Effervescent formulation

Uses. Aspirin has analgesic, antiinflammatory, and antipyretic activity. It is used for the reHef of less severe types of pain, such as headache, neuritis, acute and chronic rheumatoid arthritis, and toothache. Aspirin can be purchased in a variety of OTC and prescription dosage forms made and formulated by many companies. Tablets, ie, buffered, plain, or enteric-coated, are the most familiar in the United States, but other forms such as powder and effervescent formulations are of considerable importance in other parts of the world. 

Medical Uses. Citric acid and citrate salts are used to buffer a wide range of pharmaceuticals at their optimum pH for stabiUty and effectiveness (65—74). Effervescent formulations use citric acid and bicarbonate to provide rapid dissolution of active ingredients and improve palatabiUty. Citrates are used to chelate trace metal ions, preventing degradation of ingredients. Citrates are used to prevent the coagulation of both human and animal blood in plasma and blood fractionation. Calcium and ferric ammonium citrates are used in mineral supplements. 

Tablet disruption following production of carbon dioxide is another mechanism used to enhance disintegration. This uses a mixture of sodium bicarbonate and a weak acid such as citric acid or tartaric acid and is exploited for effervescent formulations.

Essentially, effervescent formulations are produced in the same way as conventional tablets, although due to the hygroscopicity and potential onset of the effervescence... 

The absorption of the effervescent formulation of paracetamol was compared with that of a plain tablet in normal volunteers. As to the rate of absorption, this was more rapid and consistent from the effervescent preparation than from the plain tablet. This may have important therapeutic implications where a rapid and predictable analgesic effect may be desired. ... 

The acid and carbonate parts of the effervescent formulation can be granulated either separately or as a mixture with water (crystal water of citric acid, liquid water, or water vapor), ethanol (possibly diluted with water), isopropanol, or other solvents. 

Twenty lubricants for effervescent tablets were tested for lubrication efficiency in direct compression of a standard effervescent formulation. The lubricant concentration was high as compared to traditional tablet lubricants. By increasing the lubricant concentration... 

Chloroquine has a bitter taste, which can deter children from taking it, so a sweet effervescent formulation of chloroquine phosphate has been compared with chloroquine tablets in a pharmacodynamic study (37). However,... 

Sodium bicarbonate is metabolized to the sodium cation, which is eliminated from the body by renal excretion, and the bicarbonate anion, which becomes part of the body s bicarbonate store. Any carbon dioxide formed is eliminated via the lungs. Administration of excessive amounts of sodium bicarbonate may thus disturb the body s electrolyte balance, leading to metabolic alkalosis or possibly sodium overload with potentially serious consequences. The amount of sodium present in antacids and effervescent formulations has been sufficient to exacerbate chronic heart failure, especially in elderly patients. ... 

SMLR calibrations used up to four wavelengths and provided r values >0.99 and SEEs and SEPs <2.4%. Calibrations were developed using PLS on full- (1100 to 2500 nm) and reduced-wavelength (1300 to 1800 nm) ranges. Two or three factors were adequate for the calibrations, giving SEE and SEP values <2%. SMLR was more accurate for the simpler granule preparation, while PLS was more accurate for the effervescent formulation. 

Sodium dihydrogen phosphate and disodium dihydrogen pyrophosphate are acid salts that have been used in effervescent formulation. They are soluble in water, producing acid solution and react quickly with alkaline sources. They are commercially available either as granules or powder. 

Malic acid has recently been introduced in effervescent formulations because of its smooth and light taste. It is highly hygroscopic and soluble but has less acid strength than tartaric or citric adds. 

The use of a binder in effervescent formulations is limited by the fact that any binder, even if water soluble, will retard the tablet disintegration. Therefore, the amount of binder in a given formula will be a compromise between desired granule strength and desired disintegration time. 

Binders for dry granulation, such as lactose, mannitol, dextrose, are almost inappropriate, because they would be effective only in larger amount than that allowed by an effervescent formulations. The binder choice in wet granulation is also limited by the method of production and consequently by the amount of granulating liquid. 

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