Cimetidine 300mg Tablets
It is used to treat or prevent GI (gastrointestinal) ulcers.It is used to treat gastroesophageal reflux disease (GERD; acid reflux). It is used to treat heartburn and sour stomach.It is used to treat syndromes caused by lots of stomach acid.It may be given to you for other reasons. Talk with the doctor.
Drug Class
Histamine H2-receptor antagonist
Pharmacologic Class
H2-receptor antagonist
Pregnancy Category
Category B
FDA Approved
Aug 1977
DEA Schedule
Not Controlled
Overview
What is this medicine?
Cimetidine is a medication that helps reduce the amount of acid your stomach makes. It's used to treat and prevent ulcers, heartburn, and other conditions caused by too much stomach acid.
How to Use This Medicine
Taking Your Medication Correctly
To get the most benefit from your medication, take it exactly as directed by your doctor. Carefully read all the information provided with your prescription, and follow the instructions closely. Take your medication with meals and at bedtime, or as instructed by your doctor.
It's essential to avoid taking antacids at the same time as your medication. If you have any questions or concerns, discuss them with your doctor. To help prevent heartburn, take your medication 30 minutes before consuming foods or drinks that trigger heartburn.
Storing and Disposing of Your Medication
Store your medication at room temperature in a dry place, avoiding the bathroom. Keep all medications in a safe location, out of the reach of children and pets. Dispose of unused or expired medications properly. Do not flush them down the toilet or pour them down the drain unless instructed to do so by your doctor or pharmacist. If you're unsure about the best way to dispose of your medication, consult with your pharmacist. You may also want to check if there are drug take-back programs available in your area.
What to Do If You Miss a Dose
If you take your medication on a regular schedule, take the missed dose as soon as you remember. However, if it's close to the time for your next dose, skip the missed dose and resume your regular dosing schedule. Do not take two doses at the same time or take extra doses. If you take your medication as needed, do not take it more frequently than directed by your doctor.
To get the most benefit from your medication, take it exactly as directed by your doctor. Carefully read all the information provided with your prescription, and follow the instructions closely. Take your medication with meals and at bedtime, or as instructed by your doctor.
It's essential to avoid taking antacids at the same time as your medication. If you have any questions or concerns, discuss them with your doctor. To help prevent heartburn, take your medication 30 minutes before consuming foods or drinks that trigger heartburn.
Storing and Disposing of Your Medication
Store your medication at room temperature in a dry place, avoiding the bathroom. Keep all medications in a safe location, out of the reach of children and pets. Dispose of unused or expired medications properly. Do not flush them down the toilet or pour them down the drain unless instructed to do so by your doctor or pharmacist. If you're unsure about the best way to dispose of your medication, consult with your pharmacist. You may also want to check if there are drug take-back programs available in your area.
What to Do If You Miss a Dose
If you take your medication on a regular schedule, take the missed dose as soon as you remember. However, if it's close to the time for your next dose, skip the missed dose and resume your regular dosing schedule. Do not take two doses at the same time or take extra doses. If you take your medication as needed, do not take it more frequently than directed by your doctor.
Lifestyle & Tips
- Avoid foods and drinks that trigger your symptoms (e.g., spicy foods, caffeine, alcohol, fatty foods).
- Eat smaller, more frequent meals.
- Do not lie down immediately after eating; wait at least 2-3 hours.
- Elevate the head of your bed by 6-8 inches if you experience nighttime heartburn.
- Avoid smoking, as it can worsen acid reflux.
Available Forms & Alternatives
Dosing & Administration
Adult Dosing
Standard Dose:
For active duodenal ulcer: 800 mg once daily at bedtime OR 300 mg four times daily with meals and at bedtime. For maintenance: 400 mg once daily at bedtime. For GERD: 800 mg twice daily or 400 mg four times daily. For pathological hypersecretory conditions (e.g., Zollinger-Ellison Syndrome): 300 mg four times daily, may increase up to 2400 mg/day.
Dose Range:
300 - 2400 mg
Condition-Specific Dosing:
activeDuodenalUlcer:
800 mg once daily at bedtime OR 300 mg QID
maintenanceDuodenalUlcer:
400 mg once daily at bedtime
GERD:
800 mg BID or 400 mg QID
pathologicalHypersecretoryConditions:
300 mg QID, adjust as needed (up to 2400 mg/day)
Pediatric Dosing
Neonatal:
Not established (limited data, often 10-20 mg/kg/day in 2-4 divided doses, monitor closely)
Infant:
Not established (limited data, often 10-20 mg/kg/day in 2-4 divided doses, monitor closely)
Child:
20-40 mg/kg/day in 4 divided doses (max 2400 mg/day)
Adolescent:
Same as adult dosing for specific indications
Dose Adjustments
Renal Impairment:
Mild:
CrCl 20-40 mL/min: 300 mg every 12 hours
Moderate:
CrCl <20 mL/min: 300 mg every 24 hours
Severe:
CrCl <20 mL/min: 300 mg every 24 hours
Dialysis:
Administer after hemodialysis. Supplemental dose may be needed.
