Pharmacokinetics and residue depletion of praziquantel in rice field eels Monopterus albus

LC-MS/MS Analyzing Praziquantel and 4-Hydroxypraziquantel Enantiomers in Black Goat Plasma and Mechanism of Stereoselective Pharmacokinetics

Praziquantel (PZQ) is the most effective treatment for schistosomiasis, commonly administered as a racemic mixture of the two enantiomers. Despite many reports on the pharmacokinetics of PZQ, the stereoselective pharmacokinetics of PZQ and its major metabolite 4-hydroxypraziquantel (4-OH-PZQ) remain poorly understood in goats. In this study, the chiral LC-MS/MS method was further optimized for separating and quantifying PZQ, trans-4-OH-PZQ, and cis-4-OH-PZQ and their enantiomers and then applied for the molecular pharmacokinetics of three analytes in black goat plasma. The findings showed that PZQ was rapidly absorbed and metabolized to 4-OH-PZQ. The Cmax of trans-4-OH-PZQ was about 3 times and 6 times higher than those of cis-4-OH-PZQ and PZQ, respectively. The stereoselectivity of the PZQ and cis-4-OH-PZQ enantiomers was insignificant in black goat plasma (p > 0.05), whereas the trans-4-OH-PZQ enantiomers exhibited obvious stereoselectivity (p < 0.05). The Cmax of S-trans-4-OH-PZQ were ~3.1 times higher than that of R-trans-4-OH-PZQ. Further computer simulations indicated that these differences in the stereoselectivity might mainly stem from the different binding energies of the corresponding R- and S-enantiomers of the target analytes to black goat plasma albumin. It has guiding significance for the research on the stereoselectivity of chiral veterinary drugs and their precision medication.

Pharmacokinetics of praziquantel and its metabolites in grass carp (Ctenopharyngodon idella) following the oral administration of a single bolus

The study aimed to evaluate and compare the routes and rates of the depletion of the antiparasitic praziquantel (PZQ), a derivative of pyrazinoisoquinoline, following its oral administration in grass carp (Ctenopharyngodon idella). We focused on the depletion of PZQ and its major metabolites - cis-hydroxy praziquantel (CPZQ) and trans-hydroxy praziquantel (TPZQ), in water, the plasma, hepatopancreas, kidney, muscle, and skin, following a single oral administration of PZQ in a concentration of 50 mg/kg. Fish were sampled before the drug administration and then eight times in the course of the 30-day-long experiment. Our results indicate the rapid absorption and elimination of PZQ and its metabolites in all the analysed matrices. The most PZQ-burdened tissue was the hepatopancreas, the gill and the skin. In all the samples, the concentration of the drug and its metabolites consistently declined over time. The residue of the parent compound was detected for the longest time in all the tissues. During the study, a significant (P < 0.01) correlation was found within the concentration of PZQ, CPZQ, and TPZQ in the water and all the biological matrices. It was also found that the PZQ residue was not detected below the maximum residue levels (i.e., 20 μg/kg) until 16 days after exposure in the muscle and skin.

Simultaneous determination of praziquantel and its main metabolites in the tissues of black goats and their residue depletion

Praziquantel (PZQ) is a pyrazino-isoquinoline compound with broad spectrum of activity against parasitic trematodes and cestodes, and a key veterinary drug in the parasitic disease control field. However, PZQ residues caused by non-conforming or excessive use in food-producing animals may pose a serious threat to human health. Herein, a simple, sensitive and reproducible LC-MS/MS method was developed for the simultaneous determination of praziquantel and trans- and cis-4-hydroxypraziquantel in black goat tissues to guide the reasonable use of PZQ. The mean recoveries for three target analytes were 71.2 ∼ 117.6%, and the limits of quantification were 1.0 μg/kg. Twenty-five healthy black goats were administered a single dose of praziquantel tablets at a dose of 35 mg/kg of body weight for residue elimination study, The results revealed that praziquantel and 4-hydroxypraziquantel were rapidly depleted in goat tissues and the elimination half-lives did not exceed 1 day in all tissues except for muscle and lung. It provides guidance for the establishment of maximum residue limit of praziquantel in goat.

