[Clinical assessment of drug safety]. / Sécurité d'emploi des médicaments: évaluation clinique.

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.

Renal function in patients with obstructive sleep apnea. Effects of nasal continuous positive airway pressure.

Patients with obstructive sleep apnea (OSA) often exhibit nocturnal polyuria, which disappears with nasal continuous positive airway pressure (CPAP) treatment. We measured water and electrolyte urinary excretion, creatinine and osmolal clearances, and water transport during sleep in 13 polygraphically monitored patients with OSA during two consecutive nights, either untreated or treated with nasal CPAP, and in eight normal subjects. Untreated patients with OSA had greater urinary flows and greater urinary sodium, chloride, and potassium excretions than did controls. Nasal CPAP treatment in patients with OSA resulted in a reduction in urinary flow and in sodium and chloride excretion, with a concomitant increase in sodium resorption. None of these effects was observed in CPAP-treated normal subjects. The only effect of nasal CPAP common to normal subjects and patients was a trend toward decreased glomerular filtration rate.

In vitro tissue potencies of converting enzyme inhibitors. Prodrug activation by kidney esterase.

The inhibition of angiotensin converting enzyme by ramipril, ramiprilat, enalapril, enalaprilat, and captopril was studied in the plasma and various tissues (lung, heart, renal cortex, renal medulla) of normotensive rats and spontaneously hypertensive rats. Displacement curves for [3H]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 [3H]ramiprilat binding. In the plasma, lung, and heart, the order of activities was: ramiprilat greater than enalaprilat greater than captopril greater than ramipril greater than enalapril. This order was different in the kidney (cortex and medulla): ramiprilat greater than enalaprilat greater than ramipril greater than captopril greater than 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 microM), 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.

Brain mineralocorticoid receptor control of blood pressure and kidney function in normotensive rats.

Brain mineralocorticoid receptors appear to contribute to mineralocorticoid hypertension and may be involved in blood pressure control in normotensive rats. We examined the effect of blockade of central mineralocorticoid receptors with the use of a selective antagonist (RU28318) on cardiovascular and renal function in conscious normotensive rats. The contribution of renal innervation was evaluated in rats with bilaterally denervated kidneys. Young adult, male Wistar rats were trained for systolic blood pressure measurement by a tail sphygmographic method and accustomed to metabolic cages for collection of urine. One week before experimentation, an intracerebroventricular cannula was implanted. Systolic blood pressure was diminished 30 minutes after an intracerebroventricular dose of 10 ng of RU28318. The effect was maximal at 8 hours and was still present after 24 hours. Blood pressure returned to the basal level by 48 hours. During the period 0 to 8 hours after intracerebroventricular injection, rats treated with the antagonist showed an increase in diuresis and urinary electrolyte excretion. No significant effect on plasma renin activity, measured 8 and 30 hours after administration of RU28318, was observed. In denervated rats, the decrease in systolic blood pressure after administration of RU28318 was reduced. The difference was statistically significant compared with controls at 2 hours but not at 8 hours, and blood pressure returned to the basal value by 24 hours. The increases in diuresis and urinary electrolyte excretion induced by RU28318 were abolished in denervated rats. These results show that brain mineralocorticoid receptors are involved in blood pressure regulation and kidney function homeostasis in conscious normotensive rats. The renal nerves appear to participate in the brain mineralocorticoid receptor control of blood pressure.

Angiotensin converting enzyme variability in hypertensive and normotensive rats.

