Ranitidine headache

Transition of Products From Prescription to Over the Counter: The H2 Antagonists

In general, the histamine type-2 receptor antagonists (H2RA) enjoy an enviable record of safety. These agents, notably cimetidine, have been studied extensively in clinical trials, case reports, and worldwide drug use reporting systems. Of the available agents (cimetidine, famotidine, nizatidine, and ranitidine) several similarities exist from compound to compound and use data to support that each of the agents is equally safe and efficacious in equipotent dosing. A review of H2RA pharmacology, pharmacokinetics, adverse effects, and drug interactions is included to provide the clinician with a basis for rational selection and use of an H2RA.

The effect of cimetidine and ranitidine on cognitive function in postoperative cardiac surgical patients

OBJECTIVE

To compare the incidence of delirium in postoperative cardiac surgical patients treated with either cimetidine or ranitidine.

METHOD

Cardiac surgery patients were randomized to receive either cimetidine or ranitidine postoperatively. Each patient underwent three Mini-Mental Status Examinations (MMSE) and the medical record was reviewed for pertinent past medical history, laboratory data, and evidence of delirium on three occasions: one day preoperatively (before H-2 blocker was given), in the early postoperative period (while receiving the H-2 blocker); usually two days postoperatively on the day of hospital discharge (several days after the H2 blocker had been discontinued).

RESULTS

Overall, both groups in the early postoperative period showed a significant decrease in the MMSE score (27.11 +/- 4.44 to 25.38 +/-2.87, mean +/- SD; t = 5.16, p < .0005), which resolved by the time of hospital discharge. There was no significant difference between cimetidine and ranitidine. Both age and preoperative MMSE score were strongly associated with the development of delirium.

CONCLUSIONS

We found no significant difference between cimetidine's versus ranitidine's effect upon cognitive functioning in the postoperative cardiac surgical patient. This was true even when controlling for age and length of stay.

Treatment considerations in headache and associated medical disorders

As more headache sufferers seek medical care for their headaches, it is incumbent on physicians to consider all of a patient's medical illnesses in choosing therapy. The availability of new medications for headache will facilitate the tailoring of treatment to specific patient needs. The physician who treats patients with headache and concomitant medical problems must be knowledgeable about the pharmacology and adverse effects of these agents. This will permit the practitioner to use specific therapy, limit the number of medications prescribed, and prevent an exacerbation of either the medical condition or the headaches.

Concomitant medical disease and headache

The treatment of headache disorders in patients with concomitant medical illness constitutes one of the more challenging areas of headache therapy. As new agents are added to our pharmacologic armamentarium, it will become easier to tailor therapy to our patients. The physician who treats the headache patient with concomitant medical illness must be particularly aware of drug side effects and pharmacology in order to prevent a worsening of underlying medical conditions or an exacerbation of headaches.

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)

Ranitidine. An updated review of its pharmacodynamic and pharmacokinetic properties and therapeutic use in peptic ulcer disease and other allied diseases

Ranitidine, a histamine H2-receptor antagonist, is now well established as a potent inhibitor of gastric acid secretion effective in the treatment and prophylaxis of gastrointestinal lesions aggravated by gastric acid secretion. Therapeutic trials involving several thousands of patients with peptic ulcer disease confirm that ranitidine 300mg daily administered orally in single or divided doses is at least as effective as cimetidine 800 to 1000mg daily in increasing the rate of healing of duodenal and gastric ulcers. Similar dosages of ranitidine have been shown to relieve the symptoms of reflux oesophagitis and heal or prevent gastrointestinal damage caused by ulcerogenic drugs. Ranitidine 150mg orally at night maintains ulcer healing in the long term. Ranitidine has also demonstrated good results in the treatment of Zollinger-Ellison syndrome and in the prevention of aspiration pneumonitis when given prior to surgery and to pregnant women at full term. It may also have a place in the management of acute upper gastrointestinal bleeding and in the prevention of stress ulcers in the intensive care setting, although these areas require further investigation. Ranitidine has been used safely in obstetric patients during labour, in children, the elderly, and in patients with renal impairment when given in appropriate dosages. The drug is very well tolerated and is only infrequently associated with serious adverse reactions or clinically significant drug interactions. Even at high dosages, ranitidine appears devoid of antiandrogenic effects. Ranitidine is clearly comparable or superior to most other antiulcer agents in the treatment and prevention of a variety of gastrointestinal disorders associated with gastric acid secretion. With its favourable efficacy and tolerability profiles, ranitidine must be considered a first-line agent when suppression of gastric acid secretion is indicated.

