Acute overdosage of up to 20g has been reported several times with no significant ill-effects. Induction of vomiting and/or gastric lavage may be employed together with symptomatic and supportive therapy.
Acute overdosage of up to 20 grams has been reported several times with no significant ill effects. Induction of vomiting and/or gastric lavage may be employed together with symptomatic and supportive therapy.
Acute overdosage of up to 20g has been reported several times with no significant ill effects. Induction of vomiting and/or gastric lavage may be employed together with symptomatic and supportive therapy.
Not applicable.
Adverse experiences with cimetidine are listed below by system organ class and frequency. Frequencies are defined as: very common (>1/10), common (>1/100, <1/10), uncommon (>1/1000, <1/100), rare (>1/10000, <1/1000), very rare (<1/10000).
Blood and lymphatic system disorders
Uncommon: Leukopenia
Rare: Thrombocytopenia, aplastic anaemia
Very rare: Pancytopenia, agranulocytosis
Immune system disorders
Very rare: Anaphylaxis. Anaphylaxis is usually cleared on withdrawal of the drug.
Psychiatric disorders
Uncommon: Depression, confusional states, hallucinations. Confusional states, reversible within a few days of withdrawing cimetidine, have been reported, usually in elderly or ill patients.
Nervous system disorders
Common: Headache, dizziness
Cardiac disorders
Uncommon: Tachycardia
Rare: Sinus bradycardia
Very rare: Heart block
Gastrointestinal disorders
Common: Diarrhoea
Very rare: Pancreatitis. Pancreatitis cleared on withdrawal of the drug.
Hepatobiliary disorders
Uncommon: Hepatitis
Rare: Increased serum transaminase levels. Hepatitis and increased serum transaminase levels cleared on withdrawal of the drug.
Skin and subcutaneous tissue disorders
Common: Skin rashes
Very rare: Reversible alopecia and hypersensitivity vasculitis. Hypersensitivity vasculitis usually cleared on withdrawal of the drug.
Musculoskeletal and connective tissue disorders
Common: Myalgia
Very rare: Arthralgia
Renal and urinary disorders
Uncommon: Increases in plasma creatinine
Rare: Interstitial nephritis. Interstitial nephritis cleared on withdrawal of the drug. Small increases in plasma creatinine have been reported, unassociated with changes in glomerular filtration rate. The increases do not progress with continued therapy and disappear at the end of therapy.
Reproductive system and breast disorders
Uncommon: Gynaecomastia and reversible impotence. Gynaecomastia is usually reversible upon discontinuation of cimetidine therapy. Reversible impotence has been reported particularly in patients receiving high doses (e.g. in Zollinger-Ellison Syndrome). However, at regular dosage, the incidence is similar to that in the general population.
Very rare: Galactorrhoea
General disorders and administration site conditions
Common: Tiredness
Very rare: Fever. Fever cleared on withdrawal of the drug.
Reporting of suspected adverse reactions
Reporting suspected adverse reactions after authorisation of the medicinal product is important. It allows continued monitoring of the benefit/risk balance of the medicinal product. Healthcare professionals are asked to report any suspected adverse reactions via the Yellow Card Scheme at: www.mhra.gov.uk/yellowcard.
Adverse experiences with Zitac are listed below by system organ class and frequency. Frequencies are defined as: very common (>1/10), common (>1/100, <1/10), uncommon (>1/1000, <1/100), rare (>1/10000, <1/1000), very rare (<1/10000).
Blood and Lymphatic system disorders:
Uncommon: Leukopenia
Rare: Thrombocytopenia, aplastic anaemia
Very rare: Pancytopenia, agranulocytosis
Immune system disorders:
Very rare: Anaphylaxis. Anaphylaxis is usually cleared on withdrawal of the drug.
Psychiatric disorders
Uncommon: Depression, confusional states, hallucinations. Confusional states, reversible within a few days of withdrawing Zitac, have been reported, usually in elderly or ill patients.