Recent data have revealed biological and genetic variability in normotensive Wistar-Kyoto rats, which are considered to be the most appropriate control strain for spontaneously hypertensive rats. To investigate the possibility that angiotensin converting enzyme activity could be affected by this variability, we measured plasma and tissue (lung, heart, renal cortex, renal medulla, and adrenal gland) angiotensin converting enzyme activity in spontaneously hypertensive rats and normotensive Wistar-Kyoto rats from three commercial suppliers in France: Iffa-Credo, Janvier, and Charles River Laboratories. Angiotensin converting enzyme activity was measured in vitro with a fluorometric assay using carbobenzoxy-Phe-His-Leu as substrate. Angiotensin converting enzyme activity in both rat strains varied considerably from one supplier to another, and therefore, comparisons of spontaneously hypertensive rats and Wistar-Kyoto rats from the different suppliers produced conflicting results. For Wistar-Kyoto rats, angiotensin converting enzyme activity in the plasma, heart, kidney, and adrenal glands was highest in rats from Iffa-Credo and lowest in rats from Charles River. For spontaneously hypertensive rats, angiotensin converting enzyme activity in the plasma and tissues was highest in rats from Janvier, whereas no difference could be observed between rats from Iffa-Credo and Charles River. These data confirm the problem of how to interpret and compare studies that use spontaneously hypertensive and Wistar-Kyoto rat strains.

Effect of captopril on intrarenal blood flow.

The inhibition of the renin-angiotensin system by captopril was used in pentobarbital-anesthetized dogs to confirm that the vasoconstrictive action of endorenally synthesized angiotensin II predominates on the efferent glomerular arteriole. Ozolinone is a loop diuretic with two isomers. Only (-)- ozolinone is diuretic, whereas both isomers have a renal vasodilatory effect which predominates on the efferent glomerular arteriole. Only the diuretic isomer increases renin release. The renin hypersecretion is simultaneous with recovery from the initial fall in filtration fraction, because of postglomerular vasodilatation. This recovery does not occur with (+)- ozolinone and is inhibited by pretreatment with captopril. This confirms that vasoconstrictive action of angiotensin II predominates on the efferent glomerular arteriole. Such a vasoconstrictive effect might affect blood flow in the vasa recta, which arise from the efferent arterioles of juxtamedullary glomeruli. This action might enable the renin-angiotensin system to participate in the control of renal medullary blood flow and urinary concentration.

Plasma renin activity and changes in tissue angiotensin converting enzyme.

OBJECTIVES: Recent evidence suggests that tissue generation of angiotensins I and II depends on the level of the plasma components of the renin-angiotensin system and on tissue-specific processes. The present study was undertaken to clarify the possible relationship between plasma renin activity (PRA) and tissue angiotensin converting enzyme (ACE) activity in the heart, lung, kidney cortex and kidney medulla of Wistar-Kyoto rats. In the kidney cortex particular attention was focused on renal brush-border ACE. METHODS: Different experimental models known to have opposite effects on PRA were used: changes in salt intake, deoxycorticosterone acetate (DOCA) with or without salt supplements, and the Goldblatt two-kidney, one clip (2-K,1C) model. Two weeks after the start of the experiments the rats were killed, and PRA, and plasma and tissue ACE activity, were measured. RESULTS: At the end of the study the blood pressure in the treated rats was not significantly different from control. As expected, the PRA were highest in the 2-K,1C and depleted-salt groups and lowest in the DOCA, DOCA-salt and high-salt groups. ACE responses were different in different types of tissue, with no relationship between PRA and plasma or tissue ACE activity. For example, DOCA treatment led to increased ACE activity in the heart and the kidney only if the rats were maintained on a high salt intake. DOCA or salt alone failed to have this effect. In the 2-K,1C model the unclipped kidneys did not show any significant variation in ACE activity, but the clipped kidneys exhibited increased ACE activity compared with sham-operated rats. This increase, coupled with increased renal renin secretion, could play a role in the acceleration of local angiotensin II formation, and could thus initiate and sustain the development of hypertension in this model. CONCLUSION: The present results show that variations in ACE activity were organ-specific and were not linked either to hypertension or to changes in PRA.

Age-related variations in tissue angiotensin converting enzyme activities: comparison between spontaneously hypertensive and Wistar-Kyoto rats.

