In intravenous therapy the use of infusion fluids as vehicles or carriers for other parenteral drugs is now common. The extent of use of this drug administration method has been illustrated in many papers (1-8). A report from the early sixties shows that one or more drugs were added to about 10% of the infusion fluids administered (9). In the late sixties, however, the frequency of intravenous prescriptions containing additives had increased and figures of between 50 and 907; have been reported in several papers (2, 4, 5, 8). Reports over the last 5 years indicate that drugs are now less frequently administered as additives.The drugs added to infusion fluids are mainly antibiotics, electrolytes, heparin, vitamins and, to a lesser extent, several other drugs such as aminophylline and corticosteroids. Some of these drugs, for example, electrolytes, are available as sterile stock solutions designed for use as additives in infusion fluids. Usually, however, neither infusion fluids nor injections are formulated to be diluted or mixed with further drugs. The practice of adding drugs to large volume parenteral solutions may therefore result in incompatibility or stability problems.Several authors have reviewed the literature concerning addition of drugs to large volume solutions and provided references, tables and recommendations to reduce the occurrence of problems (10-16). There have been many studies on such incompatibilities; however, the literature in this area is often inconsistent and does not reflect clinically applicable situations. Several stated incompatibilities, reported in compatibility charts, are based on single observations. The influence of pH, the concentration of the drug and other factors have not been evaluated. Some are based only on the observation that no visible change has taken place in the admixture within a stated time.In some papers (6,17-27) the prediction ofcompatibility and stability ofdrugs added to infusion fluids was based on relevant physico-chemical principles. This more theoretical approach has allowed quantitative approximations to be made from kinetic data. Such a technique may be the best way to attack incompatibility problems. The success of this approach, however, depends on the available physicochemical information on the drug *Apoteksbolaget AB, (National Corporation of Swedish Pharmacies,) 105 14 Stockholm, Sweden. 29. Lebmnnn, H. (1959) uber pH-Werte von Infusionslosungen. dsterreichische Apotheker-Zeitung, 13, 30. Vogt. H. P Cklche, C. (1961) pH-Studien an den gebrauchlichsten Infusionslosungen, inbesondere die Ennittlung ihrer Pufferkapazitiit im Vergleich mit der des Blutes. Mitteilirngen der Deutschen Pharmaceutischen Gesellschaft. 31,97-107. 3 I . Cklche, G. (1966) Uber die Bedeutung de pH und Puferwertes von lnfusionslosungen fur Kombinationen mit weiteren Anneistoffen. Krankenhausact. 39.80-86. 32. hndgrm, P. P hndasj6, L. (1970) Studieson the stability and compatibility of drugs in infusion fluids. 1. pH and buffer capacity of infusion fluids. Acta Pharmacewica Sue...
