Pharmacokinetics and bioavailability of doxycycline in ostriches (Struthio camelus) at two different dose rates

A Critical Review of the Pharmacokinetics, Pharmacodynamics, and Safety Data of Antibiotics in Avian Species

In avian medicine, the use of antibiotic dosing regimens based on species-specific pharmacological studies is ideal. However, due to a lack of such studies, dose extrapolation, which may cause inefficacy and toxicity, is common practice. Multiple searches were performed using the PubMed and Web of Science databases to extract relevant pharmacological studies performed in exotic avian species. The pharmacokinetics (PK), pharmacodynamics (PD), and safety data of the selected antibiotics (enrofloxacin, marbofloxacin, gentamicin, amikacin, ceftiofur, doxycycline, and amoxicillin/clavulanate) from these studies were reviewed. This review aimed to identify trends amenable for safe inter-species dose extrapolation and provide updated findings on dosing regimens that are safe and efficacious for various exotic avian species. We observed that the half-life of antibiotics appears to be shorter in the common ostrich and that amikacin may be amenable to inter-species dose extrapolation as it is safe and shows little inter-species PK and PD variation. Species-specific enrofloxacin dosing regimens that were not listed in the Exotic Animal Formulary (5th ed.) were found for Caribbean flamingos, African penguins, southern crested caracaras, common ostriches, and greater rheas. Specific dosing regimens recommended for psittacine birds (doxycycline 130 mg/kg medicated water) and ratites (PO doxycycline 2–3.5 mg/kg q12 h, PO enrofloxacin 1.5–2.5 mg/kg q12 h and IM enrofloxacin 5 mg/kg q12 h) in the formulary may not be effective in budgerigars and common ostriches, respectively. Apart from the lack of species-specific pharmacological studies, a lack of multiple dose studies was also noted.

Doxycycline pharmacokinetics in geese

The study aims to describe the pharmacokinetics of doxycycline after a single intravenous and oral dose (20 mg/kg) in geese. In addition, two multiple‐dose simulations have been performed to investigate the predicted plasma concentration after either a 10 or 20 mg/kg daily administration repeated consecutively for 5 days. Ten geese were enrolled in a two‐phase cross‐over study with a washout period of two weeks. All animals were treated intravenously and orally with doxycycline, and blood samples were collected up to 48 h after drug administration. Sample analysis was performed using a validated HPLC‐UV method. A non‐compartmental approach was used to evaluate the pharmacokinetic parameters of the drug. A long elimination half‐life was observed (13 h). The area under the curve was statistically different between the two treatments, with the oral bioavailability being moderate (43%). The pharmacokinetic/pharmacodynamic index (%T>MIC) during the 48 h treatment period in the present study (71%) suggests that doxycycline appears to have therapeutic efficacy against some Mycoplasma species in the goose. The multiple‐dose simulations showed a low accumulation index. A dosage of 10 mg/kg/day for 5 days seemed to be adequate for a good therapeutic efficacy without reaching unnecessarily high plasma concentrations.

In Vitro Comparative Quality Assessment of Different Brands of Doxycycline Hyclate Finished Dosage Forms: Capsule and Tablet in Jimma Town, South-West Ethiopia

Background

Persistent postmarket quality evaluation helps produce clear information on the current quality status of the different brands of a given drug and hence introduces a biopharmaceutical and therapeutically equivalent list of the products to the prescribers and users of it. This in turn facilitates access to essential medicines by breaking the high-cost barrier imposed by a few expensive brands of the product. This study was aimed at determining the quality and evaluating the equivalence of doxycycline hyclate capsules and tablets in Jimma, Ethiopia.

Methods

Ten brands of doxycycline hyclate capsules and tablets were tested for product identity, dosage uniformity, assay, and in vitro dissolution; and tablets were tested for friability and hardness.

Results

All investigated brands of doxycycline complied with the USP for dosage uniformity, an assay of the active ingredient, and single-point dissolution tests. One brand, D09, failed both hardness and friability tests. Comparisons of dissolution profiles applying fit factors confirmed that only brands D04, D06, and D07 had similarities with the innovator. Ratio test approaches also showed that significant variability exists between test products and comparators. Weibull model was found to provide the best adjustment curve for all brands, from model-dependent approaches employed for explaining the overall release of drug from the dosage forms.

Conclusions

Doxycycline is a biowaiver product. Hence, in vitro dissolution evaluation suffices its market approval. In this quality assessment study, however, the samples passed quality control tests, except D09 brand which failed friability; it has been revealed that five out of eight brands had problems with interchangeability. Only three doxycycline hyclate brands were found to be equivalent to the comparators.

