such as thromboembolic disorders and, in the case of tamoxifen, uterine cancer. These adverse effects represent a major concern given that long-term therapy is required to prevent osteoporosis or prevent and treat breast cancer. The search for the ‘ideal’ SERM, which would have estrogenic effects on bone and serum lipids, neutral effects on the uterus, and antiestrogenic effects on breast tissue, but none of the adverse effects associated with current therapies, is currently under way. Ospemifene, lasofoxifene, bazedoxifene and arzoxifene, which are new SERM molecules with potentially greater efficacy and potency than previous SERMs, have been investigated for use in the treatment and prevention of osteoporosis. These drugs have been shown to be comparably effective to conventional hormone replacement therapy in animal models, with potential indications for an improved safety profile. Clinical efficacy data from ongoing phase III trials are available or are awaited for each SERM so that a true understanding of the therapeutic potential of these compounds can be obtained. In this article, we describe the discovery and development of the group of medicines called SERMs. The newer SERMs in late development: ospemifene, lasofoxifene, bazedoxifene, are arzoxifene are described in detail.
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4(2): Pp. 126 - 131
Noboru Kaneko, Ryuko Matsuda, Yoshihito Hata and Ken Shimamoto
[Open Access Plus] |
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K201 is a 1,4-benzothiazepine derivative that is a promising new drug with a strong cardioprotective effect. We initially discovered K201 as an effective suppressant of sudden cardiac cell death due to calcium overload. K201 is a nonspecific blocker of sodium, potassium and calcium channels, and its cardioprotective effect is more marked than those of nicorandil, prazosine, propranolol, verapamil and diltiazem. Recently, K201 has also been shown to have activities indicated for treatment of atrial fibrillation, ventricular fibrillation, heart failure and ischemic heart disease, including action as a multiple-channel blocker, inhibition of diastolic Ca2+ release from the sarcoplasmic reticulum, suppression of spontaneous Ca2+ sparks and Ca2+ waves, blockage of annexin V and provision of myocardial protection, and improvement of norepinephrine-induced diastolic dysfunction. Here, we describe the pharmacological characteristics and clinical applications of K201.
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3(3): Pp. 198 - 203
Stefan Pursche, Eberhard Schleyer, Malte von Bonin, Gerhard Ehninger, Samir Mustafa Said, Roland Prondzinsky, Thomas Illmer, Yanfeng Wang, Christian Hosius, Zariana Nikolova, Martin Bornhauser and Gregor Dresemann
[Open Access Plus] |
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Background: Imatinib mesylate is used in combination with hydroxyurea (HU) in ongoing clinical phase II studies in recurrent glioblastoma multiforme (GBM). CYP3A4 enzyme-inducing antiepileptic drugs (EIAEDs) like carbamazepine, phenytoin, and oxcarbazepine - as well as non-EIAEDs like valproic acid, levetiracetam, and lamotrigine - are frequently used in patients with GBM. Since CYP3A4 is the major isozyme involved in the metabolism of imatinib, we investigated the influence of EIAEDs on imatinib pharmacokinetics (pk). Methods: GBM patients received 600 mg imatinib p.o./o.d. in combination with 1.0 g HU p.o./o.d..together with either EIAEDs, non-EIAEDs, or no antiepileptic drug (non-AEDs) comedication. Trough plasma levels of imatinib and its active main metabolite N-desmethyl-imatinib (CGP74588) were determined biweekly in these patients, total 543 samples being collected from 224 patients (up to 6 times / patient). All three groups were compared to each other and with historical pharmacokinetic data obtained from patients with chronic myeloid leukemia (CML). Results: Mean imatinib trough levels in patients not receiving AEDs ( 1404 ng/ml, CV 64%) and on non-EIAEDs (1374 ng/ml, CV 46%) were comparable with mean imatinib trough levels of the historical control group of CML patients (1400 ng/ml, CV 50%). Mean trough levels of imatinib were reduced up to 2.9-fold (477 ng/ml, CV 70%) in patients treated with EIAEDs. Only slight, but although significant differences were observed in the mean trough level of the metabolite CGP74588 between EIAED-, non-EIAED and no-AED patients, 240 ng/ml (CV 57%) , 351 ng/ml (CV 34%) and 356 ng/ml (CV 52%), respectively. The corresponding mean level for CML patients was 300 ng/ml (CV 50%). Conclusion: Significant decreases of imatinib and CGP74588 trough levels were observed for patients receiving EIAEDs. The EIAED-induced reduction in trough imatinib levels can be avoided by switching to non-EIAEDs comedication or compensated by administering higher imatinib doses. In addition these data demonstrate that there is no significant difference in the pharmacokinetics of imatinib between patients with glioblastoma and CML.
