unit-4 antacids.pptx

Antacids are weak bases given orally to neutralize the gastric acid and raise the gastric pH of gastric contents. They also inhibit pepsin formation.

1. PRESENTED BY : VKSK PRIYANKA KAVULURU M.Sc. N ( OBSTETRICS & GYNAECOLOGICAL NURSING) CLINICAL INSTRUCTOR , SMVDCoN UNIT-IV DRUGS ACTING ON GI SYSTEM ANTACIDS ALLPPT.com _ Free PowerPoint Templates, Diagrams and Charts

2. DEFINITION Antacids  are medicines that neutralize stomach  acid. Or Antacids are weak bases given orally to neutralize the gastric acid and raise the gastric pH of gastric contents. They also inhibit pepsin formation. Or Antacids are weak basic salts, which neutralize gastric acid and raise gastric Ph.

3. INDICATIONS GERD Acid ingestion Peptic ulcer disease Gastric hyperacidity. Peptic ulcer. Gastritis. Reflex oesophagitis. Chronic renal failure (uremia).

4. CONTRAINDICATIONS chronic heart failure Hemorrhoids Impacted stool Stomach or intestine blockage Incomplete or infrequent bowel movements Kidney disease, serious kidney problems Aluminium poisoning Chronic diarrhea Hypophosphatemia Hypernatremia ’

5. CLASSIFICATION SYSTEMIC ANTACIDS NONSYSTEMIC ANTACIDS

6. SYSTEMIC ANTACIDS Sodium bicarbonate is absorbed and may cause alkalosis; hence it is called “systemic antacid”. Higly water soluble and rapidly absorbed in gut. Rapidly neutralizes acid in the stomach and Act only for shorter duration. Systemically they these drugs act for longer duration therefore they may cause metabolic alkalosis.

7. Systemic antacids contd … Sodium bicarbonate (NaHCO3 ) This is still widely used by the lay people as it produces prompt relief from heart burn and dyspepsia . M.O.A: it is a powerful and rapid acid neutralizer and also used to alkalize urine and to treat acidosis. Dose : 1gm of sodium bicarbonate neutralizes 12 Meq Hcl . * Advantages: a- it is immediately effective in neutralizing the HCL in the stomach because of its high water solubility. b- Duration of action is short. * Disadvantages: a- rapid liberation of CO2 may lead to gastric distention, perforation of ulcer, and belching. b- acid rebound. c- metabolic alkalosis and disturbance of acid-base balance.

8. Sodium citrate / sodium acetate It is having similar properties to sodium bicarbonate it does not produce carbondioxide 1gm neutralizes 10 Meq of Hcl Systemic antacids contd …

9. NONSYSTEMIC ANTACIDS These are insoluble and largely unabsorbable basic agents and neutralizes acid in the stomach. The base may be hydroxide or carbonate or trisilicate combined with cation such as Mg++, Al +++ or Ca++. During neutralization of the acid the cation e.g. Mg++ forms a chloride. In the alkaline ph of small intestine, the chloride salt reacts with the bicarbonate from the intestinal juices to regenerate the original salt. Hence systemic alkalosis is avoided.

10. Non Systemic antacids classification: According to their capacity to increase gastric PH, they can be sub classified into: Buffer antacids: ex.: Aluminium hydroxide gel [Al(OH)3]. They limit the rise of gastric PH below neutrality. Non-buffer antacids (Alkali antacid): ex.: Calcium carbonate [CaCO3], Magnesium oxide [ MgO ], Magnesium carbonate [MgCO3], Magnesium hydroxide [Mg(OH)2]. They potentially permit an elevation in PH above neutrality. Miscellaneous antacids: ex.: Sodium carboxymethyle cellulose.

11. Advantages general The non-systemic antacids are used either alone or in combination with each other. They neutralize gastric, but not tend to cause systemic alkalosis because they are insoluble basic compound and hence poorly absorbed, so they don’t disturb acid-base balance in case of peptic ulcer, these drugs are preferred.

12. Aluminium hydroxide gel [Al(OH)3] This drug is a good adsorbent and adsorbs toxins, gases, and bacteria M.O.A : this is avilable either as a white colloidal, viscous suspension or as dried gel in the form of powder or tablets. It reacts with gastric acid to form aluminium chloride. DOSE: ( i ) aluminium hydroxide gel 4-8ml evry 2-4hrs (ii) aluminium hydroxide 0.5gm tablets; 1-2 tablets to be chewed q.i.d . DISADVANTAGES: Constipation which can be prevented by mixing of aluminium salts with magnesium salts. Decreases phosphate absorption by forming insoluble aluminium phosphate in the intestine.

13. Aluminium phosphate gel It is sometimes preferred to aluminium hydroxide gel, as it does not interfere with phosphate absorption.

14. Magnesium oxide and Magnesium hydroxide: Magnesium oxide on contact with water is converted to magnesium hydroxide which combines with gastric acid. M.O.A : it is a quick acting antacid with prolonged action. In small intestine mg(oh)2 is regenerated and excreted in the feces. DOSE: milk of magnesia as a antacid 4ml; as a laxative 15ml. DISADVANTAGES: Normally about 20% magnesium is absorbed which is rapidly excreted through kidney. However renal dysfunction or repeated dose can result in dangerous degree of retention.

15. Magnesium trisilicate: It is a fine, white, tasteless powder, insoluble in water. M.O.A : in stomach it reacts with acid to form hydrated silicon dioxide. As it becomes gelatinous in consistency , it provides a protective coating to the ulcer crater. One gram of magnesium trisilicate neutralises about 9-11meq of gastric acid. DOSE: 2-4g every 1-4h. The tablet should be chewed before it is swallowed. The drug can also be used in powder form. ADR: MILD DIARRHEA, a small amount of magnesium absorbed may produce CNS depression in the presence of impaired renal function .

16. Magnesium carbonate: This antacid has properties similar to those oif mag nesium hydroxide except that carbon dioxide is liberated during neutralisation of the acid. One gram neutralizes 20 Meq of acid.

17. Calcium carbonate: it occurs as a white powder with a chalky taste. M.O.A: In stomach it reacts with gastric acid to form Calcium chloride. It acts quickly as it has high neutralizing capacity. One gram neutralizes 21meq of the acid. Its action is prolonged and it is inexpensive. Dose: powdered preipitated chalk or tablet conatining 1gm of calcium carbonate. 2-4gm. Disadvantages: Gastric acid rebound Hyperglycemia Calciuria Metastatic calcification and urolithiasis Hypophosphatemia Constipation

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