curves for ( 3 H) ramiprilat were established on each tissue with the converting enzyme inhibitors, and their potencies were expressed as the concentration that inhibited 50% of the specific ( 3 H) ramiprilat binding. In the plasma, lung, and heart, the order of activities was: ramiprilat >enalaprilat> captopril > ramipril > enalapril. This order was different in the kidney (cortex and medulla): ramiprilat>enalaprilat>ramipril>captopril>enalapril. For ramiprilat, enalaprilat, and captopril, there were no differences in their respective potencies between tissues or between rat strains. However, the two prodrugs ramipril and enalapril were 10-30 times more active in the kidney than in the other tissues in both groups of rats. This was due to the deesterification of the prodrugs: in the presence of an esterase inhibitor (diethyl nitrophenyl phosphate, 10 /AM), the potencies of ramipril in the kidney were not different from that obtained in the lung, which was not affected by the presence of the esterase inhibitor. These results suggest that the variations in the tissue activities of an angiotensin converting enzyme inhibitor are probably not due to differences in tissue affinities of the angiotensin converting enzyme inhibitor but depend on the concentration of this angiotensin converting enzyme inhibitor in each tissue. (Hypertension 1991;17:492-496)

La non-prise en compte de la mauvaise observance induit forcement un traitement non optimal.

Que ce soit avant ou après sa mise sur le marché, le risque d’effet indésirable d’un médicament est évalué selon deux approches.

The environment of drug safety is changing. In addition to the current system of pharmacovigilance based on spontaneous report of adverse events, clinical data observed in a given patient with a given symptom is taken into consideration and compared with information coming from pharmacovigilance data bases, which is then analyzed for causality by the experts of both the promotor and the public network. Such information is integrated into a risk management strategy, defined together by the French drug agency (Afssaps) and the marketing authorization holder. This strategy includes a pharmacovigilance plan and, if possible, a risk minimisation plan.

Adverse drug effects are more frequent in elderly patients, especially with drugs that have small safety margins. This is the case of many cardiovascular drugs. Patients who are frail, owing to their age and their psychomotor, nutritional and social stratus, are particularly at risk. Two pharmacokinetic factors appear to be of major concern, namely the age-related decrease renal function and changes in drug metabolism and distribution. Renal function is probably the single factor most responsible for altered drug levels in the elderly. The normal age-related decrease in creatinine clearance can lead to the accumulation of drugs that are normally excreted by the kidneys without being inactivated Dose adjustment of such drugs is usually based on the Cockcroft-Gault formula of creatinine clearance. Changes in hepatic metabolism and drug distribution are less commonly taken into account. The avoidance of drug toxicity requires familiarity with the medications prescribed and particular vigilance for signs of adverse effects.

Adverse drug reactions (ADRs) have been recognised as an important cause of hospital admission. Most of these drug-related admissions were expected ADRs and, thus, partly preventable. However, as far as we know, the assessment of the preventability of ADRs was addressed in only two studies performed in France. In contrast, several other studies have been performed, mainly in the USA, and using different methods of assessing preventability. None of these methods were clearly evaluated with regard to reproducibility, validity or relevance. The purpose of this study was to initiate the validation of a French preventability scale. Here, we propose the first two phases of validation: the content validity and reliability of the scale. A working group of pharmacovigilance experts has been specifically established for this purpose. The content validity was assessed by collecting items representative of preventability. The choice and the formulation of items and a proposal of a score (global and for each item) were adopted after the consensus of the experts. A definitive version of the ADR preventability scale was used for the assessment of reliability. During the second phase, experts independently tested the new scale from observations of ADRs (49 central nervous system haemorrhages with antivitamine K). The concordance of the experts' judgements was calculated using two statistical methods (Kappa statistic and correlation coefficient). The content validity phase was performed during several workshops where experts discussed the choice and formulation of the best items. We decided to construct a scale with a small number of items, allowing a rapid evaluation of the preventability of ADRs. On the basis of a global score, four categories of preventability of ADRs ("preventable", "potentially preventable", "unclassable", "not preventable" ADRs) were proposed. The agreement of experts regarding the global score was low, with a poor correlation coefficient value (coefficient interclass = 0.491). Classification of ADRs in the four categories by the experts showed discrepancies (Kappa = 0.1136). The preventability assessment using this scale was feasible, although poor concordance between the judges has raised some questions. Several experts found use of this scale difficult in terms of a clear understanding of the items, and found that two of them were redundant. We have oversimplified some items and revision of their formulation will be necessary. Moreover, most of ADR notifications were poorly documented, resulting in a frequent choice of an "unevaluable" item. This represented an important bias in the calculation of the global score. This experience suggests the need for further studies to improve this French ADR preventability scale and validate it in differing circumstances, in order to provide a useful tool to enhance the rational use of drugs.