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2(3): Pp. 234 - 243
Soo-Peang Khor and Ann Hsu
[Open Access Plus] |
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Levodopa , a prodrug of dopamine, remains to be one of the main drugs in the treatment of Parkinsons disease. All current levodopa products are formulated with aromatic amino acid decarboxylase inhibitors such as carbidopa or benserazide to prevent the metabolism of levodopa in the gastrointestinal tract and systemic circulation. Levodopa pharmacokinetic profiles remain unchanged after multiple doses, and are similar between healthy volunteers and patients and among patients at different stages of disease. Entacapone inhibits the metabolism of levodopa therefore increases the area under the plasma concentration-time profile of levodopa; however, it may decrease the initial absorption rate of levodopa in some patients probably due to competitive absorption. Food appears to affect the absorption of levodopa, but its effects vary with formulations. The results of positron emission tomography study suggest that a high protein diet may compete with the uptake of levodopa into the brain, therefore, may result in reduced levodopa effects. Since infusion studies demonstrated that it is beneficial to maintain stable plasma concentrations of levodopa, controlled-release formulations have been designed to provide prolonged absorption of levodopa. However, subsequent pharmacokinetic and pharmacodynamic studies demonstrated that a threshold concentration of levodopa appears to be necessary to switch patients “on”. Once patients are turned “on”, the duration of levodopa effects may be correlated with plasma concentration of levodopa. As such, more recent studies have demonstrated significant clinical benefits such as shorter time to “on” and longer duration of “on” when combining the immediate- and controlled-release levodopa products as compared to controlled-release levodopa products. Given these findings, it is important for physicians to understand the relationship between the pharmacokinetics and pharmacodynamics of levodopa in order to provide dosage regimens that meet patient needs. The pharmacokinetics and pharmacodynamics data of levodopa reported in the literature are reviewed here.
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2(2): Pp. 145 - 153
Xin-Sheng Deng and Richard A. Deitrich
[Open Access Plus] |
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Ethanol (EtOH) in alcoholic beverages is consumed by a large number of individuals and its elimination is primarily by oxidation. The role of nitric oxide (NO) in EtOHs effects is important since NO is one of the most prominent biological factors in mammals. NO is constantly formed endogenously from L-arginine. Dose and length of EtOH exposure, and cell type are the main factors affecting EtOH effects on NO production. Either acute or chronic EtOH ingestion affects inducible NO synthase (iNOS) activity. However it seems that EtOH suppresses induced-NO production by inhibition of iNOS in different cells. On the other hand, it is clear that acute low doses of EtOH increase both the release of NO and endothelial NOS (eNOS) expression, and augment endothelium-mediated vasodilatation, whereas higher doses impair endothelial functions. EtOH selectively affects neuronal NOS (nNOS) activity in different brain cells, which may relate to various behavioral interactions. Therefore, there is an excellent chance for EtOH and NO to react with each other. Effects of EtOH on NO production and NOS activity may be important to EtOH modification of cell or organ function. Nitrosated compounds (alkyl nitrites) are often found as the interaction products, which might be one of the minor pathways of EtOH metabolism. NO also inhibits EtOH metabolizing enzymes. Furthermore, NO is involved in EtOH induced liver damage and has a role in fetal development during EtOH exposure in pregnancy. The mechanisms underlying these effects are only partially understood. Hence, the current discussion of the interaction of EtOH and NO is presented.
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