The pharmacokinetic characteristics of sulfadiazine in channel catfish (Ictalurus punctatus) following oral and intravenous administrations

This study aimed to determine the bioavailability and pharmacokinetic parameters of sulfadiazine (SDZ) in channel catfish (Ictalurus punctatus) following oral gavage and intravenous injection. The healthy channel catfish were orally and intravenously administrated with SDZ solution at doses of 50 and 5 mg/kg, respectively. Plasma samples were determined by ultra-performance liquid chromatography with an ultraviolet detector. The results demonstrated that the concentration-time profile of SDZ after oral dosing was best described by a one-compartmental open model with first-order absorption. The absorption half-life (t_1/2Kα ), the elimination half-life (t_1/2Ke ), and the area under concentration-time profile (AUC_0-∞ ) were estimated to be 0.87 h, 29.04 h, and 1311.72 mg.h/L, respectively. After intravenous administration, the concentration-time curve of SDZ conformed to a two-compartmental open model without absorption. The distribution half-life (t_1/2α ), the elimination half-life (t_1/2β ), the apparent distribution volume (V_ss ), the total clearance (CL), and AUC_0-∞ were calculated to be 0.19 h, 14.24 h, 0.36 L/kg, 0.018 L/h/kg, and 277.12 mg.h/L, respectively. Finally, the bioavailability was estimated to be 47.33%. This study will provide some useful information for the modification of the dosage form of SDZ in aquaculture, and is partly beneficial for appropriate use of SDZ in the future.

Preparation and In Vitro/In Vivo Evaluation of Orally Disintegrating/Modified-Release Praziquantel Tablets

This study was designed to develop orally disintegrating/sustained-release praziquantel (PZQ) tablets using the hot-melt extrusion (HME) technique and direct compression, and subsequently evaluate their release in in vitro and in vivo pharmacokinetics. For the extrusion process, hypromellose acetate succinate (HPMCAS)-LG was the carrier of pure PZQ, with a standard screw configuration used at an extrusion temperature of 140 °C and a screw rotation speed of 100 rpm. Differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), powder X-ray diffraction (PXRD) and Fourier-transform infrared spectroscopy (FTIR) were performed to characterize the extrudate. Orally disintegrating/sustained-release praziquantel tablets (PZQ ODSRTs) were prepared by direct compression after appropriate excipients were blended with the extrudate. The release amount was 5.10% in pH 1.0 hydrochloric acid at 2 h and over 90% in phosphoric acid buffer at 45 min, indicating the enteric-coating character of PZQ ODSRTs. Compared with the pharmacokinetics of marketed PZQ tablets (Aipuruike^®) in dogs, the times to peak (T_max), elimination half-life (t_1/2λ) and mean residence time (MRT) were extended in PZQ ODSRTs, and the relative bioavailability of PZQ ODSRTs was up to 184.48% of that of Aipuruike^®. This study suggested that PZQ ODSRTs may have potential for the clinical treatment of parasitosis.

The Pharmacokinetics of Doxycycline in Channel Catfish (Ictalurus punctatus) Following Intravenous and Oral Administrations

