摘要:

The pharmacokinetics and gastrointestinal distribution of ornately tart rate release from a sustained release trilaminate bolus in cattle were investigated over a 98‐day period post treatment. Six Holstein calves (125–150 kg) had permanent indwelling fistulae surgically inserted into the rumen, abomasum and terminal ileum. Samples of jugular blood, feces and ruminal, abomasal and ileal fluids were taken on days ‐3, 1, 4, 7, 10, 14 and weekly up to 98 days post‐bolus administration. Morantel tartrate concentrations were measured by HPLC after extraction and clean‐up. Morantel was not detected in plasma at any time after bolus administration. High concentrations of morantel tartrate were found in ruminal, abomasal and ileal fluids and feces over 98 days post‐treatment. The morantel peak concentration (Cmax) was achieved at Day 1 post‐administration in each of these compartments. The steady‐state morantel concentration (Csswas achieved at approximately 10 days post‐treatment and maintained for 91–98 days post‐treatment in these gastrointestinal compartments. The morantel CmaxCss, area under the zero (AUC) and first moment (AUMC) of the concentration‐time curve were significantly higher (P<0.01) in feces than in other compartments. Thein vivodrug release profile of this device has been determined. Steady‐state concentrations for from 91 to 98

ISSN:0140-7783    

DOI:10.1111/j.1365-2885.1992.tb00998.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

The effects of time and method of administration of rifampin with respect to feeding were evaluated in five mature horses. There was a significant (P ≤ 0.05) delay in time of maximum serum concentration and an apparent but not significant decrease in oral absorption when rifampin was given as a top dressing on grain as compared with administration in corn syrup 2 h before or 2 h after feeding. Although there were no differences between administration before or after feeding, administration 2 h prior to feeding was selected as the method of choice for future experiments. The effects of age on rifampin disposition were subsequently examined using this method of administration in six, 1‐week old foals. Rifampin (10 mg/kg) was given at increasing age from 1 through 10 weeks and the pharmacokinetic disposition parameters compared. There were significant differences in the slope of the elimination phase (p) and area under the curve (AUC) at 1 week through 6 weeks compared with 10 weeks or with values in the five mature hor

ISSN:0140-7783    

DOI:10.1111/j.1365-2885.1992.tb00999.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

The pharmacokinetics of amikacin were studied in healthy mature female chickens (n =6). Single doses of amikacin were injected as an i.v. bolus (10 mg/ kg) and im. (20 mg/kg) into the same birds with a 30‐day rest period between treatments. Amikacin was determined by the fluorescence polarization im‐munoassay method. The i.v. pharmacokinetics could be described by a two‐compartment model with a t1/2αof 0.150 ± 0.064 h and a t1/2βof 1.44 ± 0.34 h. The total body clearance was 0.109 ± 0.017 l/h/kg and the volume of distribution at steady‐state was 0.193 ± 0.060 Vkg. Following a single i.m. injection. the peak plasma concentration (Cmax) was 50.79 ± 4.05 μg/ml and occurred at 0.50 ± 0.26 h. The i.m. extent of absorption was 91.2 ± 17.65%. Simultaneous modeling of i.v. antl i.m. results provided estiinates of an absorption half‐life of 0.480 ± 0.158 h.The i.m. pharmacokinetics after repeated administration were stittlied following the tenth close (20 mg/kg, every 8 h). The Cssmaxwas 38.58 ± 6.96 pgi nil and occurred at 0.79 ± 0.37 11, and the biological half‐life of aniikncin was 1.86 5 0.47 11. The multiple closing yielded peak concentrations of 39 μg/ml and trough concentrations of 3.26 μg/ml. Based on these data, the recomnienclecl amikacin dosage in chickens is 20 m

ISSN:0140-7783    

DOI:10.1111/j.1365-2885.1992.tb01000.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Most drugs used for the treatment of birds are not formulated for birds. Therefore the availability of drugs for birds and their administration routes largely depend on formulations available for man, mammals and to some extent poultry. The problems with the application of existing formulations, the drug concentrations and the many different avian species are discussed.The desire of the avian veterinarian for the combination of several active compounds presents special problems. This again requires extra data on the interactions in galenic, pharmaceutic, pharmacokinetic and dynamic phases, which are generally not readily available.

ISSN:0140-7783    

DOI:10.1111/j.1365-2885.1992.tb01001.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Differences in bioavailability of many drugs from their various dosage forms have been shown to be relatively common in human medicine. Although comparable bioavailability (‘bioequivalence’) is thought to ensure comparable clinical effectiveness and safety (‘therapeutic equivalence’), the relationship between bioinequivalence and therapeutic inequivalence is less clear. Thus the prevalence of clinically important differences in bioavailability is unknown. While similar concerns have arisen about drug products used in small animal practice, there have been few investigations and some earlier reports are incomplete. However, there are indications of bioinequivalence with enteral formulations of ampicillin, aspirin, chloramphenicol, digoxin, rnitotane, oxytet‐racycline, penicillin V and theophylline. Other studies have suggested bioequivalence with enteral formulations of chloramphenicol, digoxin, phenytoin, oxytetracycline and thyroxine. Limited data for injectable preparations showed bioinequivalence with chloramphenicol and possibly oxytetracycline. There is no reason to expect formulation‐related bioinequivalence to be less prevalent in veterinary than in human medicine. Indeed, it may be more common in veterinary practice because other potential influences on bioavailability (food, diseases, other drugs, etc.) are frequently ignored, and cheaper generic products are often favoured for econo