Comparison of variances can be useful in assessing the regularity of drug effects. In order to compare the variances of the saluretic effects of piretanide and frusemide, two loop diuretics with different bioavailabilities, a double-blind cross-over study was carried out in 34 normal volunteers. The diuretics were given in randomized order, with an interval of 7 days, in single equipotent doses (frusemide 6.25 mg and piretanide 1.0 mg chosen from previous results) adjusted by body weight. The dispersion of individual values (comparison of variances from paired measures) for Na+, Cl− and Ca++ excretion, urine osmolality and excretion of the drugs, was significantly smaller for piretanide than for frusemide. It is concluded that the saluretic effect of a single dose of piretanide varies less than that of an equipotent dose of frusemide. The methodology may be useful in trials of drugs for which regularity of effect is important.

L’efficacité de la prévention d’un risque médicamenteux dépend de la précision avec laquelle ses facteurs déclenchants ou favorisants sont connus et de la qualité de l’information donnée à son sujet aux prescripteurs et aux utilisateurs. L’identification d’un risque devrait mettre à profit l’ensemble des données précliniques et cliniques disponibles pour la spécialité pharmaceutique considérée et les confronter aux données existantes pour des médicaments partageant un même mode d’action ou une même stratégie thérapeutique. L’information doit s’appuyer sur un plan de communication adapté au contexte de la pathologie traitée, des alternatives thérapeutiques existantes et du bénéfice attendu.

Objectives: To analyze, in acute renal failure (ARF) in diabetic rats, how moderate functional ARF would modify metformin (MET) pharmacokinetics and if plasma and renal tissue MET accumulation could aggravate renal insufficiency and/or elicit plasma lactate accumulation.Methods: Streptozotocin-induced diabetic rats were allocated to four groups: control, MET, ARF, ARF-MET (6-7 rats per group). MET (100 mg/kg/day) was given per os for two weeks before ARF was induced by drinking restriction and enalapril treatment. The effects of MET and/or ARF were examined in vivo on renal function in conscious rats (metabolic cages) and ex vivo on renal vascular reactivity (isolated kidney).Results: MET treatment (plasma level: 5.3 +/- 1.4 mug/ml, mean +/- SEM), resulted in biguanide accumulation in cortex and medulla (53 17 and 80 +/- 40 mug/g respectively). MET was devoid of any effect on creatinine clearance, mean blood pressure or renal vascular resistance, but moderately increased plasma lactate (3.8 +/- 0.5 vs 3.2 +/- 0.2 mM, P < 0.05) and decreased angiotensin II-induced renal vasoconstriction. ARF, although mild, decreased renal MET clearance (0.29 +/- 0.05 vs 1.01 +/- 0.31 ml/min/100 g, P < 0.05) and increased plasma and renal tissue MET levels (x 2-4). MET however did not worsen the fall in glomerular filtration rate, nor modify renal vascular reactivity. ARF did not change the MET-elicited moderate increase in plasma lactate.Conclusion: Despite the increase in MET plasma and renal tissue levels subsequent to moderate ARF, no harmful metabolic effect on plasma lactate and no further impairment of renal function was observed in MET-treated diabetic rats subjected to ARF.

Spironolactone, a diuretic antagonist of aldosterone has an unexplained side effect of amenorrhea which could be due to an angiogenesis inhibition. In this study we compared the effects of spironolactone, canrenone an active metabolite of spironolactone and eplerenone a more selective mineralocorticoid antagonist in rats implanted with a fibrin gel chamber. Perforated plexiglass chambers filled with rat fibrin, spironolactone (50 microM), canrenone (100 microM), eplerenone (500 microM), DMSO (0.05%) and control were implanted into the dorsal subcutaneous space of wistar rats. After 14 days of implantation, an invasion of the fibrin gel chamber by neovascularised buds had occurred through the holes. The number of vessels in the central field and in two or three peripheral fields covering the surface of the bud, were measured for each drug tested and compared to the control. In spironolactone treated chambers, the numbers of peripheral and central vessels were significantly reduced compared to control (p < 0.001). Canrenone, eplerenone and DMSO did not reduce the number of vessels (m +/- ESM, ANOVA followed by Newman-Keuls test). Spironolactone but not canrenone, nor eplerenone inhibited vessels formation in vivo. This antiangiogenic activity appeared to be not related to the antimineralocorticoid effect of spironolactone.

