Effect of renal or hepatic dysfunction on neurotoxic convulsion induced by ranitidine in mice

Prophylactic phenytoin does not improve cerebral edema or survival in acute liver failure--a controlled clinical trial

BACKGROUND/AIMS

Seizure activity in patients with acute liver failure (ALF) may increase cerebral oxygen requirements and worsen cerebral edema. Recently, prophylactic phenytoin has been recommended to suppress sub-clinical seizure activity evident on electroencephalographic monitoring. To determine the clinical utility of prophylactic phenytoin therapy in patients with ALF.

METHODS

Forty two patients with ALF were randomized. Twenty two patients were given prophylactic phenytoin and 22 patients acted as controls. The baseline clinical and biochemical features were similar in the two groups and patients with > or =2 poor prognostic variables were equally represented.

RESULTS

Sixteen patients in the phenytoin group, and 15 in the control group developed cerebral edema (P=0.38). Mechanical ventilation was required in 10 and 12 patients in the phenytoin and control groups, respectively, (P=0.77). Seizures occurred in 5 (22.7%) control patients and 5 (25%) phenytoin treated patients (P=0.86). Fourteen (70%) patients randomized to phenytoin and 15 (68.2%) control patients died (P=0.89).

CONCLUSIONS

Seizure was common in patients with ALF. Prophylactic use of phenytoin did not prevent cerebral edema, seizures or need for mechanical ventilation, and did not improve survival.

The effect of cimetidine on the pharmacodynamics of theophylline-induced seizures and ethanol hypnotic activity

Due to its availability as an over-the-counter drug, the use of cimetidine is increasing, thus adverse interactions with other commonly used agents may also increase. The aim of this study was to investigate whether acute administration of cimetidine could alter the pharmacodynamics of theophylline neurotoxicity and the hypnotic action of ethanol. To examine these questions, rats received a dose of 77 mg/kg cimetidine followed by a constant infusion of either theophylline (1.2 mg/min.) or ethanol (16.3 mg/min.) until the onset of the pharmacological end point, maximal seizure or loss of righting reflex, where samples of blood and brain were obtained and assayed for either theophylline or ethanol. We report that cimetidine in doses that may cause pharmacokinetic interactions did not affect the concentration-effect relationship of either the stimulating action of theophylline or the depressant activity of ethanol. These outcomes emphasize the relative safety which patients using cimetidine in self-medication rely on.

Distribution of ciprofloxacin into the central nervous system in rats with acute renal or hepatic failure

Pharmacokinetic changes of various drugs have been reported in renal or hepatic failure. The present study employed ciprofloxacin, a quinolone antibiotic having neurotoxic side effects, to assess the influence of these diseases on distribution of ciprofloxacin into the central nervous system (CNS). After intravenous dosing of ciprofloxacin (10-30 mg kg(-1)), ciprofloxacin levels in plasma and brain were measured in normal rats (Wistar, male, 10-week-old) and those with acute renal and hepatic injuries which were induced by uranyl nitrate and carbon tetrachloride (CCl4), respectively. In the uranyl nitrate-treated rats, the plasma elimination half-life of ciprofloxacin was prolonged and the total body clearance was reduced when compared with those in the normal rats. Similar but smaller changes were observed in the CCl4-treated group. Brain levels of ciprofloxacin were significantly increased by both uranyl nitrate and CCl4 treatments. A proportional correlation between serum unbound levels and brain levels of ciprofloxacin was observed in the normal group. However, brain-to-serum unbound concentration ratios of ciprofloxacin were reduced in the rats with renal or hepatic failure. These results suggest that renal failure as well as hepatic failure retards elimination of ciprofloxacin from the blood, leading to elevation of the CNS level, and also that ciprofloxacin distribution in the brain is reduced in these disease states.

Effect of acute renal failure on neurotoxicity of cimetidine in rats

PURPOSE

We investigated the effect of acute renal failure on the neurotoxicity of cimetidine in rats.

METHODS

Experimental acute renal failure was produced by bilateral ureteral ligation. Cimetidine was intravenously infused to ureter ligated (UL) and control rats, and cimetidine concentration in plasma, brain and cerebrospinal fluid (CSF) were compared.

RESULTS

The cimetidine concentration in plasma was rapidly increased in UL rats as compared to control rats. The cimetidine concentration in CSF at the onset of convulsion did not depend on the infusion rate, suggesting that cimetidine in CSF equilibrates rapidly with the site of action for clonic convulsion. The cimetidine concentration in CSF of UL rats at the onset of clonic convulsion was lower than those of control rats.

CONCLUSIONS

Increased sensitivity to the drug on the central nervous system may contribute to increased toxicity of cimetidine with renal failure.