The objective of this study was to investigate the bioavailability (BA) and pharmacokinetics (PK) of doxycycline (DC) in channel catfish (Ictalurus punctatus) following a single intravenous injection at 5 mg/kg and a single oral administration at 50 mg/kg at 24°C. The calculation of PK parameters was based on the software 3P97. The plasma samples were determined using ultra-performance liquid chromatography. Following oral administration, the multiple-peak phenomenon presented in concentration vs. time curve of DC at 2 h (107.01 mg/L), 8 h (55.07 mg/L), and 72 h (15.10 mg/L), respectively. The compartmental model cannot simulate the oral concentration vs. time profile beside a non-compartmental model. The calculated parameters of the elimination rate constant (λ_z), the elimination half-life (t_1/2λz ), and the area under the concentration vs. time curve (AUC_0-144) were 0.037 1/h, 18.91 h, and 2255.45 μg.h/mL, respectively. After intravenous administration, the concentration vs. time profile of DC was best described by a two-compartmental open model without absorption. The parameters of the distribution rate constant (α), the distribution half-life (t_1/2α), the elimination rate constant (β), the elimination half-life (t_1/2β), the apparent distribution volume at steady state (V_ss), the total clearance (Cl) and the area under the concentration vs. time curve (AUC_0-∞) were 2.79 1/h, 0.25 h, 0.042 1/h, 16.51 h, 300.00 mL/kg, 14.00 mL/h/kg, and 364.99 μg.h/mL, respectively. For the calculation of BA values at the same condition, the data obtained from intravenous injection were also iterated based on a non-compartmental model, and the corresponding parameters of λ_z, t_1/2λz , V_z, Cl, and AUC_0-144 were 0.019 1/h, 36.26 h, 480.00 mL/kg, 9.10 mL/h/kg, and 514.45 μg.h/mL, respectively. However, there was a considerable difference in the same parameter when calculated by compartmental and non-compartmental approaches. Finally, the medium BA value of DC was evaluated to be 43.84%. This study provides future studies with a framework for determining the BA of DC in the development of a new formulation and provides information on the appropriate use of DC in aquaculture.

Sulfadiazine pharmacokinetics in grass carp (Ctenopharyngodon idellus) receiving oral and intravenous administrations

This study aimed to examine the bioavailability (BA) and pharmacokinetic (PK) characteristics of sulfadiazine (SDZ) in grass carp (Ctenopharyngodon idellus) after oral and intravenous administrations. Blood samples were collected at predetermined time points of 0.083, 0.17, 0.5, 1, 2, 4, 8, 16, 24, 48, 72, and 96 hr (n = 6). The samples were extracted and purified by organic reagents and determined by the ultra-performance liquid chromatography. The software named 3P97 was used to calculate relevant PK parameters. The results demonstrated that the concentration-time profile of SDZ was best described by a one-compartmental open model with first-order absorption after a single oral dose. The main PK parameters of the absorption rate constant (K_α ), the absorption half-life (t_{1/2 Kα} ), the elimination rate constant (K_e ), the elimination half-life (t_1/2Ke ), and the area under concentration-time profile (AUC_0-∞ ) were 0.3 1/h, 2.29 hr, 0.039 1/h, 17.64 hr, and 855.78 mg.h/L, respectively. Following intravenous administration, the concentration-time curve fitted to a two-compartmental open model without absorption. The primary PK parameters of the distribution rate constant (α), the elimination rate constant (β), the distribution half-life (t_1/2α ), the elimination half-life (t_1/2β ), the apparent distribution volume (V_SS ), the total clearance (CL), and AUC_0-∞ were 9.62 1/hr, 0.039 1/hr, 0.072 hr, 17.71 hr, 0.33 L/kg, 0.013 L h^-1  kg^-1 , and 386.23 mg.h/L, respectively. Finally, the BA was calculated to be 22.16%. Overall, this study will provide some fundamental information on PK properties in the development of a new formulation SDZ in the future and is partially beneficial for the appropriate usage of SDZ in aquaculture.

Use of praziquantel to control platyhelminth parasites of fish

Fish are common definitive and intermediate hosts for a variety of parasitic flatworms. In unstressed wild populations, parasitic infections often go unnoticed and are perceived to represent a lesser threat to fish health. In contrast, platyhelminth parasitism of captive fish often results in decreased weight gain and increased mortality which often necessitates chemotherapeutic treatment. The presence of platyhelminth parasites in fish tissues is not only unappealing but in some cases also represents a threat to human health. In veterinary medicine, one of the most commonly used agents with anti-flatworm activity is praziquantel; yet, no praziquantel products are labeled for use in fish in the United States. Veterinarians may use praziquantel preparations approved for other vertebrate species under the Animal Medicinal Drug Use Clarification Act (AMDUCA). However, such extra-label use should be informed by scientific evidence including efficacy and tissue residue studies. Herein, we review studies testing the efficacy of praziquantel for treatment of platyhelminthes along with an assessment of routes of administration, pharmacokinetics, and toxicity information.