Hepatic Impairment:
Mild:
No specific adjustment recommended
Moderate:
No specific adjustment recommended, use with caution
Severe:
No specific adjustment recommended, use with caution; monitor for CNS effects
Pharmacology
Mechanism of Action
Cimetidine is a histamine H2-receptor antagonist. It reversibly blocks the action of histamine at the H2 receptors on the gastric parietal cells, leading to a reduction in both basal and stimulated gastric acid secretion and gastric volume. It also reduces pepsin secretion.
Pharmacokinetics
Absorption:
Bioavailability:
60-70%
Tmax:
1-2 hours
FoodEffect:
Food may slightly delay absorption but does not significantly affect the extent of absorption.
Distribution:
Vd:
0.8 L/kg
ProteinBinding:
13-25%
CnssPenetration:
Limited, but can cross the blood-brain barrier, especially with high doses or in patients with renal impairment.
Elimination:
HalfLife:
2-3 hours (prolonged in renal impairment)
Clearance:
Not available (primarily renal excretion)
ExcretionRoute:
Renal (primarily unchanged drug)
Unchanged:
50-80%
Pharmacodynamics
OnsetOfAction:
Within 30 minutes
PeakEffect:
1-2 hours
DurationOfAction:
4-6 hours
Safety & Warnings
Side Effects
Urgent Side Effects: Seek Medical Help Right Away
Although rare, this medication can cause severe and potentially life-threatening side effects. If you experience any of the following symptoms, contact your doctor immediately or seek emergency medical attention:
Signs of an allergic reaction, such as:
+ Rash
+ Hives
+ Itching
+ Red, swollen, blistered, or peeling skin with or without fever
+ Wheezing
+ Tightness in the chest or throat
+ Trouble breathing, swallowing, or talking
+ Unusual hoarseness
+ Swelling of the mouth, face, lips, tongue, or throat
Confusion
Agitation
Mood changes
Hallucinations (seeing or hearing things that are not there)
Enlarged breasts
Liver problems, which can be rare but potentially deadly. Be aware of signs such as:
+ Dark urine
+ Tiredness
+ Decreased appetite
+ Upset stomach or stomach pain
+ Light-colored stools
+ Vomiting
+ Yellow skin or eyes
Other Possible Side Effects
Like all medications, this drug can cause side effects. While many people may not experience any side effects or only minor ones, it's essential to discuss any concerns with your doctor. If you have side effects that bother you or do not go away, contact your doctor for guidance.
Reporting Side Effects
If you have questions or concerns about side effects, you can:
Call your doctor for medical advice
Report side effects to the FDA at 1-800-332-1088
Submit a report online at https://www.fda.gov/medwatch
Although rare, this medication can cause severe and potentially life-threatening side effects. If you experience any of the following symptoms, contact your doctor immediately or seek emergency medical attention:
Signs of an allergic reaction, such as:
+ Rash
+ Hives
+ Itching
+ Red, swollen, blistered, or peeling skin with or without fever
+ Wheezing
+ Tightness in the chest or throat
+ Trouble breathing, swallowing, or talking
+ Unusual hoarseness
+ Swelling of the mouth, face, lips, tongue, or throat
Confusion
Agitation
Mood changes
Hallucinations (seeing or hearing things that are not there)
Enlarged breasts
Liver problems, which can be rare but potentially deadly. Be aware of signs such as:
+ Dark urine
+ Tiredness
+ Decreased appetite
+ Upset stomach or stomach pain
+ Light-colored stools
+ Vomiting
+ Yellow skin or eyes
Other Possible Side Effects
Like all medications, this drug can cause side effects. While many people may not experience any side effects or only minor ones, it's essential to discuss any concerns with your doctor. If you have side effects that bother you or do not go away, contact your doctor for guidance.