ISSN:0140-7783    

DOI:10.1111/j.1365-2885.1992.tb01002.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

The route of administration and formulation of the dosage form affect the bioavailability (rate and extent of absorption) of a drug and may thereby influence the intensity and duration of the pharmacological effect. Location of injection site may affect the plasma concentration profile of drugs administered as aqueous suspensions or sustained release potential preparations (procaine penicillin G). When absorption influences the rate of elimination (‘flip‐flop’ phenomenon), the apparent half‐life of the drug will be increased (cefazolin sodium, i.m.; meclofenamic acid, p.o.).Absorption generally approximates a first‐order process and either the absorption half‐life or the mean absorption time (statistical moment term) will provide an estimate of the rate of absorption. The method of corresponding areas is the usual technique employed in estimating the extent of absorption (systemic availability). Inherent in this technique is the assumption that clearance of the drug remains unchanged. In horses, the time of feeding relative to oral dosing has been shown to affect systemic availability (rifampin, trimethoprim) and pattern of absorption (phenylbutazone). Oral paste formulations (trimethoprim‐sulphadiazine, ivermectin) are convenient to administer, allow precision in dosage compared with powders or granules added to feed, and could provide sustained release.Assessment of bioequivalence is based on relative bioavailability, using a reference dosage form, together with a measure of the uncertainty (variance) of the estimate. Bioequivalence relies on the concept that preparations of a drug which provide essentially equivalent plasma concentration profiles should produce the same thera

ISSN:0140-7783    

DOI:10.1111/j.1365-2885.1992.tb01003.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Total respiratory resistance was measured rapidly and non‐invasively in 6 conscious ponies before and after they inhaled approximately 25% of the minimal anaesthetic concentration (0.25 MAC) of either enflurane, halothane, or isoflurane, over a 10 min period. The forced random noise (FRN) method was used to measure the impedance over the frequency range of 5 to 40 Hz and its real part, the resistance, was extracted from these impedance measurements. At the concentrations used, halothane appeared to have no effect on the total respiratory resistance; enflurane and isoflurane seemed to increase it but the changes were not statistically significan

ISSN:0140-7783    

DOI:10.1111/j.1365-2885.1992.tb01004.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

The prescribing of drugs for food‐producing animals in Norway was investigated with special emphasis on written information given about withdrawal times. The study was designed as a cross‐sectional prescription survey.Of 1518 prescriptions for food‐producing animals, it was concluded that 1224 of the prescriptions were for drugs requiring withdrawal times for meat, milk or eggs. Of these 1224 prescriptions, 82.8% were for veterinary preparations, 6.6% were for human preparations and 10.6% were for other drugs.For 20.8% of the prescriptions, information about withdrawal time(s) was missing. For prescriptions for veterinary preparations this figure was 5.9%, and for prescriptions for human preparations and other drugs 95.1% and 90.8%, respectively. For veterinary preparations approved for the intended species, as many as 99.2% gave information about withdrawal times on the drug container label.Lack of information about withdrawal times might give rise to drug residues in food for human consumption and thus pose a potential hazard to human h

ISSN:0140-7783    

DOI:10.1111/j.1365-2885.1992.tb01005.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Several antibiotics characterized by different molecular structures are known to affect some intestinal activities. Some of them have been described as inhibitors of the intestinal sugar and amino iced transport with different mechanisms. Erythromycin (EM) is a rnacrolide antibiotic acting as a motilin agonist and thus stimulating the gastrointestinal motor activity. Since several substances which increase the motor activity of the gastrointestinal tract may produce effects on the intestinal absorption of nutrients, the present study has been carried out to determine whether erythromycin affects the L‐threonine intestinal absorption. The results obtained indicate that erythromycin diminishes the L‐threonine intestinal transport, probably at the mucosal border level. Two groups of experiments carried out, with Na+‐deprived medium and ouabain‐enriched medium, might indicate that erythromycin action could be due to either a direct or an indirect action on the Na+‐dependent r‐threonine transport located in the b

ISSN:0140-7783    

DOI:10.1111/j.1365-2885.1992.tb01006.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

The sedative effects of a new α2‐adrenoceptor agonist, romifidine, were compared with those of xylazine and detomidine. Five horses were treated with two doses of romifidine (40 μg/kg body weight and 80 μg/kg body weight), two doses of detomidine (10 μg/kg body weight and 20 μg/kg body weight) and one dose of xylazine (1 mg/kg body weight) given by intravenous injection using a Latin‐square design.The dose of 80 μg/kg romifidine appeared equipotent to 1 mg/kg xylazine and 20 μg/kg detornidine, although at these doses both xylazine and detomidine had a shorter action. Detomidine 20 μglkg and xylazine both produced greater lowering of the head and a greater degree of ataxia than romifidine at either dose. Romifidine produced sedation similar to that of the other drug regimes. The effect upon imposed stimuli

ISSN:0140-7783    

DOI:10.1111/j.1365-2885.1992.tb01007.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY