SODIUM BICARBONATE

Sodium bicarbonate injection, USP is a sterile, nonpyrogenic, hypertonic solution of sodium bicarbonate (NaHCO 3 ) in water for injection for administration by the intravenous route as an electrolyte replenisher and systemic alkalizer. Solution is offered in concentration of 8.4%. See table in HOW SUPPLIED section for contents and characteristics. The solution contains no bacteriostat, antimicrobial agent or added buffer and are intended only for use as a single-dose injection, the approximate pH of the solution is between 7.0 to 8.5. When smaller doses are required, the unused portion should be discarded. Sodium bicarbonate USP, 84 mg is equal to one milliequivalent each of Na + and HCO 3 - . Sodium bicarbonate, USP is chemically designated NaHCO 3 , a white crystalline powder soluble in water and insoluble in ethanol. Water for injection, USP is chemically designated H 2 O.

Sodium bicarbonate injection is indicated in the treatment of metabolic acidosis which may occur in severe renal disease, uncontrolled diabetes, circulatory insufficiency due to shock or severe dehydration, extracorporeal circulation of blood, cardiac arrest and severe primary lactic acidosis. Sodium bicarbonate is further indicated in the treatment of certain drug intoxications, including barbiturates (where dissociation of the barbiturate-protein complex is desired), in poisoning by salicylates or methyl alcohol and in hemolytic reactions requiring alkalinization of the urine to diminish nephrotoxicity of hemoglobin and its breakdown products. Sodium bicarbonate also is indicated in severe diarrhea which is often accompanied by a significant loss of bicarbonate. Treatment of metabolic acidosis should, if possible, be superimposed on measures designed to control the basic cause of the acidosis - e.g., insulin in uncomplicated diabetes, blood volume restoration in shock. But since an appreciable time interval may elapse before all of the ancillary effects are brought about, bicarbonate therapy is indicated to minimize risks inherent to the acidosis itself. Vigorous bicarbonate therapy is required in any form of metabolic acidosis where a rapid increase in plasma total CO 2 content is crucial - e.g., cardiac arrest, circulatory insufficiency due to shock or severe dehydration, and in severe primary lactic acidosis or severe diabetic acidosis.

Sodium bicarbonate injection is administered by the intravenous route. In cardiac arrest, a rapid intravenous dose of one to two 50 mL vials (44.6 mEq to 100 mEq) may be given initially and continued at a rate of 50 mL (44.6 mEq to 50 mEq) every 5 minutes to 10 minutes if necessary (as indicated by arterial pH and blood gas monitoring) to reverse the acidosis. Caution should be observed in emergencies where very rapid infusion of large quantities of bicarbonate is indicated. Bicarbonate solutions are hypertonic and may produce an undesirable rise in plasma sodium concentration in the process of correcting the metabolic acidosis. In cardiac arrest, however, the risks from acidosis exceed those of hypernatremia. In less urgent forms of metabolic acidosis, Sodium bicarbonate injection may be added to other intravenous fluids. The amount of bicarbonate to be given to older children and adults over a four-to-eight-hour period is approximately 2 mEq/kg to 5 mEq/kg of body weight - depending upon the severity of the acidosis as judged by the lowering of total CO 2 content, blood pH and clinical condition of the patient. In metabolic acidosis associated with shock, therapy should be monitored by measuring blood gases, plasma osmolarity, arterial blood lactate, hemodynamics and cardiac rhythm. Bicarbonate therapy should always be planned in a stepwise fashion since the degree of response from a given dose is not precisely predictable. Initially an infusion of 2 mEq/kg to 5 mEq/kg body weight over a period of 4 hours to 8 hours will produce a measurable improvement in the abnormal acid-base status of the blood. The next step of therapy is dependent upon the clinical response of the patient. If severe symptoms have abated, then the frequency of administration and the size of the dose may be reduced. In general, it is unwise to attempt full correction of a low total CO 2 content during the first 24 hours of therapy, since this may be accompanied by an unrecognized alkalosis because of a delay in the readjustment of ventilation to normal. Owing to this lag, the achievement of total CO 2 content of about 20 mEq/liter at the end of the first day of therapy will usually be associated with a normal blood pH. Further modification of the acidosis to completely normal values usually occurs in the presence of normal kidney function when and if the cause of the acidosis can be controlled. Values for total CO 2 which are brought to normal or above normal within the first day of therapy are very likely to be associated with grossly alkaline values for blood pH, with ensuing undesired side effects. Parenteral drug products should be inspected visually for particulate matter and discoloration prior to administration, whenever solution and container permit. See PRECAUTIONS .

Sodium bicarbonate injection is contraindicated in patients who are losing chloride by vomiting or from continuous gastrointestinal suction, and in patients receiving diuretics known to produce a hypochloremic alkalosis.

Overly aggressive therapy with sodium bicarbonate injection can result in metabolic alkalosis (associated with muscular twitchings, irritability and tetany) and hypernatremia. Inadvertent extravasation of intravenously administered hypertonic solutions of sodium bicarbonate have been reported to cause chemical cellulitis because of their alkalinity, with tissue necrosis, ulceration or sloughing at the site of infiltration. Prompt elevation of the part, warmth and local injection of lidocaine or hyaluronidase are recommended to reduce the likelihood of tissue sloughing from extravasated intravenous (I.V.) solutions.

Laboratory Tests The aim of all bicarbonate therapy is to produce a substantial correction of the low total CO 2 content and blood pH, but the risks of overdosage and alkalosis should be avoided. Hence, repeated fractional doses and periodic monitoring by appropriate laboratory tests are recommended to minimize the possibility of overdosage.