Reporting Side Effects
If you have questions or concerns about side effects, you can:
Call your doctor for medical advice
Report side effects to the FDA at 1-800-332-1088
Submit a report online at https://www.fda.gov/medwatch
Seek Immediate Medical Attention If You Experience:
- Black, tarry stools or vomit that looks like coffee grounds (signs of bleeding in the stomach or intestines)
- Severe stomach pain
- Difficulty swallowing
- Unexplained weight loss
- Yellowing of the skin or eyes (jaundice)
- Unusual confusion, disorientation, or hallucinations (especially in older adults or those with kidney problems)
- Unusual bruising or bleeding
- Persistent fever or sore throat
Before Using This Medicine
Before Taking This Medication: Important Information to Share with Your Doctor
It is essential to inform your doctor about the following:
Any allergies you have, including allergies to this medication, its components, or other substances, such as foods or drugs. Be sure to describe the symptoms you experienced.
If you are currently taking dofetilide, as this may interact with the medication.
If you are breast-feeding, as you should not breast-feed while taking this medication.
Additionally, to ensure your safety, it is crucial to provide your doctor and pharmacist with a comprehensive list of:
All prescription and over-the-counter (OTC) medications you are taking
Any natural products or vitamins you are using
Your existing health problems
This information will help your doctor determine if it is safe for you to take this medication with your other medications and health conditions. Never start, stop, or change the dose of any medication without first consulting your doctor.
It is essential to inform your doctor about the following:
Any allergies you have, including allergies to this medication, its components, or other substances, such as foods or drugs. Be sure to describe the symptoms you experienced.
If you are currently taking dofetilide, as this may interact with the medication.
If you are breast-feeding, as you should not breast-feed while taking this medication.
Additionally, to ensure your safety, it is crucial to provide your doctor and pharmacist with a comprehensive list of:
All prescription and over-the-counter (OTC) medications you are taking
Any natural products or vitamins you are using
Your existing health problems
This information will help your doctor determine if it is safe for you to take this medication with your other medications and health conditions. Never start, stop, or change the dose of any medication without first consulting your doctor.
Precautions & Cautions
It is essential to inform all your healthcare providers, including doctors, nurses, pharmacists, and dentists, that you are taking this medication. If you experience any of the following symptoms, contact your doctor immediately: throat pain, chest pain, severe abdominal pain, difficulty swallowing, or signs of a bleeding ulcer, such as black, tarry, or bloody stools, vomiting blood, or vomit that resembles coffee grounds, as these may be indicative of a more serious health issue.
When taking this medication, it is crucial to coordinate with other medications you are currently using, as they may need to be taken at a different time. Consult with your doctor or pharmacist to determine the optimal schedule for taking your medications.
If you are 50 years or older, exercise caution when using this drug, and discuss any concerns with your doctor. Additionally, if you are pregnant or planning to become pregnant, inform your doctor, as you will need to discuss the potential benefits and risks associated with using this medication during pregnancy.
When taking this medication, it is crucial to coordinate with other medications you are currently using, as they may need to be taken at a different time. Consult with your doctor or pharmacist to determine the optimal schedule for taking your medications.
If you are 50 years or older, exercise caution when using this drug, and discuss any concerns with your doctor. Additionally, if you are pregnant or planning to become pregnant, inform your doctor, as you will need to discuss the potential benefits and risks associated with using this medication during pregnancy.
Overdose Information
Overdose Symptoms:
- Drowsiness
- Confusion
- Disorientation
- Slurred speech
- Tachycardia (rapid heart rate)
- Respiratory depression
- Ataxia (loss of coordination)
What to Do:
Seek immediate medical attention. Call 911 or Poison Control at 1-800-222-1222. Treatment is supportive and symptomatic.
Drug Interactions
Major Interactions
- Warfarin (increased INR, bleeding risk)
- Phenytoin (increased phenytoin levels, toxicity)
- Theophylline (increased theophylline levels, toxicity)
- Procainamide (increased procainamide levels, toxicity)
- Lidocaine (increased lidocaine levels, toxicity)
- Metformin (increased metformin levels, lactic acidosis risk)
- Dofetilide (increased dofetilide levels, QT prolongation, Torsades de Pointes)
Moderate Interactions
- Calcium channel blockers (e.g., nifedipine, diltiazem - increased levels)
- Tricyclic antidepressants (e.g., imipramine, amitriptyline - increased levels)
- Benzodiazepines (e.g., diazepam, chlordiazepoxide - increased levels, prolonged sedation)
- Sulfonylureas (e.g., glipizide, glyburide - increased hypoglycemic effect)
- Quinidine (increased quinidine levels)
- Ethanol (increased blood alcohol levels)
- Opioids (e.g., morphine - increased respiratory depression)
Minor Interactions
- Antacids (may decrease cimetidine absorption if given concurrently; separate by 1-2 hours)
- Iron salts (may decrease absorption of iron)
Monitoring
Baseline Monitoring
Renal function (serum creatinine, eGFR)
Rationale: Cimetidine is primarily renally eliminated; dose adjustment is required in renal impairment.
