Pharmacokinetics and urinary excretion of sulphadimidine in sheep during summer and winter

Pharmacokinetics of Salicylic Acid Following Intravenous and Oral Administration of Sodium Salicylate in Sheep

Simple Summary

Scarcity of non-steroidal anti-inflammatory drugs (NSAID) to minimise the pain in sheep instigated the current study. The aim of this study was to know the pharmacokinetic parameters of salicylic acid in New Zealand sheep after administration of multiple intravenous and oral doses of sodium salicylate (sodium salt of salicylic acid). Results of the study suggest that the half-life of the drug was shorter and clearance was faster after intravenous administration as compared to that of the oral administration. The minimum effective concentration required to produce analgesia in humans (16.8 µL) was achieved in sheep for about 0.17 h in the current study after intravenous administration of 100 and 200 mg/kg body weight of sodium salicylate. However, oral administration of these doses failed to achieve the minimum effective concentration as mentioned above. This study is of significance as it adds valuable information on pharmacokinetics and its variation due to breed, species, age, gender and environmental conditions. As per the authors’ knowledge, this is the only study showing detailed information about absorption, distribution and elimination of salicylic acid in New Zealand Sheep. An intravenous administration of sodium salicylate at 100 and 200 mg/kg dose may produce analgesia in sheep, which requires further investigation using pharmacokinetic–pharmacodynamic (PKPD) integration or modelling techniques.

Abstract

The pharmacokinetics of salicylic acid (SA) in sheep was evaluated following intravenous (IV) and oral administration of sodium salicylate (sodium salt of salicylic acid) at different doses. Six healthy sheep were administered sodium salicylate (SS) IV at doses of 10, 50, 100 and 200 mg/kg body weight and another six sheep were drenched with 100 and 200 mg/kg of SS orally. Both studies were randomised crossover trials. A one-week washout period between each treatment was allowed in both studies. Blood samples were collected at 0, 15, 30 min and 1, 2, 4 and 6 h after IV and oral SS administrations. Plasma SA concentrations were determined using high-performance liquid chromatography (HPLC) with diode array detection method. Pharmacokinetic variables were calculated in a non-compartmental model. The elimination half-life (T_{1/2 el}) of SA after IV administration of 200 mg/kg SS was 1.16 ± 0.32 h. Mean bioavailability of SA was 64%, and mean T_{1/2 el} was 1.90 ± 0.35 h, after 200 mg/kg of oral SS. The minimum plasma SA concentration (16.8 µg/mL) reported to produce analgesia in humans was achieved after IV administration of 100 and 200 mg/kg SS in sheep for about 0.17 h in this study. Experiments on pharmacokinetic–pharmacodynamics modelling are required to determine the actual effective plasma concentration range of SA in sheep.

Pharmacokinetic comparison of sustained- and immediate-release oral formulations of cilostazol in healthy Korean subjects: a randomized, open-label, 3-part, sequential, 2-period, crossover, single-dose, food-effect, and multiple-dose study

BACKGROUND

A sustained-release (SR) formulation of cilostazol was recently developed in Korea and was expected to yield a lower C(max) and a similar AUC to the immediate-release (IR) formulation.

OBJECTIVE

The goal of the present study was to compare the pharmacokinetic profiles of a newly developed SR formulation and an IR formulation of cilostazol after single- and multiple-dose administration and to evaluate the influence of food in healthy Korean subjects. This study was developed as part of a product development project at the request of the Korean regulatory agency.

METHODS

This was a randomized, 3-part, sequential, open-label, 2-period crossover study. Each part consisted of different subjects between the ages of 19 and 55 years. In part 1, each subject received a single dose of SR (200 mg × 1 tablet, once daily) and IR (100 mg × 2 tablets, BID) formulations of cilostazol orally 7 days apart in a fasted state. In part 2, each subject received a single dose of the SR (200 mg × 1 tablet, once daily) formulation of cilostazol 7 days apart in a fasted and a fed state. In part 3, each subject received multiple doses of the 2 formulations for 8 consecutive days 21 days apart. Blood samples were taken for 72 hours after the dose. Cilostazol pharmacokinetics were determined for both the parent drug and its metabolites (OPC-13015 and OPC-13213). Adverse events were evaluated through interviews and physical examinations.