Angiotensin converting enzyme (ACE) activity was measured by fluorimetry in the plasma, lung, heart, aorta and kidney (cortex and medulla) of 3-, 5-, 8- and 11-week-old spontaneously hypertensive rats (SHR) and compared with that of age-matched Wistar-Kyoto rats (WKY). In the plasma, lung and kidney (cortex and medulla), ACE activity was lower in SHR than in WKY. This was evident as early as the age of 3 weeks. In contrast, there were no differences between SHR and WKY in the aorta and the heart. Age-related variations in ACE activities differed in each tissue and in both groups of rats, but no major modifications were correlated with the development of hypertension. A binding assay was performed with [3H]ramiprilat; affinity (KD) and the maximum number of binding sites (Bmax) were determined in plasma and tissues of 3-week-old SHR and WKY. The KD values were identical in the two groups but Bmax was lower in all SHR tissues except in the heart; these results might be related to the decrease in ACE activity. Our results probably reflect genetic differences in ACE activity between SHR and WKY, and suggest that ACE regulatory mechanisms act differently in each tissue.

Ramipril-induced decrease in renal lithium excretion in the rat.

1. The interaction of ramipril, an inhibitor of angiotensin I converting enzyme, with renal lithium handling was analysed in conscious normotensive Wistar rats and compared with the known increase in renal tubular lithium reabsorption induced by the non-steroidal anti-inflammatory drug, indomethacin. 2. The rats were treated for five days with ramipril (1 mg kg-1 day-1 orally), indomethacin (2.5 mg kg-1 day-1 intramuscularly) or their solvents. Lithium chloride (16.7 mg kg-1 intraperitonealy) was given as a single dose on the fifth day and renal functions were measured. 3. Ramipril induced a decrease in renal lithium clearance which was correlated with the decrease in the quantity of filtered lithium and the increase in the tubular fractional reabsorption of the metal. Ramipril also reduced the systolic blood pressure of the rats by about 15 mmHg. 4. In the absence of any effect on creatinine clearance or systolic blood pressure, indomethacin increased renal fractional lithium reabsorption and led to an increase in plasma lithium levels, as previously reported by our group. 5. In conclusions, our results indicate that ramipril decreases renal lithium excretion in Wistar rats, when given orally at a dose of 1 mg kg-1 day-1 over five days.

Absence of a losartan interaction with renal lithium excretion in the rat.

1. The interaction of losartan, a non-peptide specific AT1 receptor antagonist with the renal handling of lithium was analysed in conscious normotensive Wistar rats and compared with the known increase in renal tubular lithium reabsorption induced by the non-steroidal anti-inflammatory drug, indomethacin. 2. The rats were treated for five days with losartan (10 mg kg-1 day-1, orally), indomethacin (2.5 mg kg-1 day-1, intramuscularly) or their solvents. Lithium chloride (16.7 mg kg-1, i.p.) was given as a single dose on the fifth day; renal functions were then measured. 3. Indomethacin, in the absence of any effect on creatinine clearance, increased renal fractional lithium reabsorption and led to an increase in plasma lithium levels. 4. Losartan did not modify renal lithium handling and its plasma level. No change was observed in renal lithium clearance, the quantity of filtered lithium or the fractional reabsorption of the metal. As expected, losartan had no effect on systolic blood pressure in normotensive rats. 5. In conclusion, our results indicate that losartan, when given orally in the rat at a dose of 10 mg kg-1 day-1 over five days, does not modify renal lithium handling. They suggest that blockade of the angiotensin II receptors does not interfere with renal lithium reabsorption, which occurs mainly at a proximal tubular site.

Vascular kinin B(1) and B(2) receptor-mediated effects in the rat isolated perfused kidney - differential regulations.