Nervous system disorders
Common: Headache, dizziness
Cardiac disorders
Uncommon: Tachycardia
Rare: Sinus bradycardia
Very rare: Heart block
Gastrointestinal disorders
Common: Diarrhoea
Very rare: Pancreatitis. Pancreatitis cleared on withdrawal of the drug.
Hepatobiliary disorders
Uncommon: Hepatitis
Rare: Increased serum transaminase levels. Hepatitis and increased serum transaminase levels cleared on withdrawal of the drug.
Skin and subcutaneous tissue disorders
Common: Skin rashes
Very rare: Reversible alopecia and hypersensitivity vasculitis. Hypersensitivity vasculitis usually cleared on withdrawal of the drug.
Musculoskeletal and connective tissue disorders
Common: Myalgia
Very rare: Arthralgia
Renal and urinary disorders
Uncommon: Increases in plasma creatinine
Rare: Interstitial nephritis. Interstitial nephritis cleared on withdrawal of the drug. Small increases in plasma creatinine have been reported, unassociated with changes in glomerular filtration rate. The increases do not progress with continued therapy and disappear at the end of therapy.
Reproductive system and breast disorders
Uncommon: Gynaecomastia and reversible impotence. Gynaecomastia is usually reversible upon discontinuation of Zitac therapy. Reversible impotence has been reported particularly in patients receiving high doses (e.g. in Zollinger-Ellison Syndrome). However, at regular dosage, the incidence is similar to that in the general population.
Very rare: Galactorrhoea
General disorders and administration site conditions
Common: Tiredness
Very rare: Fever. Fever cleared on withdrawal of the drug.
Reporting of suspected adverse reactions
Reporting suspected adverse reactions after authorisation of the medicinal product is important. It allows continued monitoring of the benefit/risk balance of the medicinal product. Healthcare professionals are asked to report any suspected adverse reactions via the Yellow Card Scheme at: www.mhra.gov.uk/yellowcard.
Over 56 million patients have been treated with cimetidine world-wide and adverse reactions have been infrequent.
Blood and the lymphatic system disorders
Thrombocytopenia and leucopenia, including agranulocytosis (see Special warnings and precautions for use), reversible on withdrawal of treatment, have been reported rarely; pancytopenia and aplastic anaemia have been reported very rarely.
Immune
In common with other H2-receptor antagonists, there have been very rare reports of anaphylaxis. Rare cases of hypersensitivity vasculitis have been reported. These usually clear on withdrawal of the drug.
Endocrine Disorders
Gynaecomastia has been reported and is always reversible on discontinuing treatment. There have been rare reports of acute pancreatitis which is reversible on withdrawal of treatment.
Psychiatric Disorders
Reversible confusional states have occurred, usually in elderly or already very ill patients, e.g. those with renal failure.
Hallucination has been reported rarely.
Depression has been reported infrequently.
Cardiac
There are rare reports of sinus bradycardia, tachycardia and heart block which are all reversible on withdrawal of treatment.
Hepato-biliary disorders
Biochemical or biopsy evidence of reversible liver damage has been reported occasionally as have rare cases of hepatitis.
Musculoskeletal, connective tissue and bone disorders
There have been rare reports of myalgia and arthralgia which is reversible on withdrawal of treatment.
Renal and Urinary Disorders
Isolated increases of plasma creatinine have been of no clinical significance.
There have been very rare reports of interstitial nephritis which is reversible on withdrawal.
Reproductive system and breast disorders
Reversible impotence has also been very rarely reported but no causal relationship has been established at usual therapeutic doses.
General Disorders
Diarrhoea, dizziness or rash, usually mild or transient, and tiredness have been reported.
There are rare reports of fever and headache which are reversible on withdrawal of treatment.
Alopecia has been reported but no causal relationship has been established.
Not available.
There are no preclinical data of relevance to the prescriber which are additional to that already included in other sections of the SPC.
Relevant information for the prescriber is provided elsewhere in the Summary of Product Characteristics.