Pharmacodynamics and pharmacokinetics of parenteral histamine (H2)-receptor antagonists

Parenteral histamine (H2)-receptor antagonists are frequently used to prevent upper gastrointestinal bleeding caused by stress-induced gastric mucosal damage in critically ill patients. It is generally agreed that the goal of therapy in this syndrome is the consistent elevation of gastric pH levels above a certain value, often set at 4, in order to prevent the underlying mucosal damage from progressing to bleeding. The three H2-receptor antagonists currently available in a parenteral form and suitable for this mode of prophylaxis are cimetidine, ranitidine, and famotidine. The pharmacodynamic and pharmacokinetic properties of these agents, as they relate to their use in prevention of stress ulceration bleeding, are discussed here. These agents are more noted for their pharmacodynamic and pharmacokinetic similarities in acid suppression, elimination, and metabolism than for their differences. Ranitidine and famotidine are more potent than cimetidine, and famotidine has a slightly longer half-life than do cimetidine and ranitidine, but current dosing recommendations take these differences into account so that the agents have equivalent efficacy. Cimetidine and ranitidine have been widely used in this application. Less experience has been obtained, to date, with famotidine. Recent studies with primed, continuous infusions of cimetidine indicate that dosing schedule may be the key to obtaining better efficacy in prophylaxis of stress-related mucosal damage. Similar studies with ranitidine have not yielded results as promising as those with cimetidine, however, and few data are available on famotidine.

Safety perspectives on parenteral H2-receptor antagonists

Much controversy has been associated with the similarities and differences among the histamine (H2)-receptor antagonists with respect to safety. The safety issues, including those recently identified with the use of parenteral H2-receptor antagonists, are analyzed here with the intent of placing these data into proper perspective. The focus of the analysis is on a few of the more important issues: central nervous system effects and clinically significant drug interactions. A review of the voluminous safety literature on these agents indicates that, as a class, they have enviable safety records. When individual agents are compared, some small differences in safety profiles emerge, but, on the whole, similarities are more striking.

Clinically important adverse effects and drug interactions with H2-receptor antagonists: an update

The H2-receptor antagonists cimetidine, ranitidine, and famotidine are well tolerated, with a low frequency and similar spectrum of adverse effects. The occasional problematic effects that have been associated with these agents include central nervous system symptoms (mental confusion, headache, and depression), rare cases of thrombocytopenia, and cardiovascular events related to the rate of intravenous infusion. Severe renal and hepatic impairment appear to be associated with a higher occurrence of central nervous system effects. Because the H2-receptor antagonists elevate gastric pH, bind to and inhibit the hepatic cytochrome P-450 enzyme system, and undergo renal tubular secretion, competition with other drugs sharing these pathways has resulted in a number of drug interactions, most of which are not clinically significant. The interaction that occurs with theophylline and warfarin when the cytochrome P-450 enzyme system is inhibited by cimetidine and ranitidine requires monitoring. Recent data suggest that administering cimetidine 800 mg at bedtime has less effect on the serum concentrations of warfarin and theophylline than other dosing regimens. Evidence to date indicates that famotidine does not bind to cytochrome P-450 to a significant extent, and interactions with drugs metabolized by this system have not been reported; however, clinical experience with this agent is very limited.