1. Bradydykinin (BK) and analogs acting preferentially at kinin B(1) or B(2) receptors were tested on the rat isolated perfused kidney. Kidneys were perfused in an open circuit with Tyrode's solution. Kidneys preconstricted with prostaglandin F(2alpha) were used for the analysis of vasodilator responses. 2. BK induced a concentration-dependent renal relaxation (pD(2)=8.9+/-0.4); this vasodilator response was reproduced by a selective B(2) receptor agonist, Tyr(Me)(8)-BK (pD(2)=9.0+/-0.1) with a higher maximum effect (E(max)=78.9+/-6.6 and 55.8+/-4.3% of ACh-induced relaxation respectively, n=6 and 19, P<0.02). Icatibant (10 nM), a selective B(2) receptor antagonist, abolished BK-elicited relaxation. Tachyphylaxis of kinin B(2) receptors appeared when repeatedly stimulated at 10 min intervals. 3. Des-Arg(9)-BK, a selective B(1) receptor agonist, induced concentration-dependent vasoconstriction at micromolar concentration. Maximum response was enhanced in the presence of lisinopril (1 microM) and inhibited by R 715 (8 microM), a selective B(1) receptor antagonist. Des-Arg(9)-[Leu(8)]-BK behaved as an agonist. 4. A contractile response to des-Arg(9)-BK occurred after 1 of perfusion and increased with time by a factor of about three over a 3 h perfusion. This post-isolation sensitization to des-Arg(9)-BK was abolished by dexamethasone (DEX, 30 mg kg(-1) i.p., 3 h before the start of the experiment and 10 microM in perfusate) and actinomycin D (2 microM). Acute exposure to DEX (10 microM) had no effect on sensitized des-Arg(9)-BK response, in contrast to indomethacin (30 microM) that abolished it. DEX pretreatment however had no effect on BK-induced renal vasodilation. 5. Present results indicate that the main renal vascular response to BK consists of relaxation linked to the activation of kinin B(2) receptors which rapidly desensitize. Renal B(1) receptors are also present and are time-dependently sensitized during the in vitro perfusion of the rat kidneys.

Signal transduction pathways involved in kinin B(2) receptor-mediated vasodilation in the rat isolated perfused kidney.

The signal transduction pathways involved in kinin B(2) receptor-related vasodilation were investigated in rat isolated perfused kidneys. During prostaglandin F(2alpha) or KCl-induced constriction, the vasodilator response to a selective B(2) receptor agonist, Tyr(Me)(8)bradykinin (Tyr(Me)(8)BK), was assessed. Tyr(Me)(8)BK produced a concentration- and endothelium-dependent relaxation that was decreased by about 30 - 40% after inhibition of nitric oxide (NO) synthase by N(G)-nitro-L-arginine (L-NOARG) or of cyclo-oxygenase by indomethacin; a greater decrease (about 40 - 50%) was observed after concomitant inhibition of the two pathways. High extracellular K(+) diminished Tyr(Me)(8)BK-induced relaxation by about 75% suggesting a major contribution of endothelium-derived hyperpolarization. The residual response was almost completely suppressed by NO synthase and cyclo-oxygenase inhibition. The K(+) channel inhibitors, tetrabutylammonium (non-specific) and charybdotoxin (specific for Ca(2+)-activated K(+) channel), suppressed Tyr(Me)(8)BK-induced relaxation resistant to L-NOARG and indomethacin. Inhibition of cytochrome P450 (clotrimazole or 7-ethoxyresorufin) decreased the NO/prostanoids-independent relaxation to Tyr(Me)(8)BK by more than 60%, while inhibition of the cannabinoid CB(1) receptor (SR 141716A) had only a moderate effect. Acetylcholine induced a concentration-dependent relaxation with characteristics nearly similar to the response to Tyr(Me)(8)BK. In contrast, the relaxation elicited by sodium nitroprusside was potentiated in the absence of NO (L-NOARG or removal of endothelium) but remained unchanged otherwise. These results indicate that the activation of kinin B(2) receptors in the rat isolated kidney elicits an endothelium-dependent vasorelaxation, mainly dependent on the activation of charybdotoxin-sensitive Ca(2+)-activated K(+) channels. In addition, cytochrome P450 derivatives appear to be involved.