Pharmacokinetics, bioavailability and tissue residues of doxycycline in Japanese quails (Coturnix coturnix japonica) after oral administration

This study aimed to determine the bioavailability, tissue residue and withdrawal time of doxycycline after oral administration in Japanese quails (Coturnix coturnix japonica). Japanese quails received doxycycline at 20 mg/kg dose following either single intravenous or oral administration, or 5-day oral administration. Doxycycline concentrations in plasma, liver, kidney, muscle, and skin + fat were determined using high-performance liquid chromatography-ultraviolet. The Withdrawal Time v1.4 software was used to calculate withdrawal times. Following single oral administration, terminal elimination half-life, area under the concentration-time curve from 0 to infinitive time, peak plasma concentration (C_max) and time to reach C_max were 10.98 h, 215.84 (h*µg)/mL, 15.33 μg/mL, and 2 h, respectively. The oral bioavailability was 25.84% in quails. In this study, the mean doxycycline concentration was below the maximum residue limit (MRL) at day 4 in skin + fat (0.120 µg/g), and at day 5 in kidney (0.41 µg/g), liver (0.26 µg/g), and muscle (<0.05 µg/g lowest limit of quantification). The highest concentrations of doxycycline after 5-day oral administration were found in kidney compared with other tissues and plasma. These results indicate that the withdrawal times required for doxycycline to reach concentrations <MRLs after 5-day oral administration at 20 mg/kg dose in Japanese quail are 6 days in Europe and China and 9 days in Japan.

[6]-Shogaol/β-CDs inclusion complex: preparation, characterisation, in vivo pharmacokinetics, and in situ intestinal perfusion study

Aims: The aim was to improve the absorption and bioavailability of [6]-shogaol with β-cyclodextrin (β-CD) prior to in vitro and in vivo evaluation. Methods: [6]-Shogaol/β-CDs inclusion complexes (6-S-β-CDs) were developed using saturated aqueous solution method and characterised with appropriate techniques. The absorption and bioavailability potential of [6]-shogaol was evaluated via in vivo pharmacokinetics and in situ intestinal perfusion. Results: The results of characterisation showed that 6-S-β-CDs (drug loading, 7.15%) were successfully formulated. In vitro release study indicated significantly improved [6]-shogaol release. Pharmacokinetic parameters such as Cmax, AUC0-36 h, and oral relative bioavailability (about 685.36%) were substantially enhanced. The in situ intestinal perfusion study revealed that [6]-shogaol was markedly absorbed via passive diffusion in the intestinal segments, and duodenum followed by ileum and jejunum. Conclusions: Cyclodextrin inclusion technology could enhance the intestinal absorption and oral bioavailability of hydrophobic drugs like [6]-shogaol.

Pharmacokinetics of doxycycline after oral administration of single and multiple dose in broiler chickens

As a semisynthetic tetracycline derivative, doxycycline (α-6-deoxy-5-hydroxytetracycline) is a time-dependent bacteriostatic agent. It is being widely used in the broiler husbandry in China. In this study, doxycycline was orally administered by gavage to 10 healthy broiler chickens at the dose of 20 mg/kg body weight every 24 hr for five total treatments. Plasma samples were collected from each animal at 5, 10, 20, and 30 min and 1, 2, 4, 6, 8, and 12 hr after the first dose, at 0.25, 0.5, 0.45, 1, 2, 3, 4, 6, 7, 13.5, 24, 36, 48, 60, and 72 hr after the last dose. Additional plasma samples were collected at a 24-hr interval during the dosing period (immediately prior to each oral administration). The doxycycline concentrations were determined by high-performance liquid chromatography with an ultraviolet detector and subjected to noncompartmental analysis. Then, the pharmacokinetics profiles were compared after the first and last oral doses. After the first dosing, the elimination half-life, area under the concentration-time curve from 0 hr to ∞, peak concentration, time to reach peak concentration, and volume of distribution per fraction absorbed were determined as 7.78 hr, 94.19 μg·hr/ml, 5.65 μg/ml, 3.50 hr, and 2,502.65 ml/kg, respectively, while the corresponding values of these parameters after the last dose were 19.90 hr, 121.08 μg·hr/ml, 5.71 μg/ml, 7.25 hr, and 5,285.28 ml/kg, respectively. After multiple oral doses, the absorption and elimination both became slower, while the distribution was more extensive than that following a single dose. However, after multiple oral doses, accumulation of doxycycline in plasma was not observed with an average accumulation factor of 1.11.