RESULTS

Among the 92 enrolled subjects (66 men, 26 women; part 1, n = 26; part 2, n = 26; part 3, n = 40), 87 completed the study. In part 1, all the primary pharmacokinetic parameters satisfied the criterion for assumed bioequivalence both in cilostazol and its metabolites, yielding 90% CI ratios of 0.9624 to 1.2323, 0.8873 to 1.1208, and 0.8919 to 1.1283 for C(max) and 0.8370 to 1.0134, 0.8204 to 0.9807, and 0.8134 to 0.9699 for AUC(0-last) of cilostazol, OPC-13015, and OPC-13213, respectively. In part 2, food intake increased C(max) and AUC significantly (P < 0.0001), yielding geometric mean ratios of 3.2879, 2.9894, and 3.0592 for C(max) and 1.7001, 1.7689, and 1.6976 for AUC(0-last) of cilostazol, OPC-13015, and OPC-13213. In part 3, only the C(ssmax) of clilostazol in the reference formulation did not satisfy the criterion for assumed bioequivalence, yielding 90% CI ratios of 1.2693 to 1.4238 and 1.2038 to 1.3441, respectively. When each dose was normalized, the C(max) for the SR formulation was significantly lower (P < 0.005 for cilostazol). Headache was the most frequently noted adverse effect (part 1, a total of 14 subjects with the IR formulation and 14 with the SR formulation; part 2, a total of 10 without food and 23 with a high-fat meal; part 3, a total of 10 with the IR formulation and 24 with the SR formulation), followed by nausea (part 1, none; part 2, only 1 without food and 3 with a high-fat meal; part 3, a total of 3 with the IR formulation and 3 with the SR formulation), and then dizziness (parts 1 and 2, none; part 3, a total of 4 with the IR formulation and 5 with the SR formulation). All other AEs, including fever, cough, vomiting, palpitation, diarrhea, and epigastric pain, occurred in <3 subjects.

CONCLUSIONS

These findings suggest that in this select group of healthy Korean volunteers, the SR formulation of cilostazol was not significantly different in AUC compared with that of the IR formulation, although it did display a significantly lower C(max) per dose in both the single- and multiple-dose groups. Food significantly increased the bioavailability of the SR formulation. The cilostazol SR and IR formulations were well tolerated in all parts of the study, with no serious adverse events reported. ClinicalTrials.gov identifier: NCT01455558.

Daily rhythms in blood and milk lead toxicokinetics following intravenous administration of lead acetate to dairy cows in summer

The objective of this study was to investigate circadian variations of blood and milk lead toxicokinetics in dairy cows in summer. Twenty lactating Holstein animals were randomly assigned to four treatments corresponding to different hours after onset of light (HALO): 2, 8, 14, and 20. Cows received a single intravenous administration of 2.5 mg/kg lead as lead acetate. Blood and milk samples were taken and analyzed by atomic absorption spectrophotometry. For each toxicokinetic parameter, a one-way analysis of variance (ANOVA) was performed to outline the existence of daily variations. Significant blood differences as a function of HALO were found for the hybrid constant of distribution (alpha), hybrid constant of elimination (beta), elimination half-life (t(1/2)beta), area under the curve (AUC), volume of distribution at steady state (V(ss)) and clearance (Cl(B)) (p<0.05). Half-life of elimination presented two peaks at 2 and 14 HALO. Milk data showed significant differences for maximum concentration and AUC (p<0.05). The ratio AUC(milk)/AUC(blood) was utilized to estimate penetration of lead in milk. It differed significantly throughout the day (p<0.05). Milk data for the significant parameters could be fitted to circadian rhythms. No circadian rhythms were detected in blood parameters or in the ratio AUC(milk)/AUC(blood).