A potent new beta2-adrenoceptor blocking agent.

1 (t-Butyl-amino-3-ol-2-propyl) oximino-9 fluorene is a new beta2-adrenoceptor blocking agent with a pA2 of 9.23+/-0.25 on isolated trachea. 2 It provokes hypertension in normotensive rats and does not prevent arterial hypertension in SHR rats, although it does prevent the renin secretion normally induced by isoprenaline infusion.

Overnight decrease in hematocrit after nasal CPAP treatment in patients with OSA.

To clarify the paradox of a decrease in urine and sodium excretion occurring along with the elimination of peripheral edema when patients with obstructive sleep apnea (OSA) are treated with nasal continuous positive airway pressure (CPAP), we investigated the immediate effects of this treatment on the hematocrit and red blood cell count in eight patients with OSA. The hematocrit decreased in all patients, from a mean of 45.6 +/- 1.2 percent to 43.0 +/- 1.4 percent, with a parallel decrease in the red blood cell count from 4.777 +/- 0.168 millions/cu mm to 4.577 +/- 0.174 millions/cu mm (p less than 0.0005, one-tailed, in both cases). These results suggest that nasal CPAP treatment causes a hemodilution in patients with OSA, and are compatible with the hypothesis of an atrial natriuretic peptide-induced fluid shift from the intravascular to the extravascular volume in untreated patients with OSA. The reversal of these changes with CPAP treatment could explain the simultaneous decrease in sodium and urine excretion and the reduction of peripheral edema.

Pulmonary hemodynamics in patients with chronic obstructive pulmonary disease before and during an episode of peripheral edema.

We have investigated pulmonary hemodynamics in 16 patients with COPD with respiratory insufficiency, exhibiting marked peripheral edema. All the patients had previously undergone, within the last 6 months (T1), a right heart catheterization, in a stable state of their disease, when they were free of edema. Patients were subdivided into two groups according to the level of right ventricular end-diastolic pressure (RVEDP) during the episode of edema (T2): patients with a markedly elevated RVEDP (> 12 mm Hg) indicating the presence of right ventricular failure (RVF) = group 1, n = 9; patients with a normal or slightly elevated RVEDP (< 12 mm Hg) = group 2 (no RVF), n = 7. In group 1 pulmonary artery mean pressure (PAP) increased very significantly from T1 (27 +/- 5) to T2 (40 +/- 6 mm Hg, p < 0.001) as did RVEDP, from 7.5 +/- 3.9 to 13.4 +/- 1.2 mm Hg (p < 0.001). These hemodynamic changes paralleled a marked worsening of arterial blood gases, PaO2 falling from 63 +/- 4 to 49 +/- 7 mm Hg (p < 0.01) and PaCO2 increasing from 46 +/- 7 to 59 +/- 14 mm Hg (p < 0.01). On the other hand, in group 2, PAP was stable during the episode of edema (from 20 +/- 6 to 21 +/- 5 mm Hg), as was RVEDP (from 5.5 +/- 2.4 to 5.1 +/- 1.5 mm Hg), and changes in arterial blood gases from T1 to T2 were small and nonsignificant. It is concluded that RVF is effectively present in at least some patients with COPD with peripheral edema and is associated with a significant increase of PAP from baseline, probably accounted for by hypoxic vasoconstriction. Thus, pressure overload may contribute to the development of RVF. In other patients there are no hemodynamic signs of RVF, PAP is stable, and the origin of edema is not well understood.

L-dopa and streptozotocin-induced diabetic nephropathy in rats.

