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Patients taking cimetidine (generic by prescription; TAGAMET HB and generics over the counter) should be aware that it has clinically important and potentially dangerous interactions with many other medications.
Cimetidine is a stomach-acid–suppressing drug that was first approved by the Food and Drug Administration in 1977. It belongs to the family of medicines called histamine-2 receptor blockers.[1] Cimetidine is approved for the treatment of duodenal ulcers and benign gastric ulcers,...
Patients taking cimetidine (generic by prescription; TAGAMET HB and generics over the counter) should be aware that it has clinically important and potentially dangerous interactions with many other medications.
Cimetidine is a stomach-acid–suppressing drug that was first approved by the Food and Drug Administration in 1977. It belongs to the family of medicines called histamine-2 receptor blockers.[1] Cimetidine is approved for the treatment of duodenal ulcers and benign gastric ulcers, as well as conditions that are caused by excessive stomach acid (such as Zollinger-Ellison syndrome) or by a backflow of acid from the stomach (gastroesophageal reflux disease). Cimetidine is also available over the counter for relief and prevention of heartburn linked to indigestion or sour stomach.[2]
Drugs whose effects are increased by cimetidine
Cimetidine can inhibit liver enzymes involved in the breakdown of many other drugs. As a result, concomitant use (at the same time) of cimetidine with these other drugs can increase the blood levels of these drugs substantially (see Table 1, below, for examples of oral drugs).[3] The list of these oral drugs includes drugs for depression, heart-rhythm disorders, hypertension (high blood pressure), asthma and malaria.
For some of these drugs, the risk of toxicity is so great that they should not be taken concomitantly with cimetidine.
Table 1. Examples of Oral Drugs Whose Effects May Be Increased by Cimetidine[4],[5]
| Generic Name | Brand Name(s) | Drug Class |
|---|---|---|
| alprazolam* | XANAX, XANAX XR | Benzodiazepine |
| amiodarone** | PACERONE | Heart-rhythm disorder drug |
| chloroquine** | generic only | Antimalarial drug |
| diltiazem** | CARDIZEM, CARTIA XT, TAZTIA XT, TIAZAC | Calcium channel blocker |
| duloxetine*** | CYMBALTA | Antidepressant |
| flecainide | generic only | Abnormal heart-rhythm drug |
| hydroxychloroquine | PLAQUENIL | Drug for malaria, rheumatoid arthritis and lupus erythematosus |
| labetalol | TRANDATE | Beta (and alpha) blocker |
| lomitapide*** | JUXTAPID | Cholesterol-lowering drug |
| metronidazole** | FLAGYL | Antibiotic drug |
| nifedipine | PROCARDIA,*** PROCARDIA XL** | Calcium channel blockers for angina and hypertension |
| phenytoin | DILANTIN, PHENYTEK | Antiseizure medication |
| propranolol | HEMANGEOL, INDERAL LA, INNOPRAN XL | Beta blocker |
| quinidine** | generic only | Heart-rhythm disorder drug |
| theophylline** | ELIXOPHYLLIN, THEO-24 | Asthma drug |
| tizanidine** | ZANAFLEX | Drug for spasticity |
| warfarin | JANTOVEN | Blood thinner |
| zaleplon*** | SONATA | Z-drug sleeping pill |
*Designated as Do Not Use Except For Panic Disorder by Worst Pills, Best Pills News
**Designated as Limited Use by Worst Pills, Best Pills News
***Designated as Do Not Use by Worst Pills, Best Pills News
Notable adverse effects due to drug interactions with cimetidine[6],[7],[8]
Fatal heart-rhythm abnormalities
A few medications, when taken concomitantly with cimetidine, can cause serious adverse cardiovascular events, including QT prolongation. QT prolongation is a change in the electrical activity of the heart that can lead to a heart-rhythm disturbance called torsade de pointes, which can cause cardiac arrest and sudden death. These medications include citalopram (CELEXA), dofetilide (TIKOSYN) and pimozide (generic only).
Respiratory depression
Concomitant use of cimetidine with opioids, such as oxymorphone (generic only), meperidine (generic only) or morphine (MS CONTIN), can increase the effects of these drugs and lead to an increased risk of central nervous system and respiratory depression.