Cimetidine, one of the H2 blockers is a reversible, competitive antagonist of the actions of histamine on H2 receptors. It is highly selective in its action and is virtually without effect on H1 receptors or, indeed on receptors for other autacoids or drugs. The most prominent of the effects of histamine that are mediated by H2 receptors is stimulation of gastric acid secretion and they interfere remarkably little with physiological functions other than gastric secretion.
Cimetidine inhibits gastric acid secretion elicited by histamine or other H2 agonists in a dose-dependent, competitive manner; the degree of inhibition parallels the plasma concentration of the drug over a wide range. In addition, the H2 blockers inhibit gastric secretion elicited by muscarinic agonists or by gastrin, although this effect is not always complete.
This breadth of inhibitory effect is not due to non-specific actions at the receptors for these other secretagogues. Rather, this effect, which is non-competitive and indirect, appears to indicate either that these two classes of secretagogues utilise histamine as the final common mediator or, more probably, that ongoing histaminergic stimulation of the parietal cell is important for amplification of the stimuli provided by ACh or gastrin when they act on their own discrete receptors. Receptors for all three secretagogues are present on the parietal cell. The ability of H2 blockers to suppress responses to all three physiological secretagogues makes them potent inhibitors of all phases of gastric acid secretion. Thus these drugs will inhibit basal (fasting) secretion and nocturnal secretion and also that stimulated by food, sham feeding, fundic distension, insulin, or caffeine. The H2 blockers reduce both the volume of gastric juice secreted and its hydrogen ion concentration. Output of pepsin, which is secreted by the chief cells of the gastric glands (mainly under cholinergic control), generally falls in parallel with the reduction in volume of the gastric juice. Secretion of intrinsic factor is also reduced, but it is normally secreted in great excess, and absorption of vitamin B12 is usually adequate even during long-term therapy with H2 blockers.
Concentrations of gastrin in plasma are not significantly altered under fasting conditions; however, the normal prandial elevation of gastrin concentration may be augmented, apparently as a consequence of a reduction in the negative feedback that is normally provided by acid.
Pharmacotherapeutic Group: H2-receptor Antagonists, ATC code: A02BA01
Zitac is a histamine H2-receptor antagonist which rapidly inhibits both basal and stimulated gastric secretion of acid and reduces pepsin output. It is a reversible, competitive antagonist, and is used as an anti-ulcer drug. It is highly selective in its action, is virtually without effect on H1 receptors, or indeed on receptors for other autocoids or drugs. Despite the widespread distribution of H2-receptors in the body, Zitac interferes remarkably little with physiological functions other than gastric secretion, implying that the extragastric H2-receptors are of minor physiological importance.
However, H2 blockers like Zitac do inhibit those effects on the cardiovascular and other systems that are elicited through the corresponding receptors by exogenous or endogenous histamine.
Zitac inhibits gastric acid secretion elicited by histamine or other H2 agonists in a dose-dependent, competitive manner; the degree of inhibition parallels the plasma concentration of the drug over a wide range. In addition, the H2 blockers inhibit gastric secretion elicited by muscarinic agonists or by gastrin, although this effect is not always complete.
This breadth of inhibitory effect is not due to non-specific actions at the receptors for these other secretagogues. Rather, this effect, which is non-competitive and indirect, appears to indicate either that these two classes of secretagogues utilise histamine as the final common mediator or, more probably, that ongoing histaminergic stimulation of the parietal cell is important for amplification of the stimuli provided by ACh or gastrin when they act on their own discrete receptors. Receptors for all three secretagogues are present on the parietal cell. The ability of H2 blockers to suppress responses to all three physiological secretagogues makes them potent inhibitors of all phases of gastric acid secretion. Thus these drugs will inhibit basal (fasting) secretion and nocturnal secretion and also that stimulated by food, sham feeding, fundic distension, insulin, or caffeine. The H2 blockers reduce both the volume of gastric juice secreted and its hydrogen ion concentration. Output of pepsin, which is secreted by the chief cells of the gastric glands (mainly under cholinergic control), generally falls in parallel with the reduction in volume of the gastric juice. Secretion of intrinsic factor is also reduced, but it is normally secreted in great excess, and absorption of vitamin B12 is usually adequate even during long-term therapy with H2 blockers.