The purpose of the present study was to determine whether the physiological dopamine prodrug, L-dopa, could suppress streptozotocin-induced diabetic glomerular hyperfiltration, and thus prevent further evolution of the diabetic nephropathy. Male Wistar rats treated with streptozotocin (60 mg/kg, intravenously) rapidly developed hyperglycemia which was stabilized (congruent to 4 g/L) by a daily insulin injection. Within two weeks, a significant increase in glomerular filtration rate (GFR) and a rise in the filtration fraction were observed as described in the early stage of diabetic nephropathy. Increase in both GFR and in the filtration fraction were normalized by treating the rats with L-dopa (10 mg/kg, subcutaneously, twice a day for one week). The effects of L-dopa were linked to endorenal DA synthesis and to DA-1 receptor stimulation since both carbidopa and SCH 23390 suppressed them.

Renal dopamine synthesis from precursors.

In the Wistar rat in vivo L-dopa (10 mg/kg, subcutaneously) was shown to have the characteristics of a kidney-directed dopamine (DA) prodrug: two daily injections increased 24 h urinary DA excretion 450-fold but had no systemic effects on blood pressure and heart rate. In inactin-anesthesized rats, L-dopa increased natriuresis, diuresis and renal blood flow; these effects were linked to endorenal DA synthesis and to DA-1 receptor stimulation since they were suppressed by both carbidopa and SCH 23390. In the isolated perfused rat kidney, DA was synthesized from L-dopa with a greater yield than from gludopa. In nonfiltering kidneys, L-dopa metabolism was not limited when the access to dopa decarboxylase was restricted to the basolateral membrane. The same was not true for gludopa, for which the basolateral metabolism was low.

Effects of chlorpromazine and lorazepam on explicit memory, repetition priming and cognitive skill learning in healthy volunteers.

To assess the influence of neuroleptics on explicit memory and two forms of implicit memory, repetition priming and cognitive skill learning, the effects of two low doses of chlorpromazine (12.5 and 25 mg orally) were contrasted to those of lorazepam (2.5 mg orally) and of a placebo using a free-recall task, a word-completion task and repeated testing on the Tower of Toronto puzzle, a version of the Tower of Hanoi puzzle. Seventy-two healthy volunteers took part in this double-blind study. Chlorpromazine spared free-recall and word-completion performance, but impaired the acquisition of a cognitive routine in the subjects who completed the first trials of the Tower of Toronto puzzle efficiently. Lorazepam induced an opposite pattern of memory disruption. These preliminary results suggest that chlorpromazine and lorazepam induced a double dissociation between priming and the acquisition of a cognitive routine. They provide evidence that the two forms of implicit memory rely upon distinct neurochemical systems, the latter, but not the former, being dependent upon dopaminergic systems.

Differential effects of diazepam and lorazepam on repetition priming in healthy volunteers.

The effects of two benzodiazepines, diazepam (15 or 20 mg orally) and lorazepam (1.75 or 2.5 mg orally), and a placebo on explicit memory, lexical priming and perceptual priming were assessed using a free-recall, a word-completion and a picture-completion test. The picture-completion test included two different study conditions intended to manipulate the magnitude of the priming effect. Sixty healthy volunteers took part in this double-blind study. Free-recall performances were altered by both drugs. Lorazepam impaired word-completion and picture-completion performance, whereas diazepam only exhibited a deleterious effect on the more sensitive of the two measures of the picture-completion test. These results indicate that the two benzodiazepines have differential amnestic effects. It is suggested that these differential effects could be accounted for by a different cortical distribution of the two benzodiazepines.

Time course of the effects of diazepam and lorazepam on perceptual priming and explicit memory.

The effects of diazepam and lorazepam on explicit memory and perceptual priming were studied 50, 130 and 300 min after drug administration. Sixty healthy volunteers were randomly assigned to one of five parallel groups (placebo, diazepam 0.2 or 0.3 mg/kg, lorazepam 0.026 or 0.038 mg/kg). The corresponding doses of benzodiazepines exerted a similar negative effect on explicit performance. Lorazepam markedly impaired priming performance, whereas the effect of diazepam was intermediate between that of placebo and that of lorazepam 0.038 mg/kg. The impairment was maximal at the theoretical peak plasma concentration. Contamination by explicit memory could account for the decrease in priming performance observed in the diazepam groups.