Effect of pretreatment with ranitidine on the hypnotic action of single doses of midazolam, temazepam and zopiclone. A clinical study

Clinically important drug interactions with zopiclone, zolpidem and zaleplon

Insomnia, an inability to initiate or maintain sleep, affects approximately one-third of the American population. Conventional benzodiazepines, such as triazolam and midazolam, were the treatment of choice for short-term insomnia for many years but are associated with adverse effects such as rebound insomnia, withdrawal and dependency. The newer hypnosedatives include zolpidem, zaleplon and zopiclone. These agents may be preferred over conventional benzodiazepines to treat short-term insomnia because they may be less likely to cause significant rebound insomnia or tolerance and are as efficacious as the conventional benzodiazepines. This review aims to summarise the published clinical drug interaction studies involving zolpidem, zaleplon and zopiclone. The pharmacokinetic and pharmacodynamic interactions that may be clinically important are highlighted. Clinical trials have studied potential interactions of zaleplon, zolpidem and zopiclone with the following types of drugs: cytochrome P450 (CYP) inducers (rifampicin), CYP inhibitors (azoles, ritonavir and erythromycin), histamine H(2) receptor antagonists (cimetidine and ranitidine), antidepressants, antipsychotics, antagonists of benzodiazepines and drugs causing sedation. Rifampicin significantly induced the metabolism of the newer hypnosedatives and decreased their sedative effects, indicating that a dose increase of these agents may be necessary when they are administered with rifampicin. Ketoconazole, erythromycin and cimetidine inhibited the metabolism of the newer hypnosedatives and enhanced their sedative effects, suggesting that a dose reduction may be required. Addition of ethanol to treatment with the newer hypnosedatives resulted in additive sedative effects without altering the pharmacokinetic parameters of the drugs. Compared with some of the conventional benzodiazepines, fewer clinically important interactions appear to have been reported in the literature with zaleplon, zolpidem and zopiclone. The fact that these drugs are newer to the market and have not been as extensively studied as the conventional benzodiazepines may be the reason for this. Another explanation may be a difference in CYP metabolism. While triazolam and midazolam are biotransformed almost entirely via CYP3A4, the newer hypnosedatives are biotransformed by several CYP isozymes in addition to CYP3A4, resulting in CYP3A4 inhibitors and inducers having a lesser effect on their biotransformation.

Side effects of ranitidine

Ranitidine was first marketed in 1981; since then many patients have been treated such that much experience has been accumulated on the safety of this histamine H2-receptor antagonist in the treatment of gastroduodenal disease. A wide array of ranitidine-associated side effects has been described, but infrequently. As so much information is now available, the aim of this review is to assess the weight of evidence for a causal link between ranitidine and the reported side effects. Overall, ranitidine is well tolerated. The incidence of general side effects at less than 2% is very similar to placebo. Headaches, tiredness, dizziness and mild gastrointestinal disturbance (e.g. diarrhoea, constipation and nausea) are among the most frequent complaints, but have very seldom resulted in stopping treatment. Cardiovascular side effects are extremely rare and unpredictable with the usual doses of oral ranitidine (at most 1 in 1 million patients). They mostly comprise sinusal bradycardia and atrioventricular blockade, especially after rapid intravenous administration, receding after cessation of the drug. Clinical studies, however, have not shown a significant pharmacological effect of ranitidine on the cardiovascular system via H2-receptors, even though individual sensitivities cannot be ruled out in a few isolated reports. Ranitidine is unlikely to be directly hepatotoxic: a transient change in liver function tests has been noted in only 1 in 100 to 1 in 1000 patients. Several cases of mixed hepatitis have been reported, but very few were fully documented. The incidence of ranitidine-associated acute hepatitis has been estimated to be less than 1 in 100,000 patients. Neuropsychiatric complications may be less common and clinically quite similar to those reported with cimetidine, i.e. confusion, disorientation, hallucinations, delirium. These side effects have occurred especially in critically ill and multiple-therapy patients, or patients with chronic renal or hepatic failure, so that the direct causal link with ranitidine treatment was often difficult to ascertain. Even though an H2-receptor-mediated effect is an attractive hypothesis (since similar complications were noted with other H2-receptor antagonists), other mechanisms have been suggested to play a role, e.g. cholinergic or histaminic effects. The overall incidence of neuropsychiatric complications is probably markedly less than 1%. White cell injury (i.e. agranulocytosis) appears to be the most frequent haematological complication, even though case reports are very few and poorly documented.(ABSTRACT TRUNCATED AT 400 WORDS)

Premedication for upper gastrointestinal endoscopy

Premedication is not essential to endoscopy but patient tolerance is clearly improved and, thus, ease of examination. Although comparable results can be achieved through nonpharmacologic means, the time and effort involved precludes their widespread use. Despite near universal utilization of premedication in endoscopy, the associated risk is difficult to determine from the available literature. The reported data reveal nominal risk yet must be viewed as minimums. The ideal drug with predictable clinical effects, minimal postprocedure impairment, little respiratory compromise, and proven antagonist is not yet available. Although midazolam seems to represent an advance, recent emphasis on respiratory depression is particularly troublesome. Studies evaluating various agents have suffered from lack of quantitation of such parameters as patient tolerance, ease of examination, and postprocedure impairment. Development of proven standards for these parameters would have to occur before a definitive double-blind randomized trial could be undertaken. Suggested means of assessing these parameters are listed in Table I. Improvement in major morbidity would be difficult in light of its low incidence. As the search for the ideal drug continues, endoscopists must continue to use drugs whose full effects are incompletely understood. The ability to increase patient comfort must be balanced with the small, but ever present, risk of morbidity and mortality.