Pharmacokinetic investigations of the marker active metabolites 4-methylamino-antipyrine and 4-amino-antipyrine after intramuscular injection of metamizole in healthy piglets

Pharmacokinetic profiles of the two major active metabolites of metamizole, 4-methylaminoantipyrine (MAA) and 4-aminoantipyrine (AA), after intravenous injection in cats

This study aimed to determine the pharmacokinetic profile of two active metabolites of metamizole (dipyrone), N-methyl-4-aminoanthypyrine (MAA) and 4-aminoanthypyrine (AA), after intravenous administration in cats. Eight healthy mixed-breed cats were intravenously administered metamizole (25 mg/kg). Blood samples were collected at predetermined time points for up to 48 h after administration. Information on behavioral changes in the animals and adverse effects was collected. Plasma aliquots were processed and analyzed using the ultra-performance liquid chromatography tandem mass spectrometry technique. A validated UPLC-MS/MS method was used to characterize the pharmacokinetics of MAA and AA. Salivation was identified as an adverse clinical sign. The mean maximal plasma concentrations of MAA and AA were 29.31 ± 24.57 μg/mL and 1.69 ± 0.36 μg/mL, with half-lives of around 4.98 and 14 h, respectively. The area under the plasma concentration curve values were 28.54 ± 11.33 and 49.54 ± 11.38 h*μg/mL for MAA and AA, respectively. The plasma concentration of MAA was detectable for up to 24 h and was smaller than AA. AA was detectable for >48 h. Results suggest that metamizole is converted into active metabolites in cats. Further PK/PD and safety studies should be performed before defining the dose or administration intervals for clinical use.

Pharmacokinetics of metamizole (dipyrone) as an add-on in calves undergoing umbilical surgery

This preliminary clinical investigation of the pharmacokinetic behavior of the main metamizole (dipyrone) metabolites 4-methylaminoantipyrine (4-MAA) and 4-aminoantipyrine (4-AA) in calves undergoing umbilical surgery is part of an already published main study. A single intravenous dose of metamizole was added to ketamine/xylazine/isoflurane anesthesia. Eight Simmental calves weighing 90 ± 10.8 kg and aged 47.6 ± 10.4 days received 40 mg/kg metamizole intravenously 10 minutes prior to general anesthesia. Blood samples were collected over 24 hours and analyzed for 4-MAA and 4-AA. Meloxicam was additionally given twice: 2.5 hours pre- and 20.5 hours postsurgically. The pharmacokinetic profile of 4-MAA was best fitted to a two-compartment model and was characterized by a fast distribution half-life and slow elimination half-life (t_½alpha = 5.29 minutes, t_½beta = 9.49 hours). The maximum concentration (C_max 101.63 μg/mL) was detected at the first measurement time point 15 minutes after administration. In contrast, 4-AA showed fast, high and biphasic plasma peak concentration behavior in five calves (2.54–2.66 μg/mL after 15–30 minutes, and 2.10–2.14 μg/mL after 2–3.5 hours) with a t_½beta of 8.87 hours, indicating a rapid distribution and subsequent redistribution from well-perfused organs. Alternatively, three calves exhibited a slower and lower monophasic plasma peak concentration (1.66 μg/mL after 6.5 hours) with a t_½beta of 6.23 hours, indicating slow accumulation in the intravascular compartment. The maximum concentration and area under the plasma concentration curve (AUC) of 4-AA were lower than those of 4-MAA. This metabolic behavior supports our already published data on clinical monitoring and plasma cortisol concentrations (PCCs). Compared to those of saline controls, lower PCCs correspond to the t_½alpha of 4-MAA. Data on T_max and t_½beta also match these clinical observations. However, further studies are required to assess the exact analgesic mechanism and potency of the metamizole metabolites in calves.

Bio-inspired PtNPs/Graphene nanocomposite based electrocatalytic sensing of metabolites of dipyrone

Noble metal nanoparticles are known to electrocatalyze various redox reactions by improving the electron transfer kinetics. In the present study, we have introduced a facile bioinspired synthesis of PtNPs and their integration for the formation of PtNPs/graphene nanocomposite using Psidium guajava (guava) leaves extract. Graphene used in nanocomposite formulation was synthesized by exfoliation of graphite in water/acetone (25:75 v/v) mixture followed by mechanical shearing using ultrasonication and microwave irradiation. PtNPs/graphene nanocomposite was drop-cast onto a glassy carbon electrode (GCE, 3 mm dia). The electrocatalytic activity of PtNPs/graphene nanocomposite was tested in a three-electrode system for sensing of metabolic products of dipyrone (DIP) formed through 1 e^- and 2 e^- transfer reactions. The modified electrode exhibited almost 50% reduction in electrode resistance. The limit of detection was found to be 0.142 μM with sensitivities of 0.820 and 0.445 μA․μM^-1cm^-2 for DIP concentration below and above 100 μM, respectively, using square wave voltammetry. The signal of sensing of metabolites of DIP was almost invariant in the presence of glucose, dopamine, uric acid, and ciprofloxacin; however, the response current was decayed by 20% within the 10th cycle. The sensing of DIP spiked in treated sewage-water and running tap-water samples was ∼100% recoverable and comparable with HPLC.

PK/PD modeling of flunixin meglumine in a kaolin-induced inflammation model in piglets

Flunixin is marketed in several countries for analgesia in adult swine but little is known about its efficacy in piglets. Thirty-two piglets (6-8 days old) were randomized to receive placebo saline (n = 11, group CONTROL) or flunixin meglumine intravenously at 2.2 (n = 11, group MEDIUM) or 4.4 (n = 10, group HIGH) mg/kg, 10 hr after subcutaneous injection of kaolin in the left metacarpal area. A hand-held algometer was used to determine each piglet's mechanical nociceptive threshold (MNT) from both front feet up to 50 hr after treatment (cut-off value of 24.5 newton). Serial venous blood samples were obtained to quantify flunixin in plasma using LC-MS/MS. A PKPD model describing the effect of flunixin on the mechanical nociceptive threshold was obtained based on an inhibitory indirect response model. A two-compartmental PK model was used. A significant effect of flunixin was observed for both doses compared to control group, with 4.4 mg/kg showing the most relevant (6-10 newton) and long-lasting effect (34 hr). The median IC50 was 6.78 and 2.63 mg/ml in groups MEDIUM and HIGH, respectively. The ED50 in this model was 6.6 mg/kg. Flunixin exhibited marked antinociceptive effect on kaolin-induced inflammatory hyperalgesia in piglets.

The using of a piglets as a model for evaluating the dipyrone hematological effects

BACKGROUND

Dipyrone (MET, metamizole) is a non-steroidal anti-inflammatory drug commonly used both in human and in veterinary medicine. After oral administration, is broken down rapidly to metabolites which largely retain the activity of the parent drug. Its metabolites have analgesic, antipyretic and anti-inflammatory effects.

RESULTS

The subjects were eight healthy male Large White post-suckling piglets, weighing between 5.0 to 7.4 kg, of ages 35 ± 10 days. The animals were administered MET (100 mg/kg) by an intramuscular (I.M.) injection. The study calculated the value of several hemorheological parameters. Significant impact of MET treatment (p < 0.05) was proven in case: activated partial thromboplastin time; ratio of activated partial thromboplastin time; hemoglobin; hematocrit; mean corpuscular hemoglobin; mean corpuscular volume; red blood cells volume; white blood cells volume; prothrombin time index.

CONCLUSIONS

In summation, our observations suggest that a piglet model is useful for studying the impact of MET on hemorheological parameters.