Fifteen different isolates of Pseudomonas aeruginosa were used to study the kinetics of adhesion to 304 and 316-L stainless steel. Stainless steel plates were incubated with approximately 1.5 x 107 CFU/ml in 0.01 M phosphate-buffered saline (pH 7.4). After the plates were rinsed with the buffer, the number of adhering bacteria was determined by a bioluminescence assay. Measurable adhesion, even to the electropolished surfaces, occurred within 30 s. Bacterial cell surface hydrophobicity, as determined by the bacterial adherence to hydrocarbons test and the contact angle measurement test, was the major parameter influencing the adhesion rate constant for the first 30 min of adhesion. A parabolic relationship between the CAM values and the logarithm of the adhesion rate constants (In k) was established. No correlation between either the salt aggregation or the improved salt aggregation values and the bacterial adhesion rate constants could be found. Since there was no significant correlation between the bacterial electrophoretic mobilities and the In k values, the bacterial cell surface charge seemed of minor importance in the process of adhesion of P. aeruginosa to 304 and 316-L stainless steel.

The sorption of nitroglycerin, from 5% glucose solution, by infusion sets was investigated under simulated perfusion conditions. Several burettes, sets and catheters were evaluated. The stability of the drug in the presence of glucose was also determined. High density polyethylene and glass proved satisfactory for its perfusion in solutions. A method for the evaluation of its uptake under simulated perfusion conditions is described.

The crystalline structure of two different batches of chloroquine diphosphate was studied. Differential thermal analysis showed the existence of two polymorphic modifications in one of the batches, whilst spectral analysis did not reveal any differences. This discrepancy is attributed to the fact that the second modification is formed during the transition phase when analysed by differential thermal analysis. This recrystallization process is initiated by the presence of seed material. The ratio of transition heat of both modifications is dependent on particle size and heating rate during analysis.

In this study Betnelan-V@ cream was diluted with Beeler's basis and Cold cream@. Cold Cream@ reduced the skin-blanching activity of the original cream more than Beeler's base. T h e stability of betamethasone-17-valerate was better in a Beeler's basis dilution than in a Cold cream@ dilution. I N T R O D U C T I O NAlthough the extemporaneous dilution of creams may lead to problems such as drug degradation or non-homogeneity, physicians still prescribe diluted corticosteroid topical preparations in order to obtain a less potent preparation (1,2). Since the release and the chemical stability of corticosteroid topical preparations depend on the vehicle, dilution with bases different from those used by the manufacturer may lead to instability (3-5).Bases such as Emulsifying ointment BP and Plastibase were unsuitable as diluents for Betnovatea ointment due to rearrangement to betarnethasone-21-valerate and hydrolysis to betamethasone (Mi). Unguentum Merck@ and white soft paraffin produced stable dilutions but the potency was equivalent to the undiluted ointment (6,9-10). However, when the new formulation of Betnovatea ointment was diluted with white soft paraffin, the potency was reduced to the same extent as the proprietary diluted ointment. This difference in potency of the extemporaneously diluted products clearly shows the effect of vehicle composition on the release of betamethasone-17-valerate (1 1-12). Betnovatem cream diluted in several cream bases shows good stability and the potency of the dilutions was equivalent to the undiluted cream (13)(14).Since dilutions do not always produce a less potent preparation, the aim of the study was to verify the stability and the clinical effectiveness of Betnelan-V@ cream diluted with Beeler's basis and Cold cream@ containing 5 O , w/w urea. The skin blanching test was used to assess the clinical effectiveness of the dilution. This test is a precise and reproducible method for predicting the topical effect of corticosteroids when carried out under standard conditions (15)(16)(17)(18).

Petrolatums from different manufacturers were characterized by viscosity measurements, oil number and ratio of low to high mol. wt components (capillary gas chromatography). Viscosity measurements and oil numbers of original materials did not correlate with the viscosity of the processed material in eye ointments. The ratio of high carbon number components to the low carbon number components was a reliable predictor for the viscosity of the formulation.