Concentrations of gastrin in plasma are not significantly altered under fasting conditions; however, the normal prandial elevation of gastrin concentration may be augmented, apparently as a consequence of a reduction in the negative feedback that is normally provided by acid.
Cimetidine is a histamine H2-receptor antagonist; it is highly selective in its action and is virtually without effect on H1 receptors or, indeed on receptors for other autacoids or drugs. The most prominent of the effects of histamine that are mediated by H2 receptors is stimulation of gastric acid secretion and they interfere remarkably little with physiological functions other than gastric secretion.
Cimetidine inhibits gastric acid secretion elicited by histamine or other H2 agonists in a dose-dependent, competitive manner; the degree of inhibition parallels the plasma concentration of the drug over a wide range. In addition, the H2 blockers inhibit gastric secretion elicited by muscarinic agonists or by gastrin, although this effect is not always complete.
This breadth of inhibitory effect is not due to the non-specific actions at the receptors for these other secretagogues. Rather, this effect, which is non-competitive and indirect, appears to indicate either that these two classes of secretagogues utilise histamine as the final common mediator or, more probably, that ongoing histaminergic stimulation of the parietal cell is important for amplification of the stimuli provided by ACh or gastrin when they act on their own discrete receptors. Receptors for all three secretagogues are present on the parietal cell. The ability of H2 blockers to suppress responses to all three physiological secretagogues makes them potent inhibitors of all phases of gastric acid secretion. Thus these drugs will inhibit basal (fasting) secretion and nocturnal secretion and also that stimulated by food, sham feeding, fundic distension, insulin or caffeine. The H2 blockers reduce both the volume of gastric juice secreted and its hydrogen ion concentration. Output of pepsin, which is secreted by the chief cells of the gastric glands (mainly under cholinergic control), generally falls in parallel with the reduction in volume of the gastric juice. Secretion of intrinsic factor is also reduced, but it is normally secreted in great excess, and absorption of vitamin B12 is usually adequate even during long-term therapy with H2 blockers.
Concentrations of gastrin in plasma are not significantly altered under fasting conditions; however, the normal prandial elevation of gastric concentration may be augmented, apparently as a consequence of a reduction in the negative feedback that is normally provided by acid
Cimetidine is rapidly and virtually completely absorbed. Absorption is little impaired by food or by antacids. Peak concentrations in plasma are attained in about 1 to 2 hours. Hepatic first-pass metabolism results in bioavailabilities of about 60% for cimetidine. The elimination half-life is about 2 to 3 hours. Cimetidine is eliminated primarily by the kidneys, and 60% or more may appear in the urine unchanged; much of the rest is oxidation products. Small amounts are recovered in the stool.
Zitac is rapidly and virtually completely absorbed from the gastro-intestinal tract. Absorption is little impaired by food or by antacids. Peak plasma concentrations are obtained about an hour after administration on an empty stomach, and about 2 hours after administration with food. The duration of action is reported to be prolonged by administration with food. Peak concentrations in plasma are attained in about 1 to 2 hours. Hepatic first-pass metabolism results in bioavailabilities of about 60% for Zitac. The elimination half-life is about 2-3 hours. Zitac is eliminated primarily by the kidneys, and 60% or more may appear in the urine unchanged; much of the rest is oxidation products. Small amounts are recovered in the stools.
Zitac crosses the placental barrier and is excreted in milk. It does not readily cross the blood-brain barrier.
Cimetidine is rapidly and virtually completely absorbed. Absorption is little impaired by food or by antacids. Peak concentrations in plasma are attained in about 1 to 2 hours. Hepatic first-pass metabolism results in bioavailabilities of about 60% for cimetidine. The elimination half -life is about 2 -3 hours. The effects on acid secretion are of longer duration. Cimetidine is eliminated primarily by the kidneys, and 60% or more may appear in the urine unchanged; much of the rest is oxidation products. Small amounts are recovered in the stool.
None known.
None known
Not applicable.
Not applicable.
Nothing stated.
Not applicable
Administrative data