Disposition kinetics of erythromycin in normal and experimentally-induced febrile rabbits

The disposition kinetics of erythromycin were determined in normal and endotoxin-induced febrile rabbits following intravenous injection of a single dose of 10 mg/kg body weight. In febrile rabbits, body weight, blood pH, total lipids and total proteins in plasma remained unchanged, packed cell volume, albumin and the albumin/globulin ratio reduced while glucose and globulins increased significantly. The mean plasma drug concentration was lower under febrile conditions at all the sampling times except at 480 and 720 min after drug administration where the levels remained the same. The values for t1/2elim and MRT of the drug were observed to be prolonged while that of the Clt reduced and Vd increased in the febrile rabbits. The febrile condition resulted in an alteration in the disposition kinetics of erythromycin suggesting an adjustment of the dosage under febrile conditions.

Pharmacokinetics and pharmacodynamics of tilmicosin in sheep and cattle

Tilmicosin is a long-acting macrolide antibiotic currently approved for treatment of bovine respiratory disease in the USA. Serum pharmacokinetics of tilmicosin were compared between cattle (major species) and sheep (minor species) after subcutaneous injection in order to evaluate a new potential application of the drug in currently nonapproved species. There were no significant differences in the elimination rates, maximum serum concentrations, half-lives (t1/2), areas under the curve (AUC), areas under the first-moment curve (AUMC), and mean residence times. Volume of distribution (Vd(area)) and clearance (Cl), when normalized by body weight, were also similar. The only significantly different parameter was time at which maximum drug concentration was reached (tmax), with sheep having the tmax of 3.9 h, compared to 0.5 h in cattle. Although macrolides are considered to be one of the safest anti-infective drugs, adverse cardiovascular effects of several macrolides have been reported. The cardiopulmonary effects of tilmicosin were monitored in healthy adult sheep after receiving a single subcutaneous (s.c.) injection of tilmicosin at the dose of 10 mg/kg, and no significant changes were found. The study indicates that tilmicosin can be used safely and effectively in sheep at the given dose, with no adverse cardiopulmonary effects.

The effect of water deprivation on the pharmacokinetics of antipyrine and sulphadimidine following intravenous administration in Nubian goats

The effect of water deprivation on the pharmacokinetic parameters of antipyrine and sulphadimidine in the Nubian goat was studied. Water deprivation, to a level of dehydration at which the animals lost an average of 7.5% body weight, resulted in a significant reduction in antipyrine clearance (p < 0.05), and a consequently increased AUC value (p < 0.05). No effect was observed on the distribution parameters of the drug. In dehydrated animals which had lost an average of 10% or 12.5% of their body weight owing to water deprivation, significant changes were found in the distribution and elimination pharmacokinetic parameters of antipyrine and sulphadimidine. The volume of distribution was significantly decreased, resulting in elevated plasma levels for the two drugs compared to normally watered animals. Significant decreases in clearance and subsequent prolongation of the elimination half-lives were observed during these periods of water deprivation. These changes in the disposition kinetics of the two drugs may be attributed to the loss of total body water and extracellular fluids and changes in the liver and kidney functions taking place during dehydration.

Pharmacokinetics of antipyrine and sulphadimidine (sulfamethazine) in camels, sheep and goats

The pharmacokinetics of antipyrine and sulphadimidine were studied in male camels, sheep and goats. The two drugs were administered concomitantly. Following intravenous injection of antipyrine (25 mg/kg) and sulphadimidine (sulfamethazine) (100 mg/kg), the pharmacokinetics of the two drugs were adequately described by a one-compartment model. Antipyrine half-life in goats (2.58 h) was shorter than that in sheep (4.04 h) and camels (18.78 h). The plasma clearance was greatest in goats then sheep and then camels. For sulphadimidine, a significantly greater volume of distribution was observed in camels and the greatest plasma clearance and shortest half-life were reported in goats. Sulphadimidine half-life was 2.77 h in goats, 4.72 h in sheep and 7.36 h in camels. The present results suggest that goats have the fastest elimination of these drugs from the circulation, followed by sheep and then camels.

