Antacid preparations

This electrolyte plays a vital role in the acid-base balance of the body. Bicarbonate may be given IV as sodium bicarbonate (NaHC03) in the treatment of metabolic acidosis, a state of imbalance that may be seen in diseases or situations such as severe shock, diabetic acidosis, severe diarrhea, extracorporeal circulation of blood, severe renal disease, and cardiac arrest. Oral sodium bicarbonate is used as a gastric and urinary alkalinizer. It may be used as a single drug or may be found as one of the ingredients in some antacid preparations. It is also useful in treating severe diarrhea accompanied by bicarbonate loss. 

There are problems as well in the absorption of certain drugs in the presence of specific food components. L-Dopa absorption may be inhibited in the presence of certain amino acids formed from the digestion of proteins [43], The absorption of tetracycline is reduced by calcium salts present in dairy foods and by several other cations, including magnesium and aluminum [115-117], which are often present in antacid preparations. In addition, iron and zinc have been shown to reduce tetracycline absorption [118], Figure 17 illustrates several of these interactions. These cations react with tetracycline to form a water-in-soluble and nonabsorbable complex. Obviously, these offending materials should not be co-administered with tetracycline antibiotics. 

Q22 Alg inic acid is found in some antacid preparations. The primary function is to ... 

Acid neutralizing capacity (ANC) - ANC is a consideration in selecting an antacid. It varies for commercial antacid preparations and is expressed as mEq/mL. Milliequivalents of ANC is defined by the mEq of hydrochloride required to keep an antacid suspension at pH 3.5 for 10 minutes in vitro. An antacid must neutralize at least 5 mEq/dose. Also, any ingredient must contribute at least 25% of the total ANC of a given product to be considered an antacid. 

Antacids are basic compounds that neutralise acid in gastric lumen, have no effect on gastric acid secretion. They are quantitatively compared in terms of their acid neutralizing capacity (ANC), which is defined as the quantity of 1 N HCl (in MEq) that can be brought to pH 3.5 in 15 minutes by a unit dose of antacid preparation. An ideal antacid should be potent in neutralizing acid, inexpensive, not absorbed from GIT and contain negligible amounts of sodium, should be sufficiently palatable to be readily tolerated with repeated dosage and should be free of side effects. An ideal antacid is yet to be developed. 

Five principal active ingredients are used in antacid preparations (1) Sodium bicarbonate isa rapid and effective neutralizer. The compound does yield large amounts of absorbable sodium, undesirable in some... 

Antacid preparations based on aluminium hydroxide sometimes contain magnesium salts (and carbonate or oxide) to offset the constipating effect of the alumina. This laxative effect of salts such as magnesium sulphate (or citrate) and other saline cathartics such as potassium sodium tartrate is due to their incomplete absorption from the digestive tract so that, by osmotic forces, they retain water in the intestinal lumen. 

Fairweather-Tait S, Hickson K, McGaw B, et al. 1994. Orange juice enhances aluminum absorption from antacid preparation. Eur J Clin Nutr 48 71 -73. 

Recent concern relative to the high incidence of osteoporosis in elderly, female, Americans has resulted in increased usage of calcium supplements. Calcium carbonate contains more calcium per weight unit of the salt than does calcium phosphate, calcium lactate or calcium gluconate hence, either calcium carbonate or one of the calcium carbonate forms such as oyster shells or dolomite is most often the calcium salt choice for use in a supplement since fewer capsules need to be taken Z). Since calcium carbonate preparations marketed as antacids are often sold at a price lower than are those calcium carbonate preparations marketed as calcium supplements, calcium antacid preparations are currently being used as calcium supplements. 

Q12 Pharmacological treatment of peptic ulcers aims to restore the balance between mucosal defence and mucosal damage by acid and pepsin in the stomach wall. The general mechanisms of drug action include (i) inhibition of acid secretion, (ii) neutralization of the acid with antacid preparations, (iii) eradication of H. pylori with antibiotics and (iv) enhancement of the mechanisms which protect the mucosa. 

Aucamp and Meyer (131) reported that well- Controlled epileptics may experience sudden exacerbation of their seizures If they begin taking drugs with anticholinergic activity (as In some antacid preparations) or antlhlstamlnlc activity (as In preparations for amelioration of colds and Influenza). 

Among effervescent antacid preparations, Alka-Seltzer, an effervescent antacid analgesic product, has been available since the 1930s. Pure effervescent antacid products are marketed in many countries. 

The aluminum hydroxide gel exhibits thixotropic behavior. In addition, gel stability is enhanced by polyols such as mannitol and sorbitol. However, unlike other gels, aluminum hydroxide gels do not have demulcent properties they are used mainly as an oral antacid preparations. 

In pharmaceutical applications, neohesperidin dihydrochalcone is useful in masking the unpleasant bitter taste of a number of drugs such as antacids, antibiotics, and vitamins. In antacid preparations levels of 10-30 ppm result in improved palat-ability. 

Bismuth-containing antacid preparations have been in use for a long time, but some of the bismuth chelates (e.g. tripotassium dicitratobismuthate) are of proven benefit in ulcer, and, though it is not clear how they work, there is some... 

Demulcents are agents or preparations that protect the mucous membranes and relieve pain and irritation. They are thought to work by forming a protective film and are commonly incorporated into antacid preparations for protecting the gastric mucosa of the mouth. The most commonly used is alginic add or one of its alginate salts. 

LAXATIVE properties. It is used orally for the relief of hyperacidity, dyspepsia and indigestion, and as an adjunct in the treatment of peptic ulcers. It is a component of many compound antacid preparations, eg Algicon , Aludrox , Asilone , Dijex , Gastrocote , Gaviscon , Kolanticon , Maalox and Maclean . 

These are useful for patients that do not like to swallow tablets whole. They can be chewed and broken down in the mouth before swallowing. Commonly they are sweetened and flavoured to improve their palatability. Common examples include antacid preparations, where the relatively large tablets are still more convenient than the equivalent liquid preparation. 

Antacid preparations containing sodium bicarbonate should be avoided by patients on lithium therapy. Sodium ions are preferentially reabsorbed in the kidney, increasing lithium excretion and reducing plasma lithium concentrations. 

Tablet formulations account for about 45% of the formulations marketed in the UK with capsules accounting for about 15%. These formulations have the advantage of providing the dose in a discrete unit form that is stable, easily produced and transported and above all easily administered. The tablet is favoured because it is marginally cheaper to produce and slightly more stable under in-use conditions. The simplest solid dosage form is the drug powder itself, a presentation mode that is still used for some antacid preparations. For modem drugs the dose required is too small to be measured accurately by the patient and must therefore be presented preformed.

Aluminium is poorly absorbed from the GI tract, which is just as well since antacid preparations used by dyspeptic patients may contain as much as 500 mg of aluminium per tablet. Aluminium levels in water supplies are variable and may contain from less than 50 to more than I0(K) jg/l. This is a potential hazard to renal dialysis patients when the aluminium can enter the body across the dialysis membrane, thus bypassing intestinal absoiption. The water used in dialysis is now treated to remove contaminating metals. Acute aluminium toxicity is extremely rare. Aluminium toxicity in patients with renal dysfunc-... 

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