

An Overview of Antacids
When the extra secretion of acid takes place in the stomach, it causes on-off pain, bloating sensation, low appetite and many other health-related problems. Overproduction of acids can even lead to critical diseases like the formation of stomach ulcers. So, how to control the acids?
Antacids are prescribed to people who suffer from acidity problems. In the year 1970, acidity treatment was started using antacids. In the following content, you will get more familiar with: what are antacids, what do antacids do, antacid medicines, etc.
What is Antacid Medicine?
The category of medicines that neutralizes stomach acids are known as antacids. These tablets contain certain ingredients like calcium, sodium bicarbonate, aluminium and magnesium which act like alkalis or bases to oppose acid in the stomach and make pH neutral.
pH refers to the evaluation of hydrogen ion concentration in any solution, and it shows how alkaline or acidic those solutions are. The pH scale has a lower limit of one and an upper limit of 14. If the pH of a solution is seven, it is neutral, if more than seven it is alkaline and less than seven is acidic. Typically, the pH of gastric acid is between the range of 1.5 and 3.5.
The Following Table depicts the Commonly used Antacids
Now that you have understood what an antacid tablet is, let us move further with antacid components.
Components of Antacid Medicines
Sodium Bicarbonate
NaHCO₃: It is a short-acting and weak antacid. Though it u's a harmless household remedy, the content of sodium present in it is disadvantageous. Doctors generally do not recommend "baking soda" or "bicarb", but it is a commonly used ingredient of several patent medicines. Bicarbonate holds an effervescent trait that illustrates the commercial existence of pain-killer/antacid blends like Bromo-SeltzerTM and Alka-SeltzerTM. This component reacts with hydrochloric acid (HCl) of the stomach to yield carbon dioxide (CO2) that gets absorbed fast but occasionally evokes a satisfying burp.
Systemic alkalosis (imbalance of the human body's pH level) may be a result of bicarbonate overuse. People, who have high blood pressure and are prescribed not to have much sodium, should avoid bicarbonate.
Magnesium Hydroxide
Mg(OH)2 : It is popularly called as milk of magnesia. Similar to magnesium sulphate and magnesium citrate, magnesium hydroxide is also a good laxative. Manufacturers mix this component with the aluminium hydroxide to control the diarrhoea effect it causes. However, the price of medicine increases and aluminium hydroxide decreases the benefit of antacid.
Magnesium hydroxide itself does not get absorbed in the intestine. Instead, when it interacts with the stomach acid; it releases magnesium chloride which is absorbed. Mg (magnesium) holds a lot of functions in cells of the human body. However, it has a harmful effect if levels of Mg increase in blood. Also, people with renal failure must avoid magnesium.
Aluminium Hydroxide
Al(OH)3: In comparison to the previous component, this one is weak and has slow action on the human body. Moreover, neutralizing power varies among commercial medicines.
Aluminium may safeguard the lining of the stomach from the harmful effects of irritants like alcohol. Al(OH)3 has other applications as well. It helps in binding phosphate in gut lumen to yield insoluble aluminium phosphate. This product is useful for kidney failure when serum phosphate goes high abnormally and for people who tend to form kidney stones that contain phosphate.
Prolonged use of this component may cause brain damage, metabolic bone conditions like osteoporosis and osteomalacia, and risk of causing fractures, particularly in malnourished people.
Calcium Carbonate
CaCO3 : Chalk is the common name for calcium carbonate and is the most abundantly available antacid. It can neutralize acid entirely in the stomach. However, it may not be the right choice for daily use.
One major side effect of antacids is that gastric acid secretion may rebound after taking this medicine. Commercial antacid tablets that contain calcium have Titralac TM and TumsTM, and their dosage should not go above 3 g each day.
Besides the primary components, there are some extra components, such as:
Peppermint flavouring
Antiflatulent
Alginic acid
How do Antacids work?
All antacid tablets can work in two manners.
Antacids cover the esophagus surface with a preventive layer against acids of the stomach.
They release a gel on the surface of the stomach that helps to stop the leakage of acid to the food pipe. This way, it can prevent heartburn symptoms.
Next, let us discuss what are antacids used for?
Use of Antacids
Apart from heartburn, the primary uses of antacids are to provide relief from Gastroesophageal Reflux Disease (GERD), indigestion or dyspepsia, belching, bloating, and feeling of discomfort in the gut or stomach. By counteracting stomach acids, these medicines can help to cure the feeling of burning in the throat or chest due to acid reflux, bitter taste in the mouth, a sensation of pain while lying down, regurgitation and continuing dry cough. These acid medicines can be merged with other tablets well to provide relief from heartburn symptoms.
