In case of severe alkalosis the body is depleted of water, H + , Cl – , and, to some extent, Na + . Ophthalmic buffers : The lachrymal fluid normally has a pH 7.4 with a range pH 5.0 to 8.3. The buffer capacity of pharmaceutical buffers used in ophthalmic (and parenteral) solutions should be low. The natural body buffers assimilate and bring medicinal solutions to the pH of body fluids. If buffers with high buffer capacity were used, they would resist change and interfere with the normal pH and buffer mechanisms of the body. Ophthalmic drugs often are amides and esters that undergo hydrolytic degradation. By buffering at an appropriate pH, their stability could be greatly increased. The actual formulation used in an ophthalmic solution is a compromise between stability, irritation, and absorption. Vehicle pH Salts of Boric acid 5.0 Procaine, phenylephrine, tetracaine, zinc Sorensen modified phosphate buffer 6.8 Atropine, ephedrine, eucatropine, scopolamine, homatropine, pilocarpine Examples of other clinical buffers : The adjustment of pH in or on the body may influence the therapeutic efficacy of a drug. The effectiveness of orally administered methenamine as an urinary antiseptic depends on the liberation of formaldehyde in acidic urine. The urine is adjusted to a pH 5 by the simultaneous administration of an acid-forming salt, e.g. ammonium chloride or sodium acid phosphate. Diluted sodium hypochlorite solution is used to irrigate wounds as a local antibacterial and to dissolve necrotic tissue. Adjustment of the solution to pH 9 with sodium bicarbonate minimizes the dissolving of blood clots while allowing the removal of unwanted debris.
Buffered ointments and lotions that maintain the normal acidity of the skin and facilitate healing are marketed e.g. "acid mantle" cream for diaper rash. Mercurous iodide ointments have greater antiseptic activity as the pH decreases to an optimum value of approximately pH of 4.
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- Fall '09
- pH, buffer solution