8 Cimetidine Side Effects and How to Manage Them

Sometimes, you just need to treat yourself. That could be an indulgent meal at your favorite restaurant or an extra scoop at the ice cream joint down the street. Whatever the case, if it isn't part of your typical diet, you might find yourself paying for that treat with some nasty heartburn a few hours later.

Many of us have found ourselves in this situation - scrambling for an antacid and hoping for some instant relief. But not all acid reducers are the same. Cimetidine (Tagamet) is part of a family of medications called histamine-2 receptor antagonists (H2 blockers). Cimetidine is typically recommended for stomach ulcers and acid reflux, and it lasts longer than short-acting antacids like calcium carbonate (Tums) and calcium carbonate / magnesium hydroxide (Rolaids).

Cimetidine is available as a prescription and as an over-the-counter (OTC) medication. Many people don't think about possible side effects when reaching for such an accessible product. But it's important to remember that there are some potential side effects and risks.

Cimetidine side effects at a glance

Cimetidine is a well-tolerated medication overall. When cimetidine side effectsdo occur, they're typically mild. And if you only take cimetidine occasionally for heartburn, you're even less likely to experience side effects.

Some of the more common cimetidine side effects include:

• Diarrhea

• Headaches

• Dizziness

• Sleepiness

• Liver problems

• Kidney problems

• Rash

Rare but potentially serious cimetidine side effects include:

• Confusion

• Agitation

• Changes in behavior

• Hallucinations

• Joint and muscle pain

• Breast enlargement in men

• Decreased blood cell counts

• Pancreatic inflammation

• Kidney inflammation

• Fever

• Hair loss

• Vitamin deficiency

• Severe skin reactions

• Allergic reactions

Here, we'll dive deeper into eight notable cimetidine side effects and how to navigate them.

1. Diarrhea

Diarrhea from cimetidine tends to be mild. It's generally manageable with temporary diet changes and OTC medications.

Here are a few diarrhea management strategies you can try:

• Avoid fatty, high-fiber, or fried foods. Instead, consider eating bland foods for a short time, including those that fit into the BRAT diet.

• Drink plenty of clear fluids, including water, electrolyte drinks, and broths, to prevent dehydration.

• Take an OTC antidiarrheal medication like loperamide (Imodium A-D) with your healthcare professional's OK.

If you're having trouble drinking enough fluids, are feeling dizzy or extremely tired, or don't see your symptoms improve, make sure to reach out to your healthcare professional. They can determine if you need to receive IV fluids or if you should take a prescription antidiarrheal medication. They can also let you know if it'd be wise to switch to an alternative acid-lowering medication.

2. Headaches

Headaches with cimetidine are a little more common than diarrhea. Headaches related to the medication can range from mild to severe, and are more common with higher cimetidine dosages (1,600 mg per day). Higher dosages of cimetidine are mostly used to treat stomach ulcers.

To manage mild-to-moderate headaches, you can try:

• Reducing stress with methods such as progressive muscle relaxation, meditation, and breathing exercises

• Getting enough sleep

• Avoiding headache-causing foods and beverages, such as foods with nitrates and alcohol

• Taking an OTC pain reliever, such as acetaminophen (Tylenol) or ibuprofen (Advil)

If you're experiencing a severe headache - with or without related symptoms such as a stiff neck, fever, or vision changes - visit the nearest ER right away.

3. Dizziness or drowsiness

Mild dizziness or drowsiness may occur in people who take at least 800 mg of cimetidine per day. These side effects are less common with lower dosages.

Dizziness can make you lose your balance and put you at risk for falls. If you're an older adult, this can be a big deal. If you hit your head or injure yourself, a fall could send you to the hospital. Drowsiness can also pose a serious issue. Being too sleepy during the day can not only affect your productivity, it can also be dangerous if you feel drowsy while driving or doing other activities that require focus.