What is GERD and Acid Reflux?
Acid reflux takes place when stomach contents reach up in the oesophagus. It is also termed gastroesophageal reflux or acid regurgitation. If you experience acid reflux symptoms more than two times a week, you may be suffering from GERD.
Moreover, GERD can sometimes lead to difficulty in swallowing food and also breathing conditions like asthma.
Did You know?
The National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) suggest that 20% of US citizens are affected with GERD, and if it is not treated, can cause serious issues.
When a person is diagnosed with GERD, medical practitioners usually advise making changes in eating habits and lifestyle. Besides antacids, doctors also prescribe two different classes of medicines like H2 receptor blockers and proton pump inhibitors.
Some Widely used H2 Receptor Blockers are:
Nizatidine (Axid)
Cimetidine (Tagamet HB and Tagamet)
Famotidine (Pepcid AC and Pepcid)
Note: The selling of Tagamet across the world was most massive until ranitidine (Zantac) was introduced.
Some Commonly used Proton Pump Inhibitors are:
Lansoprazole (Prevacid 24 HR)
Omeprazole (Prilosec)
Pantoprazole sodium (Protonix)
Rabeprazole sodium (Aciphex)
Other Than the Earlier mentioned Disorders, a Few Antacids can help to cure unrelated Health Problems Like:
Deficiency of calcium.
High blood phosphate levels.
Formation of stones in the kidney.
Deficiency of magnesium.
By now, you must have got familiar with the use of antacids. However, you must keep in mind that all medicines come with side effects. The following section is related to the side effects of antacids.
Antacids Side Effects
The ingredients present in antacid tablets are responsible for the unwanted side effects. However, few product combinations show side effects that invalidate each other. For example, magnesium can cause diarrhea and aluminium can cause constipation, so a tablet containing these two components has a more neutral effect on the bowel.
Generally, if you take antacids as directed by a physician or the way mentioned on the tablet strip, you will experience comparatively fewer effects. Over usage of the medicines along with prolonged usage without prescription, they may have side effects.
Common Side Effects of Antacids
Constipation
Aluminium toxicity
Low levels of blood phosphate
Osteomalacia
Kidney stones
Nausea
Alkalosis
High magnesium level in blood
Increase in blood pressure, etc.
Furthermore, if high doses of antacids are taken for an extended period, it can cause a problem termed as an acid rebound. This condition occurs when the stomach releases more acids after the consumption of drinks and food.
Sometimes people take medicines for acidity issues on their own. However, you must always take drugs after consultation with a doctor as only they will understand which is the antacid medicine that can cure your problem.
Precautions
Most people are not adversely affected by antacids. People with specific medical issues, on the other hand, should see their doctors before using antacids containing aluminium hydroxide and magnesium carbonate. People with heart failure, for example, may be subjected to sodium limitations to reduce fluid accumulation. However, antacids are frequently high in salt. Before using antacids, these persons should consult with their doctor. After using antacids, those with kidney failure may experience an aluminium accumulation. Aluminium poisoning may result as a result of this. Electrolyte balance issues are common in people with renal failure. All antacids include electrolytes, which may exacerbate electrolyte balance issues. Before giving your child antacids, consult with their doctor. Because children seldom have symptoms of high stomach acid, their symptoms might be due to another issue.
How and When to take Antacids
Check the package or leaflet for directions on how much and how often to take the antacid. This depends on the medication you're taking. Antacids should be taken when you have symptoms or suspect you may have them soon - for most people, the ideal time to take them is with or shortly after meals, and immediately before going to bed. Keep in mind that children's dosages may be lower than those of adults. Antacids should be taken with meals or shortly after eating because this is when you are most likely to experience indigestion or heartburn. If taken with meals, the medicine's impact may last longer. Antacids can affect the effectiveness of other medications, so avoid taking them within 2 to 4 hours of having an antacid.
Hyperacidity
To improve digestion, the stomach secretes Hydrochloric Acid, a digestive liquid that breaks down food particles into their simplest form. Hyperacidity is a condition that occurs when there is an excess of hydrochloric acid in the stomach. Our stomach consists of acid or HCL- Hydrochloric acid, the amount of acid in our stomach is pH 4. This means that there is a highly acidic environment within, which is also required for humans because any germs that reach our stomach, die in the acidic environment, therefore acidity is important. However, in certain circumstances, this acidic nature exceeds the required amount, and the acidity begins to pain. Following are some of the signs and symptoms of Hyperacidity:
Heart & chest burn
Throat burn
A constant sour taste in your mouth or bitter-tasting acid backing up into your throat and tongue.
Chest pain.
Dry Cough
Asthma
Chronic Sinusitis
Ear pain
Hyperacidity Cure
Avoid meals that are very salty, fatty, sour, or spicy. Maintain a balanced, healthful diet.
It is also essential to exercise for at least half an hour since it promotes digestion and bowel motility, hence reducing hyperacidity. Walking is the greatest option.
Workouts that stimulate the abdominal muscles, such as crunches, should be avoided.
Heavy lifting should be avoided by people who have hyperacidity.
Treatment of Acidity with the use of Histamine
Histamine is a significant advancement in the treatment of hyperacidity. In the stomach, histamine acts as a stimulant for the release of pepsin and hydrochloric acid. Cimetidine is a medication that works by limiting the effects of histamine. It inhibited the interaction between histamine and receptors, resulting in a reduction in acid release.
Do It Yourself
1. What is the other name for magnesium hydroxide?
a) sugar b) milk of magnesia c) chalk d) baking soda
2. Is the following sentence true or false?
Osteoporosis is a side effect of antacids.
3. Classify the following medicines like antacids, proton pump inhibitors and H2 receptor blockers.
a) Sodium bicarbonate b) Nizatidine c) Aluminium hydroxide d) Omeprazole
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FAQs on Antacids
1. What are antacids as per the Class 12 Chemistry syllabus?
Antacids are chemical substances, typically weak bases, that are used to neutralise the excess hydrochloric acid (HCl) produced in the stomach. This action helps to raise the stomach's pH level, providing relief from symptoms like acidity, heartburn, and indigestion. They treat the symptom, not the underlying cause of acid overproduction.
2. What are some common chemical compounds used as examples of antacids?
According to the CBSE curriculum for 2025-26, common chemical compounds used as antacids include:
- Sodium Bicarbonate (NaHCO₃), also known as baking soda.
- Magnesium Hydroxide [Mg(OH)₂], often called milk of magnesia.
- Aluminium Hydroxide [Al(OH)₃].
- Calcium Carbonate (CaCO₃).
- Combinations of magnesium and aluminium salts are also very common.
3. How do antacids work to neutralise stomach acid?
Antacids work through a simple chemical process called neutralisation. Being weak bases, they react with the strong hydrochloric acid (HCl) in the stomach. This acid-base reaction produces a salt and water, which are neutral. For example, the reaction for magnesium hydroxide is: Mg(OH)₂ + 2HCl → MgCl₂ + 2H₂O. This chemical reaction effectively reduces the amount of acid, raising the stomach's pH and alleviating discomfort.
4. Why are modern antacids often a combination of magnesium and aluminium salts?
Modern antacids use a combination of magnesium and aluminium salts to balance out their side effects. Magnesium hydroxide [Mg(OH)₂] is an effective antacid but can have a laxative effect (cause diarrhoea). In contrast, aluminium hydroxide [Al(OH)₃] can have a constipating effect. By combining them in one formulation, manufacturers can create a product that neutralises acid effectively while minimising these gastrointestinal side effects.
5. What is the difference between an antacid and an antihistamine like Cimetidine for treating acidity?
The key difference lies in their mechanism of action. Antacids provide quick, short-term relief by directly neutralising the acid that is already present in the stomach. In contrast, drugs like Cimetidine (Tagamet) or Ranitidine are antihistamines. They work by blocking the histamine receptors in the stomach lining, which prevents the stimulation of cells that produce acid. Essentially, antacids treat the symptom, while antihistamines reduce the cause (acid production).
6. Is Eno considered an antacid and how is it different from a simple antacid tablet?
Yes, Eno is an antacid. It is different from a simple tablet because it is an effervescent preparation. Its main active ingredient is sodium bicarbonate (a base) mixed with an edible acid like citric acid. When dissolved in water, they react to produce carbon dioxide gas (the fizz), which helps relieve bloating. The sodium bicarbonate component then works to neutralise the excess stomach acid, providing fast relief.
7. Why is it not advisable to use sodium bicarbonate as a regular antacid?
While sodium bicarbonate (baking soda) is a fast-acting antacid, its regular use is not recommended. Being highly soluble, it can be absorbed into the bloodstream and make the body's overall pH alkaline, disturbing the acid-base balance. Furthermore, it can cause the stomach to produce even more acid in response, a phenomenon known as acid rebound, making the problem worse in the long run.
8. Can milk be used as an effective antacid?
Milk is not an effective long-term antacid. While it can provide very temporary relief because it is slightly alkaline, the calcium and proteins in milk can trigger the stomach to secrete more acid shortly after consumption. This can lead to a rebound effect, where the heartburn and acidity return, sometimes even worse than before. Therefore, it is generally not a recommended solution for managing acidity.

















