Interaction, arising between the drug and solvent injection solutions

For parenteral administration, in some cases it is necessary to dissolve drugs, produced as a lyophilized powder, such as antibiotics, or dilution of drugs, produced in ampoules, eg korglikona, noradrenaline hydrochloride (norepinephrine), By strophanthin and etc. For these purposes, the right choice is very important specialist solvent. Wrong choice of solvent can lead to inactivation of the drug substance or the formation of sludge in the case of its insufficient solubility.

As the solvent, most often recommend the use of water for injections, isotonic sodium chloride solution 0,9%, glucose solution or novocaine. Each has its advantages and disadvantages.

Water for injection most efficiently used to prepare solutions, administered in small volumes (5-15 ml). Administering to large quantities of aqueous solutions can lead to a change in the osmotic pressure of blood and erythrocyte hemolysis. The water for injection is dissolved ampicillin sodium salt, cardiac glycosides and other substances, which are sensitive to changes in pH of the medium and is easily inactivated, or react with solvents.

When administered to a large amount of the solution is usually used isotonic solution of sodium chloride and glucose by their selective recruitment. For Example, If dilute 2,5% ampoule solution etmozina isotonic sodium chloride solution, Opalescence is formed, and then the precipitate is fine (salting-out agent). Therefore etmozin (moracizin) must be diluted, using glucose.

But glucose solution is not always acceptable as solvent. Aqueous solutions of glucose in the presence of an alkali stable (accumulates due to the alkalinity of the glass), therefore it is stabilized solutions of hydrochloric acid to pH 3-4. When sterilization unregulated glucose solution takes its caramelization. For the same reason, it does not combine with substances, having an alkaline reaction (amidopirin, geksametilentetramin, aminofillin). In an alkaline environment glucose undergoes a series of transformations to form products, capable of interacting with each other, with water, oxygen in the air, as well as numerous medicinal substances.

Do not combine a glucose solution with a solution of ascorbic acid, which in its structure contains a highly reactive group is readily oxidized endiolnuyu. Ascorbic acid is oxidized to dehydroascorbic acid.

When dissolved in a solution of glucose antibiotics (benzilpenicillin, lincomycin, Erythromycin) the gradual destruction of their (slabokislaya environment); antibiotics with an aliphatic amino group (kanamycin and others.) form precipitates.

Cardiac glycosides (strophanthin and others.) a glucose solution for injection is subjected to acid hydrolysis with elimination of sugar residues, reducing their activity. Besides pharmaceutical incompatibility possible pharmacodynamic interaction. Therefore, it is advisable to cardiac glycosides dissolved in water for injection or isotonic sodium chloride solution.

Novocaine solution for injections hydrochloric acid to stabilize pH 3,8-4,5, that should be considered when dissolved therein a combination of drugs or solutions. For Example, when mixed with an aqueous solution of novocaine solution caffeine sodium benzoate or amidopirina, which have an alkaline reaction medium, neutralization reaction can occur, which leads to a change in stability and other properties of the drugs. In contrast to the above example, chlorpromazine aqueous solution has an acid reaction medium and dilution novocaine solution for injections their properties, as efficiency, preserves. Furthermore, sharing it with the introduction of novocaine advisable due to the decrease of painful and irritating properties.

Often antibiotics are used to dissolve 0.5-1% solution of novocaine. It should be taken into account, that the therapeutic efficacy of penicillin in this case did not immediately reduced, but gradually (through 30 m. inactivated 1-1,5%, through 24 o'clock - 30-40% antibiotic). Therefore, use only freshly prepared solutions of the antibiotic, and unencumbered solution is not subject to further use! Streptomycin is more stable in acidic medium, however, it is dissolved in a solution of novocaine. This solution can be stored for some time.

These examples demonstrate the importance of a professional approach to the selection of solvents based on their properties and physicochemical characteristics of the combined drugs. In the preparation of aqueous solutions for parenteral administration to consider the possible interaction between the components and the following general recommendations:

• solutions (mixtures thereof) Use only freshly prepared (immediately before administration);
• the more complex the structure of the dosage system, the greater the probability of interaction between the drug;
• should not be added to drugs Blood, plasma, amino acid solution, oil emulsions, as well as such unstable solutions, as mannitol and sodium bicarbonate (readily form a slurry when mixed with other drugs);
• amino acid solutions and fat emulsions can not enter a polyionic solution of glucose, since toxic products may be formed;
• glucose solutions (with a concentration of more 5%), used as solvents, can reduce the activity of many drugs;
• degradation of drugs (oxytocin, benzilpenicillin, Streptomycin, dikain, epinephrine, norepinephrine and others.) It can occur by reaction with ethanol and alkalis, which may remain in traces on sterile needles, Sprice, tools (during sterilization).