The good news is that dizziness and drowsiness related to cimetidine are usually mild and temporary. If you're 65 years or older, your healthcare professional may start you with a lower dosage to help minimize these side effects. You may also receive a lower dosage if your kidneys aren't functioning at the top of their game. Cimetidine is eliminated from the body through the kidneys, so this could cause the medication to build up in your system. And that could increase your risk for side effects.

4. Confusion

Cimetidine is able to cross the blood-brain barrier, a layer of blood vessels that tightly regulate what's allowed into the brain. This is the main reason why brain-related side effects, such as confusion, agitation, and hallucinations, are possible with cimetidine.

Reports of cimetidine-related confusion are more common among older adults, those with kidney problems, and hospitalized people. If you're in a high-risk group, your healthcare professional may recommend a different acid-lowering medication, such as famotidine (Pepcid) or omeprazole (Prilosec).

If cimetidine is the preferred treatment, you'll likely receive a lower dosage to prevent confusion or brain-related side effects.

5. Muscle and joint pain

Muscle and joint pain are common side effects of many medications. While these side effects are relatively rare with cimetidine, they may happen in people who have existing joint inflammation. The good news is that these effects are reversible and can usually be managed with a decrease in dosage.

If your healthcare professional wants you to keep taking your current dosage, here are a few home remedies you can try:

• Take an OTC pain reliever that also treats inflammation, such as ibuprofen or naproxen (Aleve).

• Apply cool or hot compresses to the affected muscles or joints.

• Try booking a massage to ease sore muscles.

If none of the above strategies provide relief and the pain is interfering with your daily life, reach out to your healthcare professional. They may consider switching you to a different medication.

6. Skin rashes

A mild rash is another potential cimetidine side effect. Any time you develop a rash with a new medication, it's best to reach out to your healthcare professional for guidance. They'll likely want to examine the rash and make sure it's not getting worse or a potential sign of an allergic reaction.

If your healthcare professional decides it's OK for you to keep taking cimetidine, you might try these strategies to help with your rash:

• Apply an OTC topical corticosteroid like hydrocortisone to the affected area.

• Take an OTC antihistamine like diphenhydramine (Benadryl) at night if the rash is itchy and keeps you awake.

• Apply an unscented moisturizer if the rash is dry and scaly.

Good to know: In rare cases, rashes can progress to more serious skin conditions, including Stevens-Johnson syndrome (SJS), toxic epidermal necrolysis (TEN), and erythema multiforme. These are life-threatening conditions that can affect multiple organs in the body. Go to the nearest ER if you notice skin blistering or peeling alongside fever or flu-like symptoms.

7. Breast enlargement in men

In rare cases, cimetidine can cause a side effect called gynecomastia, or breast enlargement in men. Other symptoms that can come along with gynecomastia are nipple tenderness and breast pain.

It's worth noting that gynecomastia happens with much higher cimetidine dosages (almost three times higher) than what is typically used for heartburn or stomach ulcers. So it's unlikely that you'll experience this side effect.

You can technically have surgery for gynecomastia, but it's expensive and generally not necessary with cimetidine use. If you do happen to develop this rare side effect, reach out to your healthcare professional to discuss a lower dosage or alternative medication.

8. Liver changes

If you're taking cimetidine for more than 1 month, you may experience minor increases in your liver enzymes. These are proteins in your liver that play a role in metabolizing medications and other important functions in your body.

Elevated liver enzymes can be a sign of liver damage. Up to 4% of people experienced increased liver enzymes in initial studies of cimetidine. But these increases didn't cause symptoms and typically resolved on their own.

Severe liver issues with cimetidine are rare, and they can typically be reversed by stopping the medication. Reach out to your healthcare professional if you notice signs of liver toxicity such as yellowing of the skin, abdominal pain, or dark urine.

Good to know: Your liver produces enzymes (proteins) that are important for breaking down (metabolizing) many medications. Cimetidine can cause drug interactions by blocking the function of these enzymes. Reach out to your pharmacist before starting cimetidine to determine if it has the potential to interact with any of your existing medications.