Pharmacokinetics, safety and tissue residues of sustained-release sulfamethazine in sheep

Concentration-time profiles and the rates of absorption, extent of distribution and half-lives of sulfamethazine (SMZ), administered intravenously, orally as a water solution and as a sustained-release formulation (CalfSpan) were determined in 10 healthy sheep. The geometric mean half-life of elimination of i.v. SMZ was 10.8 h, compared to 14.3 h for the sustained-release preparation (CalfSpan) and 4.3 h for the oral water solution. Blood levels of SMZ were at or above 50 micrograms/ml for more than 48 h for CalfSpan, for 24 h after i.v. SMZ (100 mg/kg body wt), and for less than 24 h after p.o. SMZ (100 mg/kg body wt). The mean bioavailability of the oral SMZ solution was 58.3% (AUCp.o./AUCi.v.). The estimated bioavailability of the CalfSpan preparation was 52.5%. The safety of the sustained-release preparation was tested by dosing sheep with multiples (one, three and five times) of the recommended dose (one tablet, 8 g SMZ, per 20 kg body wt), once a day for 3 days. Clinical blood chemistries showed a significant increase in serum iron, and a decrease in serum phosphorus in animals treated at the 3x and 5x dose levels. Necropsies of the 5x dose animals did not show any gross signs that could be attributed to SMZ, and histological examination of tissues from the 5x animals revealed no organ pathology. Residues of SMZ in liver, fat, kidney and skeletal muscle were measured in 20 animals that received one bolus per 20 kg body wt. The results indicate that SMZ residues are cleared rapidly, and are at or below the tolerance level of 0.1 mg/kg within 8 days after dosing so that the 18-day withdrawal time used in cattle would provide an appropriate margin of safety if used in sheep.

The effect of food deprivation on the rate of sulfamethazine elimination in goats

The disposition kinetics and cumulative urinary excretion of sulfamethazine were compared in goats fed normally (control) and following a 72-hour period of starvation (fasting). The only pharmacokinetic parameter which showed a statistically significant difference between the two groups was the body (systemic) clearance. This decreased from 2.26 +/- 0.28 ml/min.kg (means +/- SD, n = 6) in the control group to 1.16 +/- 0.54 ml/min.kg in the fasting group (p less than 0.01). Since the apparent volume of distribution was not affected by starvation, the decreased clearance was attributed to slower metabolism of the drug. Because of the analytical method used to measure sulfamethazine concentrations in plasma and urine, no conclusion could be drawn as to whether the rates of hydroxylation or of acetylation, or both metabolic pathways were decreased in the starved condition.

Food Animal Residue Avoidance Databank (FARAD): a pharmacokinetic-based information resource

The Food Animal Residue Avoidance Databank (FARAD) is a pilot project funded through the USDA Extension Service. It represents a major effort to compile into a single source large amounts of information on veterinary pharmaceutics, pharmacokinetics and physiochemical properties of drugs and other chemicals used in livestock production. FARAD is a computer-based system consisting of five data and numerous command files that access the data files to facilitate rapid input and retrieval of the desired information. The data files include proprietary information on all pharmaceutical products approved for use in food animals in the United States; physicochemical information on more than 100 chemicals contained in the databank; regulatory information pertaining to tolerance and action levels of chemical residues in animal products and allowable concentrations of drugs in feed; pharmacokinetic rate and volume constants pertinent to residue depletion modeling in a variety of species; bibliographic citations to which all of the information contained in the databank is referenced. All of the information in FARAD is currently available through three regional access centers in the United States, and direct computer access to the data may become available in the future.