Urinary retention
When taken concomitantly with tricyclic antidepressants — including amitriptyline (generic only), amoxapine (generic only), desipramine (NORPRAMIN), doxepin (SILENOR ) or imipramine (TOFRANIL) — cimetidine can increase blood levels of these drugs. The increased blood levels of the drugs can cause symptoms such as blurred vision, dry mouth and urinary retention (inability to empty the bladder completely).
Drugs whose effects are decreased by cimetidine
Because cimetidine reduces the amount of stomach acid, it also can change how some medications are absorbed and may make them less effective (see Table 2, below). Examples include medications used to treat fungal or viral infections, high blood pressure and heart failure and drugs that prevent platelet aggregation.
Table 2. Examples of Oral Drugs Whose Effects May Be Decreased by Cimetidine[9]
| Generic Name | Brand Name(s) | Drug Class |
|---|---|---|
| atazanavir | REYATAZ | Antiviral drug for HIV infection |
| clopidogrel* | PLAVIX | Antiplatelet drug |
| itraconazole** | SPORANOX, TOLSURA | Antifungal drug |
| ketoconazole*** | generic only | Antifungal drug |
| posaconazole | NOXAFIL | Antifungal drug |
| sparsentan* | FILSPARI | Angiotensin receptor blocker |
*Designated as Limited Use by Worst Pills, Best Pills News
**Designated as Do Not Use except for serious fungal infections by Worst Pills, Best Pills News
***Designated as Do Not Use by Worst Pills, Best Pills News
What You Can Do
If you need treatment with cimetidine, review all your other medications with your doctor to identify potentially significant drug interactions. If you are taking a medication that interacts with cimetidine, your doctor may recommend stopping or adjusting the dosage of the interacting drug or may advise you to take a drug other than cimetidine for your condition. Be aware that drugs not listed in this article also may have dangerous interactions with cimetidine.
References
[1] Mylan Pharmaceuticals. Label: cimetidine. July 2019. https://dailymed.nlm.nih.gov/dailymed/fda/fdaDrugXsl.cfm?setid=06c0a509-026f-44e0-9975-a94a8de51d43&type=display. Accessed June 6, 2023.
[2] Medtech Products. Label: cimetidine (TAGAMET). Accessed May 24, 2023. https://dailymed.nlm.nih.gov/dailymed/fda/fdaDrugXsl.cfm?setid=e6401e0a-8612-42e8-bf89-2d67243f28dc&type=display. Accessed June 6, 2023.
[3] Mylan Pharmaceuticals. Label: cimetidine. July 2019. https://dailymed.nlm.nih.gov/dailymed/fda/fdaDrugXsl.cfm?setid=06c0a509-026f-44e0-9975-a94a8de51d43&type=display. Accessed June 20, 2023.
[4] IBM Micromedex. Drug interactions. http://www.micromedexsolutions.com/home/dispatch. Search term: “Cimetidine.” Accessed June 6, 2023.
[5] Mylan Pharmaceuticals. Label: cimetidine. July 2019. https://dailymed.nlm.nih.gov/dailymed/fda/fdaDrugXsl.cfm?setid=06c0a509-026f-44e0-9975-a94a8de51d43&type=display. Accessed June 6, 2023.
[6] IBM Micromedex. Drug interactions. http://www.micromedexsolutions.com/home/dispatch. Search term: “Cimetidine.” Accessed June 6, 2023.
[7] Medscape. cimetidine (Rx). https://reference.medscape.com/drug/tagamet-cimetidine-341984#0. Accessed June 6, 2023.
[8] Mylan Pharmaceuticals. Label: cimetidine. July 2019. https://dailymed.nlm.nih.gov/dailymed/fda/fdaDrugXsl.cfm?setid=06c0a509-026f-44e0-9975-a94a8de51d43&type=display. Accessed June 6, 2023.
[9] IBM Micromedex. Drug interactions. http://www.micromedexsolutions.com/home/dispatch. Search term: “Cimetidine.” Accessed June 6, 2023.