The influence of growth and E. coli endotoxaemia on amoxicillin pharmacokinetics in turkeys

1. This experiment aimed to determine if the pharmacokinetics of amoxicillin (AMO) was affected by rapid growth or intravenous (i.v.) injection of Escherichia coli lipopolysaccharide (LPS). 2. Turkeys of 2.0, 5.5 and 12.0 kg were administered i.v. or orally with AMO sodium at the dose of 15 mg/kg. Another group (5.7 kg) was treated with LPS prior to i.v. AMO administration. Plasma drug concentrations were determined using high-performance liquid chromatography and pharmacokinetic parameters were calculated using a non-compartmental model. To assess the haemodynamic effects of endotoxaemia, turkeys were subjected to echocardiography. 3. During growth from 2.0 to 5.5 kg, the area under the drug concentration-time curve after i.v. AMO administration increased from 9.37 ± 2.43 to 21.29 ± 5.49 mg×h/ml. Total body clearance decreased from 1.72 ± 0.55 to 0.75 ± 0.12 l/h/kg. Growth to 12.0 kg did not further affect these parameters. Mean residence time and elimination half-life gradually increased. Pharmacokinetics of orally administered drug followed a similar pattern. LPS injection affected stroke volume, heart rate and resistance index. However, it did not affect the pharmacokinetic profile of AMO in survivors. 4. It is concluded that rapid growth in turkeys affects AMO pharmacokinetics. Endotoxaemia, on the other hand, does not affect AMO elimination if compensatory mechanisms develop.

Pharmacokinetics of doxycycline after a single intravenous, oral or intramuscular dose in Muscovy ducks (Cairina moschata)

1. The pharmacokinetics of doxycycline in ducks were investigated after a single intravenous (IV), intramuscular (IM) or oral (PO) dose at 20 mg/kg body weight. 2. The concentrations of doxycycline in plasma samples were assayed using a high performance liquid chromatography method, and pharmacokinetic parameters were calculated using a non-compartmental model. 3. After IV administration, doxycycline had a mean (±SD) distribution volume (Vz) of 1761.9 ± 328.5 ml/kg and was slowly eliminated with a terminal half-life (t₁/₂λz) of 21.21±1.47 h and a total body clearance (Cl) of 57.51 ± 9.50 ml/h/kg. Following PO and IM administration, doxycycline was relatively slowly absorbed - the peak concentrations (Cmax) were 17.57 ± 4.66 μg/ml at 2 h and 25.01 ± 4.18 μg/ml at 1.5 h, respectively. The absolute bioavailabilities (F) of doxycycline after PO and IM administration were 39.13% and 70.71%, respectively. 4. The plasma profile of doxycycline exhibited favourable pharmacokinetics characteristics in Muscovy ducks, such as wide distribution, relatively slow absorption and slow elimination, though oral bioavailability was low.

Pharmacokinetic behavior of doxycycline after intramuscular injection in sheep

OBJECTIVE

To determine the pharmacokinetics of a commercial formulation of doxycycline hyclate after IM administration of a single dose to sheep.

ANIMALS

11 healthy domestic sheep.

PROCEDURES

For each sheep, doxycycline was administered as a single dose of 20 mg/kg, IM. Blood samples were obtained prior to and for 84 hours after doxycycline administration. Plasma concentrations of doxycycline were determined via high-performance liquid chromatography with UV detection. Pharmacokinetic data were analyzed with noncompartmental methods.

RESULTS

Mean ± SD values for pharmacokinetic parameters included maximum plasma concentration (2.792 ± 0.791 μg/mL), time to reach maximum plasma concentration (0.856 ± 0.472 hours), mean residence time (91.1 ± 40.78 hours), elimination half-life (77.88 ± 28.45 hours), and area under the curve (65.67 ± 9.877 μg•h/mL).

CONCLUSIONS AND CLINICAL RELEVANCE

Results indicated that doxycycline had prolonged absorption and elimination in sheep after IM administration. A daily dose of 20 mg/kg would be sufficient to reach effective plasma concentrations against Chlamydia spp (minimum inhibitory concentration, 0.008 to 0.031 μg/mL) and Staphylococcus aureus (minimum inhibitory concentration, 0.12 μg/mL). Doxycycline administered IM could be an option for therapeutic use in sheep, although further studies are needed.