Inorganic Antacids

Inorganic Antacids - Antacids are basic or alkaline compounds used to neutralize excessive 
hydrochloric acid secreted in the stomach. Antacids increase the gastric Ph. towards neutrality. People who complain of acidity after taking a rich meal, fried or spicy food complain of epigastric distress or burning sensation in the stomach take antacids to relieve the symptoms of gastric acidity and, belching and bloating in the stomach.

Inorganic Antacids

Antacids are older drugs that have been  have been used for more than 100 years in medical practice in the treatment of acid related diseases of gastrointestinal tract. The use of sodium bicarbonate or baking soda as antacid is reported in literature for a pretty long time.

An ideal antacid needs to satisfy certain properties such as – it should produce quick onset of action, raise gastric ph. towards neutrality, it should not produce rebound acidity, it should not produce systemic alkalosis, it should not produce constipation.


The classification according to the digestive Absorption. Antacids are divided into 2 main categories which are very important in practice. These are mostly inorganic compounds or metallic salts marketed as antacids either alone or in combination. 

1. Absorbable: This includes carbonates, bicarbonates and oxides of sodium, magnesium and calcium

– sodium carbonate (baking soda);
– magnesium oxide (magnesia);
– magnesium carbonates;
– calcium carbonates;
– (sodium bicarbonates, sulphate, phosphate);
– calcium carbonates, magnesium carbonates, calcium carbonates, magnesium oxide).

2. non-absorbable: this includes phosphates, hydroxides and silicates of aluminium, magnesium

– aluminium phosphate;
– aluminium hydroxide;
– magnesium silicate;
– magnesium hydroxide;
– aluminium-magnesium combination;
– aluminium-magnesium combination with other active ingredients (anaesthetics,  antiflatulents, alginates, etc.).

Absorbable antacids react immediately with gastric hydrochloric acid to liberate carbon dioxide and water in the stomach. The liberation of carbon dioxide relieves the individual from belching or gastric distention and helps in the stimulation of gastric secretion. Sodium carbonate is a systemic antacid as is indicated in the classification mentioned above because it gets absorbed in the systemic circulation and exerts systemic effects, disturbs the blood ph. in whole and can lead to systemic alkalosis. However, non-systemic class of antacids are used in clinical practice. 

different from other antacids its systemic  effects, as it is absorbed into the blood and  affects the organism pH in whole.Such antacids come into  direct neutralization reaction with hydrochloric  acid in the stomach. They are characterized by  quick onset of therapeutic action and short-term effects, because after the administration of  absorbable antacids, the level of intragastric pH  increases up to 7 or more in a short period of  time (15-20 min) that stimulates secondary acid  hypersecretion (the «rebound» syndrome) 

[1, 4]. Nonabsorbable antacids start acting later (within  10-30 minutes), however, they have longer 
period of therapeutic action – nearly 2.5-3 hours. On the contrary absorbable or systemic antacids show fast on set of action but shorter duration of therapeutic effect. Among the antacids a very important parameter is buffer neutralising capacity which in case of  of nonabsorbable antacids is higher than that of the  absorbable antacids. 

Non-absorbable antacids 

have an important capability to absorb pepsin. This property of absorbing pepsin is much better than that of absorbable antacids. Pepsin also causes discomfort. So proteolytic activity of gastric acid gets reduced, which otherwise could have damaging properties in the gastric mucosa. How to evaluate efficiency of an antacid is million-dollar question. Its efficiency can be evaluated by is by acid neutralizing capacity (ANC). It is done by administering a standard dose of antacid, and getting the ph. raised to 3.5 during a predetermined time period usually 15 minutes. 
expressed in mEq of hydrochloric acid that is  neutralized by a standard dose of antacids  raising the pH to approximately 3.5 during a  predetermined time (usually – about 15  minutes). ANC is not the same among all antacids. It varies from antacid to antacid.  antacids possess high cytoprotective function 
and bind effectively bile acid. One of the most common adverse effect of antacids is that they cause constipation if continued for a long period because they slow down intestinal motility.

Aluminium containing antacids have been causing constipation much as compared to magnesium salt containing antacids which otherwise cause relaxation or slight laxative action. Therefore, it is justified to have a combination of aluminium containing salts and magnesium containing salts to minimize the adverse effect on motility. This very combination also provides rapid onset of therapeutic action. Here, ratio of aluminium to magnesium is very important when it is desired to have such a combination. administration of combined antacid  containing aluminium and magnesium  hydroxide provides more rapid onset of  therapeutic effect.

Sodium bicarbonate is widely used as antacid by people. It is effective in neutralising gastric acid ,the ph of which is normally 1 to 2.when complete neutralisation is effected ,pepsin becomes irreversibly inactivated, the stomach empties rapidly, and  rebound acid secretion takes place. If the ph. is maintained between 4


The above-mentioned inorganic antacids can simply neutralize the excess acid in the stomach. Such compounds do not control the actual source of acid secretion like proton pump inhibitors. They are used as add on therapy for the treatment of gastrointestinal disorders.

So far as medicinal or clinical indications of antacids are concerned antacids are prescribed in the treatment of acid disorders, such as gastrointestinal reflux disease, acid peptic disorders like peptic and duodenal ulcer, acute gastritis, Pain and dyspeptic syndromes, Cholecystitis, biliary dyskinesia.

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