Impact of ABO blood groups on tirofiban mediated inhibition of platelet function.

Previous investigations revealed that ABO blood groups are associated with divergent concentrations of several coagulation factors. Concentrations of von Willebrand factor (vWF) and factor VIII are lower in individuals with blood group O as compared to subjects with blood group A, B or AB which might result in a reduced inhibition of platelet aggregation. The aim of the present in-vitro-investigation was to elucidate the impact of ABO blood group dependent vWF concentrations on tirofiban mediated inhibition of GPIIb/IIIa function. Platelet function was measured with the platelet function analyzer PFA-100 at baseline and at increasing concentrations of tirofiban and stratified for blood group O vs. A. If measured with the collagen/epinephrine cartridge, blood group O was associated with a prolonged mean baseline closure time in comparison with blood group A (175.8 +/- 64.9 s vs. 121.4 +/- 33.4 s, p = 0.037) which was paralleled by reduced concentrations of vWF and factor VIII. In contrast, no differences in closure time (227.6 +/- 76.1 s vs. 223.9 +/- 81.9 s, p = 0.96) could be found in the presence of tirofiban (0.1 microg/ml). Thus, tirofiban mediated GP IIb/IIIa receptor antagonism as determined with the PFA-100 seems to be independent on plasma concentration of vWF.

[Drug therapy of elderly patients from the viewpoint of the clinical pharmacologist]. / Arzneimitteltherapie im Alter aus der Sicht des klinischen Pharmakologen.

Polypragmasy (polypharmacotherapy) is often due to the frequent incidence of multimorbidity among elderly patients. This may evoke unpredictable drug-interactions, which often become a reason for hospitalization. Additional medications might be the consequence. Geriatric patients are often characterized by variant pharmacokinetic parameters. Individualized drug-therapy should take into consideration not only the patients' age, liver and kidney functions but also the individual variability of hepatic metabolization and drug-resorption in the intestine based on genetic polymorphisms. Summing up, it is very important to verify a consisting or a new drug-therapy concerning its risk-benefit ratio and if it is needed, to omit or change some of the medications.

[Drug therapy in the old age. Drug effects in the elderly]. / Arzneimitteltherapie im Alter. Misten Sie die Pillendöschen aus!

The frequency of multimorbidity in elderly patients may mislead the physician into practicing polypragmasy (polypharmacy), resulting in unpredictable drug interactions. Such interactions are a quite common cause of hospitalization in geriatric patients. Pharmacokinetics are often altered in the aged, and individualized medication should take into consideration not only the patient's age, liver and kidney function, but also the individual variability of hepatic metabolism and drug absorption from the gastrointestinal tract dictated by genetic polymorphism. Drug treatment in the elderly should always be carefully assessed as to its risks and benefits, and, where indicated, certain medications should be replaced by or omitted.

Mechanism of block by 4-aminopyridine of the transient outward current in rat ventricular cardiomyocytes.

The effects of 4-aminopyridine (4-AP) on the transient outward current (I(to)) were investigated in rat ventricular cardiomyocytes at different values of intracellular pH (pHi) and extracellular pH (pHo). The 4-AP was administered either extracellularly (bath application) or intracellularly (diffusion from the intrapipette solution). The 4-AP diminished I(to) given either from inside or outside the cell membrane. The block by extracellularly applied 4-AP (4-APo) of the peak amplitude of I(to) was decreased by external acidification but increased by external alkalinization; conversely, the block by 4-APo was decreased by internal alkalinization but increased by internal acidification. Intracellularly applied 4-AP (3 mM) was more effective at low pHi. Because 4-AP is a tertiary amine and exists in protonated and unprotonated forms, these results are in agreement with the assumption that one major mechanism for 4-AP to block I(to) is to penetrate the cell membrane in its uncharged form and to reach intracellular binding sites in its protonated form.