Removal of famotidine by haemodialysis in elderly anuric patients

From Physical Pharmacy to Clinical Pharmacology

Research works on molecular interactions in solutions were carried out at School of Pharmacy, the University of Wisconsin under the direction of Prof. T. Higuchi and at Faculty of Pharmaceutical Sciences, Kyoto University under the direction of Prof. H. Sezaki. Studies on permeation of drugs through polymer membranes were carried out at Faculty of Pharmacy and Pharmaceutical Sciences, University of Alberta, Edmonton, Canada and at Pharmaceutical Chemistry Research Laboratories at Food and Drug Directorate, Department of Health and Welfare, Canada. Studies on modification of delivery patterns by means of pharmaceutical approaches were carried out at Faculty of Pharmaceutical Sciences, Hokkaido University. Topics related to modification of drug delivery patterns include employment of amorphous forms such as ground mixture with micro-crystalline cellulose and coprecipitate with polyvinylpyrrolidone, use of biodegradable polymers such as polylactic acid and polycarbonates, gel-forming materials such as konjac, agar and hydroxypropylcellulose, and physicochemical systems such as complexation. Works related to drug delivery and disposition of drugs in humans were carried out at Department of Pharmacy, Kumamoto University Hospital. Topics related to drug delivery in humans include injections containing anticancer drugs for intra-arterial administration, lidocaine gels for dermal anesthesia, glucagon solution for nasal administration. Topics related to disposition of drugs in humans include clinical pharmacokinetic studies in infants and elderly and medical uses of adsorbents.

Pharmacokinetic optimisation of the treatment of peptic ulcer in patients with renal failure

The pathogenesis of peptic ulceration is not yet clear. It could be due to an imbalance between acid secretion and mucosal defensive and/or protective mechanisms, but the association between Helicobacter pylori and peptic ulceration has questioned this hypothesis. Therefore, drugs inhibiting acid secretion and/or eradicating H. pylori are of major interest. Peptic ulcer disease is often associated with renal failure. For the selection of the proper dosage of these agents their pharmacokinetic properties and alterations in pharmacokinetics in various disease states, including renal failure, should be known. As histamine H2-receptor antagonists and pirenzepine are mainly eliminated by the renal route their elimination is dependent on creatinine clearance. Consequently, their elimination will be impaired in patients with renal insufficiency, which makes dosage reduction mandatory in these patients. No dosage supplementation is necessary after any type of dialysis because the drugs are removed in insignificant amounts by the various blood purification procedures. Misoprostol and proton pump inhibitors, such as omeprazole, lansoprazole and pantoprazole, are primarily eliminated by nonrenal routes. Therefore no dosage adjustments are necessary in patients with renal insufficiency. Bismuth salts, sucralfate and antacids should be avoided in patients with renal failure because of the accumulation of their cations and the associated risk of toxic reactions. For most agents more long term experience from comparative and double-blinded studies is needed to define better their clinical efficacy and tolerability in patients with renal failure.

Pharmacokinetics and pharmacodynamics of H2-receptor antagonists in patients with renal insufficiency

H2-receptor antagonists are frequently used in patients with renal insufficiency to treat hyperacidity and resultant peptic ulceration. All H2-antagonists are mainly eliminated by the renal route (glomerular filtration and tubular secretion). Since it is dependent on creatinine clearance (CLCR), elimination will be impaired in renal insufficiency. Protein binding and volumes of distribution (Vd) of H2-antagonists are not significantly altered in patients with renal impairment. Bioavailability (F) is similar in patients with and without renal insufficiency, except for nizatidine, which has an F that is lower in uraemic patients. When given in similar doses, mean peak concentrations (Cmax) and area under the concentration-time curve (AUC) are higher in patients with renal insufficiency than in those with normal renal function. Thus, maintenance doses of H2-antagonists should be reduced in line with reductions in CLCR. The time to reach Cmax is similar for all drugs except ranitidine, which has a delayed Cmax. Due to the decreased renal clearance (CLR), elimination half-life (t1/2) is prolonged 3- to 8-fold depending upon the degree of renal failure and the particular drug. H2-antagonists are removed by various dialysis procedures in insignificant amounts. Thus, no dosage supplementation is necessary after any type of dialysis therapy. By means of intragastric long term pH-metry it has been shown that inhibition of gastric acid secretion is prolonged in patients with renal insufficiency.