[Effect of feed antibiotics on ampicillin pharmacokinetics in chickens]. / Vliianie na niakoi nutritivni antibiotitsi vurkhu farmakokinetikata na ampitsilina pri pileta.

Experimental studies with broiler birds revealed that medicated feed (flavophospholipol, vitamyacin A, and the A-149 antibiotic in stimulative doses), offered in the course of two weeks, led to changes in the pharmacokinetic parameters of ampicillin administered i/v (in the form of ampicillin-Na) and via the crop (in the form of ampicillin-trihydrate at 30 mg/kg). It was found that the biologic half-life of ampicillin-Na was prolonged by A-149, and was shortened by vitamicin A, and to a certain extent--by flavophospholipol; the seeming volume of distribution was shown to rise by A-149, and to a certain extent--by flavophospholipol, and was lowered by vitamycin A. The biologic half-life of ampicillin-trihydrate was prolonged by all three ergotropic agents. The systematic bioavailability of ampicillin-trihydrate rose with the use of A-149, and dropped with the use of vitamycin A, and to a lower extent--with the use of flavophospholipol. On the base of the changes established in the pharmacokinetic parameters ampicillin-trihydrate was dosed for use via the drinking water as follows: 196 mg/l simultaneously with flavophospholipol in the feed, 156 mg/l--with the use of vitamycin A, 148 mg/l--when used with the A-149 antibiotic, and 216 mg/l--when administered at no medication via the feed.

Surface pressure hysteresis of mixed lipid/protein monolayers: applications to the alveolar dynamics.

Experimental data on surface pressure-surface area hysteresis of mixed serum albumin/dipalmitoyl lecithin/sphingomyelin monolayers in the Langmuir trough are presented. Several possible physicochemical mechanisms of the hysteresis are discussed: Marangoni effect, surface pressure relaxations, bulk-to-surface diffusion interchange, and collapse. Depending on the concrete conditions each of these mechanisms can be important. Possible applications of these results to the alveolar dynamics are presented and discussed on the basis of the balloon model of the alveolus. The main conclusions of biological importance are that 1) the alveolar stability depends on the DPL/SM ratio as well as on the protein content. Under normal breathing conditions the surface pressure hysteresis is small and does not play a decisive role in the alveolar dynamics. 2) At large extent of compression the collapse predominates in determining the hysteretic behavior of the alveolar surface.

[Pharmacokinetics, biological availability and residues of sulfadoxine and trimethoprim when used jointly on calves]. / Farmakokinetika, biologichna nalichnost i ostatuchni veshtestva na sulfadoksin i trimetoprim pri suvmestno prilagane na teleta.

In calves (cross-breds--Bulgarian Brown Cattle breed and Black Spot Cattle bred) weighing about 189 kg pharmacokinetics of sulphadoxine (SD) and trimethoprim (TMP) was studied. The two substances were administered in combination (5 + 1) as a dosage form Tridoxin (Pharmachim, Bulgaria; 24% injectable solution) (TD) at a dose 15 mg/kg m. The results show that after intramuscular administration TD is absorbed relatively rapidly. SD and TMP have systemic availability 94.1 +/- 18.1% and 52.5 +/- 6.2% and produce blood levels, after a single dose of TD, higher than potentiated minimum inhibitory concentrations for 24-48 h and 5(4-8) h, respectively. Upon intravenous administration the two-compartmental model is applicable for the distribution and elimination of SD and TMP (for TMP in part of the animals one-compartmental model is applicable). The two substances are distributed relatively widely in organs and tissues. The biological half-life of TD--t1/2 beta for SD is 14.36 +/- 1.40 h and for TMP--2.40 +/- 0.31 (for one-compartmental model--1.92 +/- 0.26) h, Vd--429.9 +/- 16.9 ml/kg and for TMP in part of the animals one-compartmental model is applicable). The two substances are distributed relatively widely in organs and tissues. The biological half-life of TD--t1/2 beta for SD is 14.36 +/- 1.40 h and for TMP--2.40 +/- 0.31 (for one-compartmental model--1.92 +/- 0.26) h, Vd--429.9 +/- 16.9 ml/kg and for TMP in part of the animals one-compartmental model is applicable). The two substances are distributed relatively widely in organs and tissues. The biological half-life of TD--t1/2 beta for SD is 14.36 +/- 1.40 h and for TMP--2.40 +/- 0.31 (for one-compartmental model--1.92 +/- 0.26) h, Vd--429.9 +/- 16.9 ml/kg and 655.8 +/- 77.6 (for one-compartmental model--671.7 +/- 40.0) ml/kg, ClB--0.35 +/- 0.02 ml/kg/min and 2.87 +/- 0.35 (for one-compartmental model--4.15 +/- 0.80) ml/kg/min, respectively. After intramuscular injection at the dose used a suitable withdrawal time for meat and internal organs is 5 days and for milk--2 days.

[Doxycycline hydrochloride administered in the drinking water to poultry]. / Doksitsiklinov khidrokhlorid, prilozhim s vodata za piene pri ptitsi.

Investigated were the acute toxicity, serum concentrations, and residual amounts of doxycycline in broiler chickens. It was found that the LD50 of doxycycline when applied via the crop to week-old broiler birds was 2500 mg/kg mass. The amount of 0.005 g/kg mass given orally to birds led to serum concentrations that on the eighteenth hour were found to drop up to subtherapeutic ones. When applied with the drinking water at the rate of 0.02 to 0.04 g l or kg feed it was well absorbed as early as the first hours. In such case the drug maintained therapeutic concentrations that were higher in the internal organs than those in the serum. The residual amounts of doxicycline hydrochloride when it was applied at 0.04 g/l of water or kg feed were found up to 48 h hour by the method of agar diffusion, using Bac. subtilis L2 as a test organism. The withdrawal time should amount to 72 hours.

[Tridoxin toxicity and tolerance in agricultural animals]. / Izsledvane vurkhu toksichnostta i ponosimostta ot selskostopanskite zhivotni na tridoksina.

It was found that LD50 of tridoxin (sulfadoxin-trimetoprim-5 + 1--State Economic Corporation Pharmachim) at i/m application to albino mica was 950 mg/kg, and of borgal (Hochst)--920 mg/kg. At oral application these values were 2650 and 2660 mg/kg, respectively. LD50 of tridoxin at i/m application to albino rats was 1075 mg/kg, and of borgal--1320 mg/kg; orally, these values were 3000 and 3260 mg/kg, respectively. When introduced into the crop of week-old broilers the LD50 values of fridoxin and borgal were 942 and 1670 mg/kg, respectively. The oral administration of tridoxin with the feed in 3 to 5 times higher amounts than was the therapeutic muscular dose to albino rats in the course of 30 days did not lead to clinical, clinical-and-biochemical, and histopathologic changes. The tolerance of tridoxin at a single i/m injection of a 5- times higher dose than the therapeutic one (0.075 g/kg) in the case of calves was good, with the exception of transient pain at the time of injection and shortly after that and the slight, transient slowing down of forestomach movements. The injection of amounts 3 and 5 times as high as the doses for pigs, sheep, and weaned lambs was tolerated well. The application to sheep was found to be more painful than in the case of calves and pigs.