Spironolactone, a diuretic antagonist of aldosterone has an unexplained side effect of amenorrhea which could be due to an angiogenesis inhibition. In this study we compared the effects of spironolactone, canrenone an active metabolite of spironolactone and eplerenone a more selective mineralocorticoid antagonist in rats implanted with a fibrin gel chamber.Perforated plexiglass chambers filled with rat fibrin, spironolactone (50muM), canrenone (100muM), eplerenone (500muM), DMSO (0.05%) and control were implanted into the dorsal subcutaneous space of wistar rats. After 14 days of implantation, an invasion of the fibrin gel chamber by neovascularised buds had occurred through the holes. The number of vessels in the central field and in two or three peripheral fields covering the surface of the bud, were measured for each drug-tested and compared to the control.In spironolactone treated chambers, the numbers of peripheral and central vessels were significantly reduced compared to control (p<0.001). Canrenone, eplerenone and DMSO did not reduce the number of vessels (m+/-ESM, ANOVA followed by Newman-Keuls test).Spironolactone but not canrenone, nor eplerenone inhibited vessels formation in vivo. This antiangiogenic activity appeared to be not related to the antimineralocorticoid effect of spironolactone.

This study was designed to determine the involvement of AT(1) receptors in the uptake of ANG II in the kidney of rats exposed to differing salt intake. Male Wistar-Kyoto rats were treated with a normal-salt (NS; 1% NaCl, n = 7) or a low-salt (LS; 0.025% NaCl, n = 7) diet combined with (LS+Los, n = 7; NS+Los, n = 7) or without losartan (30 mg. kg(-1). day(-1)), an AT(1) receptor antagonist. Renin (RA) and angiotensin-converting enzyme (ACE) activities and angiotensinogen, ANG I, and ANG II levels were measured in plasma, renal cortex, and medulla. In LS rats, in both plasma and renal cortex, the increase in RA was associated with an increase in ANG I and ANG II levels compared with NS rats, but intrarenal ANG II levels increased more than ANG I levels. In NS+Los rats, the increase in RA in plasma was followed by a marked increase in plasma ANG I and ANG II levels compared with NS rats whereas in the kidney the increase of renal RA was followed by a decrease of the levels of these peptides. The same pattern was observed in LS+Los rats, but the decrease in renal ANG II levels was much more pronounced in LS+Los rats than in NS+Los rats. Our results suggest that the increase in renal ANG II levels after salt restriction results mainly from an uptake of ANG II, via AT(1) receptors. Such elevated intrarenal ANG II levels could contribute to maintain sodium and fluid balance and arterial blood pressure during salt-deficiency states.

Angiogenesis requires endothelial cell proliferation and their vascular rearrangement. A report of inhibiting effect of spironolactone on smooth muscle cell proliferation led us to study in vitro the effects of this drug on the endothelial cell proliferation and migration. Spironolactone (10 to 100 microM) and one of its active metabolite, canrenone (10 to 100 microM), are added to human umbilical vein endothelial cells (HUVEC). Their effect on cellular proliferation is evaluated by measuring the amount of the cellular nucleic acids using a fluorometric assay (CyQuant). Cell migration is measured using a multiwell chamber assay (Transwell). In further experiments, we investigated their effect on the capillary-like tube formation in vitro generated by HUVEC seeded in a three-dimensional biological gel (Matrigel). The VEGF (10 ng/mL) and the bFGF (10 ng/mL) were used as mitotic and cell differentiation factors. Effect on cell cycle distribution is investigated by flow cytometry analysis. Spironolactone inhibits HUVEC proliferation but canrenone does not have any significant effect. The growth promoters VEGF or bFGF do not modify inhibiting effect of spironolactone. Spironolactone (50 microM) and canrenone (50 microM) are without effect on cell migration. Capillary-like networks on Matrigel is not modified by spironolactone or canrenone. Spironolactone inhibits progression through S phase of the cell cycle. Spironolactone inhibits the proliferation of the endothelial cells in vitro but shows no effect on their migration and their rearrangement in capillary-like structures. These data should be confirmed in models of angiogenesis in vivo.