p-55 IN VITRO STABILITY OF INTRAVENOUS AMINOPHYLLINE IN FAT CONTAINING TPN MIXTURES.

A.Andreu,D.Cardona,C.Pastor,J.M.Queralt~,J.Bonal.Pharmacy Service,Hospital S.Creu i S.Pau Barcelona,Haematology Services.Hospital Clinic Barcelona and Biochemistry Services Hospi- tal S. Creu i S. Pau Barcelona.

IV Aminophylline stability in fat containing TPN mixtures was tested with two di fferent dosages. One for smokers(0,9 mg/kg/h.) and other for car pulmonare(0,4 mg/kg/h).- The study was carried out at room temperature for 24 h. The standard mixture composition using EVA bag was: Dextrose 50%- 500 ml;Aminoacids 100 gr - 1000ml; Intralipidr 20% -500 ml; Na: 40 mmol;K: 70 mmol; Ca: 4,6 mmol; Mg: 5mmol; Phosphorus:17,5 mmol;Cl: 120 mmol, and acetat: 45 mmol.Volume: 2030 ml,pH: 6,5;0smolarity: 1200 mOs/l. A hypothetic patient' s weigth of 60 kg was taken. Bag 1: 1296 mg of Aminophylline (smokers dosage) were added to the finished TPN mixture. Bag 2: 1296 mg of Aminophylline added to the fat emulsion and mixed with the rest of components TPN.Bag 3:Idem bag 1 but 576 mg of Aminophylline (car pulmonare dosage).Bag 4: Idem bag 2 but 576 mg of Aminophylline.

The drop rate was 70 ml/h,Samples were taken at 0 hours,6 h,12 h, and 24 h. after the preparaticn.The concentrations of drugs in the TPN solutions were 62,8 mcgfml of Ami- nophylline and 27,9 mcgfml of Aminophylline.Recovered Theophylline(BO% of Aminophylline) was tested by enzimradioinmunoassay(EMIT) adapted to the RA-1000 x% Technicon Analizer. Stability of fat emulsions was tested by Coulter Cunter Channelyzer.

Conclusions: Using the studied concentrations theophylline is stable in NPT bags stored 24 h at room temperature whether theophylline is mixed with fat emulsions or not.

There is no significant difference if the theophylline is added to the fat. emul- sions or after preparing the TPN mixture,

p-55 ENTERAL FEEDING MIXTURES: DIRECT TOTAL NITROGEN DETERMINATION. Adami G.F., Surrma M., Camerini G., Repetto M. Istituto di Patologia Chirurgica - Universita di Genova

Total nitrogen concentration was evaluated in three artificial (Nutrisond, Peptinaut and Precision N) enteral feeding products and in three natural enteral feeding mixtures, which were set by the dietitian at different protein content. Analyses were carried out in fifty IO-40 mg samples by NA 1500 automatic nitrogen analyzer (Carlo Erba Strumenta- zione), which gives highly reproducible.data on nitrogen content in organic substances, values being fully comparable with the Kjeldahl method ones (1). As far as the artificial mixtures are concerned, values were very closely similar to the theoretical ones (Nutri- sond: .65% + .02, Peptinaut: 2.65% + .05, Precision N: 3.82% + .03). The very low coeffi-

cents of variation indicate the highly reproducibility of the-results. The strict correla tion between the sample weight and the gaschromatographic response and the low intercept values reflect the full homogeneity of the mixtures. In the three natural enteral feeding mixtures, the NA 1500 nitrogen concentration values were higher than the theoretical ones (.97% + .20 vs .76%, 1.04% + .I8 vs .70% and .86% + .12 vs .61% respectively). The poor homogeneity is demonstrated-by high values of the coefficents of variation. Furthermore, though a strict linear relationship between sample weight and gaschromatographic response has been found, the intercept values were remarkably higher than the ones observed for the artificial mixtures. In patients fed with natural mixtures, when nitrogen intake is only theoretically evaluated by the protein content, nitrogen balance studies could be

impaired for the poor homogeneity of the mixtures or for the presence of non proteic ni- trogen containing substances.

(1) Colombo B., Giazzi G., Am.Lab., 1982, 38-45.

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