Timing: Prior to initiation of therapy.
Routine Monitoring
Symptom relief (e.g., heartburn, dyspepsia)
Frequency: Regularly throughout treatment
Target: Resolution or significant improvement of symptoms
Action Threshold: Lack of symptom improvement or worsening symptoms may indicate need for dose adjustment or alternative therapy.
Renal function (serum creatinine, eGFR)
Frequency: Periodically, especially in elderly or those with pre-existing renal impairment
Target: Stable within patient's baseline or acceptable limits
Action Threshold: Significant decline in renal function may necessitate dose reduction.
INR (if on warfarin)
Frequency: More frequently upon initiation or dose change of cimetidine, then as clinically indicated
Target: Therapeutic range for warfarin indication
Action Threshold: INR outside therapeutic range requires warfarin dose adjustment.
Drug levels (e.g., phenytoin, theophylline, procainamide)
Frequency: As clinically indicated, especially upon initiation or dose change of cimetidine
Target: Therapeutic range for the co-administered drug
Action Threshold: Levels outside therapeutic range require dose adjustment of the co-administered drug.
Symptom Monitoring
- Persistent or worsening abdominal pain
- Black, tarry stools or 'coffee-ground' vomit (signs of GI bleeding)
- Unusual confusion, disorientation, or hallucinations (especially in elderly or renally impaired patients)
- Unexplained fever, sore throat, or unusual bruising/bleeding (signs of blood dyscrasias)
- Gynecomastia or impotence (in men, with long-term, high-dose use)
Special Patient Groups
Pregnancy
Cimetidine is classified as Pregnancy Category B. Studies in animals have not shown harm to the fetus, but there are no adequate and well-controlled studies in pregnant women. It should be used during pregnancy only if clearly needed.
Trimester-Specific Risks:
First Trimester:
Generally considered low risk, but use only if clearly indicated.
Second Trimester:
Generally considered low risk.
Third Trimester:
Generally considered low risk.
Lactation
Cimetidine is excreted into breast milk. The American Academy of Pediatrics considers it compatible with breastfeeding. However, monitor the infant for potential side effects such as gastrointestinal disturbances (e.g., diarrhea) or CNS effects.
Infant Risk:
L2 (Safer) - Low risk of adverse effects in breastfed infants. Monitor for potential GI or CNS effects.
Pediatric Use
Dosing is established for children, but caution is advised in neonates and infants due to limited data and potential for increased CNS effects. Renal function should be monitored, and doses adjusted accordingly.
Geriatric Use
Elderly patients are more susceptible to CNS side effects (e.g., confusion, delirium, hallucinations) due to age-related decline in renal function and potential for polypharmacy. Lower doses and careful monitoring are recommended. Dose adjustment is often necessary based on renal function.
Clinical Information
Clinical Pearls
- Cimetidine is known for its significant drug interaction potential due to its inhibition of multiple CYP450 enzymes (especially CYP1A2, 2C9, 2D6). Always review patient's medication list for potential interactions.
- Long-term, high-dose use of cimetidine in men has been associated with gynecomastia and impotence, likely due to its anti-androgenic effects.
- While generally well-tolerated, CNS side effects (confusion, dizziness) are more common in elderly patients or those with renal/hepatic impairment.
- Cimetidine can interfere with the absorption of drugs that require an acidic gastric environment (e.g., ketoconazole, atazanavir); separate administration times or consider alternative acid suppressants.
Alternative Therapies
- Other H2-receptor antagonists (e.g., famotidine, ranitidine [if available], nizatidine)
- Proton pump inhibitors (PPIs) (e.g., omeprazole, lansoprazole, pantoprazole, esomeprazole, rabeprazole)
- Antacids (for symptomatic relief)
- Sucralfate (for ulcer treatment)
Cost & Coverage
Average Cost:
Typically low (generic) per 30 tablets
Generic Available:
Yes
Insurance Coverage:
Tier 1 or Tier 2 (most insurance plans)
General Drug Facts
If your symptoms or health issues persist or worsen, it is essential to contact your doctor promptly. To ensure safe and effective treatment, never share your medication with others or take someone else's medication. Some medications may come with an additional patient information leaflet, so it is a good idea to consult with your pharmacist. If you have any questions or concerns about this medication, do not hesitate to discuss them with your doctor, nurse, pharmacist, or other healthcare provider. In the event of a suspected overdose, immediately call your local poison control center or seek emergency medical attention. When reporting the incident, be prepared to provide detailed information, including the name of the medication taken, the amount, and the time it occurred.