Proton Pump Inhibitors (PPI), H2 Blockers and antacids: A review

 

Medications for acid reflux, heartburn, and GERD (gastroesophageal reflux disease) come in three types: H2 blockers, proton pump inhibitors (PPIs), and antacids. They all work differently and are geared towards either prevention or quick relief. H2 blockers and proton pump inhibitors work better than antacids, but if you need something for very quick relief, antacids are an option. Antacids don’t do anything to prevent GERD (gastroesophageal reflux disease), but they can be used on demand for symptom relief. They are cheap and available over the counter.H2 blockers (histamine blockers) block one of the first stimuli for acid production. PPIs block the final step in the pathway of acid secretion in the stomach. In other words, the acid which has been produced (which may be reduced due to an H2 blocker) is prevented from arriving in the stomach. Of the three classes, antacids are the fastest acting. They start providing relief to the patient within five minutes.

The Global Market is expected to grow at a compound annual growth rate (CAGR) of 3.6% during the forecasting period (2021-2026). Rising incidence of GERD (gastroesophageal reflux disease) is the dominating factor propelling the global antacids market. Based on formulation type, the antacids drugs are segmented into tablet, liquid and powder. However, liquids and tablets segment are expected to grow at a high rate over the period of forecast. Increased use of antacids for treating GERD (gastroesophageal reflux disease) will create awareness of antacids among consumers.

Antacids are the over-the-counter medications used in neutralizing the stomach acid. They mainly work by reducing or preventing the secretion of stomach acids. They are mostly used in treating acid reflux, heartburn, indigestion. Growing prevalence of GERD (gastroesophageal reflux disease) and peptic ulcers and increasing side-effects related to non-steroidal anti-inflammatory drugs is one of the primary drivers of the market, creating lucrative opportunities for the pharmaceutical companies to manufacture different drugs to meet the demand.

However, alternative treatment for antacids and increased side-effects related to antacids are hampering the market. For instance, alternative treatments which are likely to restrict the market for antacids include acupuncture, melatonin, hypnotherapy, herbal remedies, baking soda and lifestyle changes. Also, side effects related to antacids include dose-dependent rebound hyperacidity, milk-alkali syndrome, aluminium intoxication, osteomalacia, and hypophosphatemia are restraining the market growth.

Histamine-2(H2) blockers:

H2 blockers are sometimes called H2 receptor antagonists, or H2RAs. They reduce the amount of acid that the stomach produces. H2 blockers (histamine blockers) block one of the first stimuli for acid production. H2 blockers work by blocking the histamine receptors in parietal cells (Parietal cells are acid-producing cells in the lining of the stomach) to decrease the amount of acid produced (although there are other stimuli so that some acid is still produced). H2RAs are known to decrease gastric acid secretion in a reversible fashion by blocking the action of histamine on the H2 receptors of the gastric parietal cells. This can help treat many common health issues, including GERD (gastroesophageal reflux disease), gastric ulcers, and occasional heartburn. They start providing relief to the patient within one hour. It lasts for about 9-12 hours.

H2RAs can be utilized as a maintenance option in patients who have symptoms of GERD (gastroesophageal reflux disease) but do not suffer from erosive esophagitis. While H2RAs are more efficacious than antacids in the resolution of GERD (gastroesophageal reflux disease) symptoms, there are also disadvantages associated with long-term use of H2RAs. Some patients may develop tolerance with a decreased efficacy observed after 3 to 4 weeks of treatment. Other adverse effects noted with H2RAs include rare abnormalities in complete blood count (CBC) results, liver function test irregularities, and headache.

Proton Pump Inhibitors (PPIs):

Proton pump inhibitors segment is expected to grow at a significant rate over the period of forecast. This is owing to Prescription PPI’s, easy availability of Over - the - counter (OTC) PPI’s. Due to the acid-suppressing effects, they are approved for several short-term indications like GERD, erosive esophagitis and duodenal and gastric ulcers. Long term indications include NSAID’s associated gastric ulcers, hypersecretory conditions, and maintenance of healing erosive esophagitis. For instance, the currently available PPI’s include omeprazole, lansoprazole, pantoprazole, rabeprazole, esomeprazole, dexlansoprazole and omeprazole with sodium bicarbonate etc. They can take up to 4 days to take effect. It lasts about in 24 hrs up to 3 days. PPIs block the proton pump that pumps protons (H+) into the stomach in exchange for potassium. H+ is an acid. PPIs yield greater acid suppression than H2 blockers. This is due to the fact that other stimuli, in addition to histamine 2, stimulate acid production in the stomach and H2-blockers only block histamine 2. PPIs provide faster relief than antacids, H2RAs, or prokinetic agents with regard to symptom relief and long-term healing of erosive esophagitis. All PPIs except tenatoprazole have short half-lives (about 1 hour) and all have good oral bioavailability. Acid suppression studies comparing omeprazole, lansoprazole, rabeprazole, and pantoprazole show equivalent efficacy. Esomeprazole and tenatoprazole have stronger acid suppression, with a longer period of intragastric pH greater than 4.

For structure of PPIs refer to below image:

Mechanisms of failure of PPIs include compliance, improper dosing timing, weakly acidic reflux, delayed gastric emptying, nocturnal reflux, residual acid reflux, oesophageal hypersensitivity, and reduced PPI bioavail-ability. For most patients, PPI therapy is well tolerated, but adverse effects are associated with PPIs and include Clostridium-difficile–associated diarrhoea, pneumonia, bone fractures, rebound hypersecretion, hypomagnesemia, vitamin B₁₂ deficiency, and possible drug interactions.

Antacids:

Of the three classes, antacids are the fastest acting. They start providing relief to the patient within five minutes. As such, should be used as needed (on-demand) for breakthrough symptoms that occur ideally less than once per week. They don’t prevent GERD. They simply neutralize stomach pH decreasing the exposure of the oesophageal mucosa to acid from the stomach during episodes of reflux. Antacids only work for 30 to 60 minutes and may cause side effects like constipation or diarrhea depending on which antacid you use.

Conclusions:

Of the three, PPIs are highly effective drugs that have revolutionized the management of acid-related disorders during the last two decades. Launch of omeprazole in 1988 introduced a conceptually new approach of inhibition of proton pump in the management of acid related disorders. Several new drugs are currently being investigated to vide a significant advance on current treatments. Some of them have already reached clinical testing while some other are still in preclinical development and need the proof of concept in human beings. GERD is one of the most frequent diagnoses in clinical practice with increasing prevalence worldwide. Recognizing the historical evolution of GERD management can help care providers to better understand therapeutic options for their patients, as well as focus on unmet needs that deserve further attention. PPIs are still the first choice for GERD or NERD patients, with good evidence in favour of their efficacy, despite some concerns about safety. As with any medical intervention, it is recommended to prescribe PPIs for patients with clear indication, using adequate dosing and monitoring for adverse events.

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About the Author:

Dr. Ajay Kumar Singh, M.Sc. (Gold Medalist), Ph.D. is the author and founder of “Pharma Solutions by Dr. Ajay”.

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