The Facts About H2 Blockers

About 15 million Americans take proton pump inhibitors (PPIs), although it's been estimated as many as two-thirds of those people take them when they shouldn't. Learn more about PPIs and histamine type 2 (H2) blockers, what they do and what they don't do, and whether you should be taking them at all.

Acid-peptic diseases stem from an overabundance of acid in the duodenal and/or gastric mucosa. They include dyspepsia, gastroesophageal reflux disease (GERD), heartburn and peptic ulcer disease (PUD).

Selective histamine type 2 receptor blockers (H2 blockers, also known as H2 antagonists) are popular anti-ulcer agent medications used in the treatment of most of these conditions. H2 blockers are available over the counter or with a prescription. 

In the United States, four different H2 receptor blockers are accessible: ranitidine, nizatidine, famotidine and cimetidine. All have similar drug profiles and share similar clinical evidence, capabilities and side effects.

The goal of H2 antagonists is to circumvent the overproduction of gastric acid. They do this by attaching to the basolateral surface of gastric parietal cells via H2 receptors, which inhibits the generation and release of gastric acid. Rather than being metabolized in the blood, H2 blockers are broken down by the liver.

One pivotal aspect of how H2 antagonists work is their selectivity. They are crafted to be minimally effective on histamine type 1 receptors. These receptors are barricaded by typical antihistamines, whose purpose is associated not with gastric acid production but with treating allergic reactions.

H2 blockers are designed to treat certain ailments within the gastrointestinal system, such as:

• Esophagitis and other minor upper gastrointestinal symptoms
• GERD
• Heartburn
• Peptic ulcer disease

Additionally, they can abate current gastric or duodenal ulcers and prevent future stress ulcers.

When heartburn is unresponsive to lifestyle measures, H2 antagonists are shown to be sufficient treatment in most cases. Though dyspepsia, or what's commonly called "indigestion," falls under the acid-peptic disease category, H2 blockers are an inappropriate treatment because dyspepsia is unimpacted by gastric acid levels. The same goes for any other gastrointestinal condition not related to the acid.

Similar to H2 antagonists, proton pump inhibitors aim to reduce gastric acid production. However, where H2 blockers attach to receptors to stifle gastric acid generation, PPIs take it a step further and deactivate the proton pumps entirely. This makes PPIs the stronger option of the two and is currently the best choice for severe cases of esophagitis and heartburn. 

Despite their general inferiority compared to PPIs, H2 antagonists are still effective for treating certain gastrointestinal problems and can reduce daily acid secretions by about 70 percent.

Side effects from H2 antagonists are few and far between and rarely life-threatening. Compared to the illnesses they aim to treat, possible effects are minor. The most commonly reported side effects are:

• Constipation
• Diarrhea
• Drowsiness
• Fatigue
• Headache
• Muscle aches

Another benefit of H2 antagonists is their low risk of impairing central nervous system function, which can happen with medications used to treat acid-peptic diseases. They don't easily bypass the blood-brain barrier, which acts as a high-tech filter for the brain, protecting it from bacteria and/or toxins in the bloodstream that could cause an infection of the brain.

Along with the rare but serious side effect of liver illness, improper use of H2 blockers (particularly famotidine) can cause medical consequences. 

Although these medications can be effective for many gastrointestinal diseases/conditions related to excess acid production, there is some research that indicates they can have negative effects on patients with other GI diseases. For example, people with ulcerative colitis (UC) develop sores on their digestive tracts because of inflammation within the lining of the large intestine and rectum, which subsequently alters the area's microbiome. 

Some research suggests H2 antagonists and PPIs may increase the frequency of ulcerative colitis flares, which could be related to a combination of alteration in the microbiome and with acid.

Sexual side effects of H2 blockers for women are scarcely reported, and problems seem to occur much more frequently in men. The duration and dosage of medication have a positive correlation to the incidence of sexual side effects, and the most commonly reported problem is erectile dysfunction (ED). 

Along with ED, chronic usage of H2 antagonists has been linked to reduced sperm count and testosterone, male breast enlargement and decreased libido. Research attributes these links to the medication's effect on the endocrine system and the interruption of H2 receptors needed for erections.

H2 blockers may contribute to ED because histamines act as neurotransmitters to aid in the gaining and maintaining of an erection. Additionally, some H2 antagonists lead to reduced testosterone levels, which can make ED more common.

Though the risk does exist, it is important to continue taking medications to treat gastrointestinal diseases as your doctor advises. Always assess potential risks and benefits with your doctor before starting or quitting medications.

Your sexual health doesn't have to take a hit just because you suffer from heartburn. If you have acid-neutralizing medications, take them regularly and on time to reduce the chances of having a flare-up when you want to get intimate. If you have GERD, use sex positions that allow gravity to pull the acid back down into the esophagus. 

If you are or may become pregnant, or you're breastfeeding, alert a doctor immediately because many medications that target acid-peptic diseases can harm an infant. Try taking an over-the-counter antacid first and discuss other medications with your healthcare provider.

If you're looking for quick, short-term relief, you can find a number of antacids at your local pharmacy. Granted you have a compatible condition, PPIs are an excellent alternative to H2 antagonists and are better for chronic diseases, though the effects may be delayed for a few days after use. 

No matter which alternative you choose, make sure to double-check with a doctor to avoid harmful drug interactions. Alternatively, there are natural remedies that aim to neutralize acid and microbiomes. Some people have success with probiotics, apple cider vinegar and aloe vera juice or capsules.

If you have new or worsening gastrointestinal symptoms, err on the side of caution and speak to your general practitioner, who may refer you to a specialist. Some symptoms of concern include bad breath, trouble breathing and the need for frequent antacid use. 

Though most people experience nausea, gas, constipation and diarrhea at some point, if you notice the conditions are happening at once and are chronic, you should make an appointment to see your healthcare provider immediately. These symptoms could be indicative of serious gastrointestinal health problems such as Crohn's disease, a stomach ulcer or irritable bowel syndrome (IBS).

What are the most common H2 blockers?

In the United States, the options include four different H2 receptor blockers: ranitidine, nizatidine, famotidine and cimetidine, all with similar drug profiles. A prescription is often required depending on the formulation and strength. Over-the-counter alternatives also can be useful for temporary relief but are not built for long-term use.

Are H2 blockers the same as antihistamines?

No. Antihistamines are medications that impact histamine type 1 (H1) receptors and are related to allergic conditions and reactions. They have little or no impact on gastric acid quantities and usually affect the nose. H2 blockers are designed for acid-peptic diseases, such as gastrointestinal ulcers, gastroesophageal reflux disease, heartburn and peptic ulcer disease, all of which are related to the digestive tract.

Who should not take H2 blockers?

H2 blockers have the potential to cause side effects to the central nervous system in people with certain preexisting conditions. Typically, people older than age 50 and people with liver impairment(s) and/or kidney problems should avoid H2 antagonists. Talk to your doctor about drug or supplement interactions, and especially don't take H2 blockers if you are or may become pregnant or are breastfeeding, as they may harm an infant.