High-performance liquid chromatographic assay for metamizol metabolites in rat plasma: Application to pharmacokinetic studies

Metamizole (MT) is an analgesic and antipyretic drug labelled for use in humans, horses, cattle, swine and dogs. MT is rapidly hydrolysed to the active primary metabolite 4-methylaminoantipyrine (MAA). MAA is formed in much larger amounts compared with other minor metabolites. Among the other secondary metabolites, 4-aminoantipyrine (AA) is also relatively active. The aim of this research was to evaluate the pharmacokinetic profiles of MAA and AA after dose of 25 mg/kg MT by intravenous (i.v.) and intramuscular (i.m.) routes in healthy horses. Six horses were randomly allocated to two equally sized treatment groups according to a 2 × 2 crossover study design. Blood was collected at predetermined times within 24 h, and plasma was analysed by a validated HPLC-UV method. No behavioural changes or alterations in health parameters were observed in the i.v. or i.m. groups of animals during or after (up to 7 days) drug administration. Plasma concentrations of MAA after i.v. and i.m. administrations of MT were detectable from 5 min to 10 h in all the horses. Plasma concentrations of AA were detectable in the same range of time, but in smaller amounts. Maximum concentration (C ), time to maximum concentration (T ) and AUMC of MAA were statistically different between the i.v. and i.m. groups. The AUC /AUC ratio of MAA was 1.06. In contrast, AUC of AA was statistically different between the groups (P < 0.05) with an AUC /AUC ratio of 0.54. This study suggested that the differences in the MAA and AA plasma concentrations found after i.m. and i.v. administrations of MT might have minor consequences on the pharmacodynamics of the drug.

Section: Methodsmentioning

confidence: 97%

Pharmacokinetic profiles of the active metamizole metabolites in healthy horses

Giorgi

Aupanun

Lee

et al. 2016

“…The analytical method was approached based on previously described methods with slight modifications (Domínguez‐Ramírez et al., ; Giorgi et al., ). The HPLC system was an LC Jasco (Como, Italy) consisting of a quaternary gradient system (PU 2089 PLUS), coupled with an ultraviolet detector (Jasco UV‐975) set at 254 nm.…”

Section: Methodsmentioning

confidence: 99%

Pharmacokinetic profiles of the active metamizole metabolites after four different routes of administration in healthy dogs

Giorgi

Łebkowska‐Wieruszewska

Lisowski

et al. 2018

Metamizole (MT), an analgesic and antipyretic drug, is rapidly hydrolyzed to the active primary metabolite 4-methylaminoantipyrine (MAA) and relatively active secondary metabolite 4-aminoantipyrine (AA). The aim of this study was to assess the pharmacokinetic profiles of MAA and AA after dose of 25 mg/kg MT by intravenous (i.v.), intramuscular (i.m.), oral (p.o.), and rectal (RC) routes in dogs. Six dogs were randomly allocated to an open, single-dose, four-treatment, four-phase, unpaired, crossover study design. Blood was collected at predetermined times within 24 hr, and plasma was analyzed by a validated HPLC-UV method. Plasma concentrations of MAA and AA after i.v., i.m., p.o., and RC administrations of MT were detectable from 5 (i.v. and i.m.) or 30 (p.o. and RC) min to 24 hr in all dogs. The highest concentrations of MAA were found in the i.v., then i.m., p.o., and RC groups. Plasma concentrations of AA were similar for i.v., i.m., and RC, and the concentrations were approximately double those in the PO groups. The AUC ratio for MAA was 0.75 ± 0.11, 0.59 ± 0.08, and 0.32 ± 0.05, for i.m., p.o., and RC, respectively. The AUC ratio for AA was 1.21 ± 0.33, 2.17 ± 0.62, and 1.08 ± 0.19, for i.m., p.o., and RC, respectively. Although further studies are needed, rectal administration seems to be the least suitable route of administration for MT in the dog.

“…The HPLC analysis was performed based on a previous study with some modifications (Domínguez-Ramírez et al, 2012;Giorgi et al, 2015).…”

Section: Hplc Analysismentioning

confidence: 99%

Pharmacokinetic profiles of the two major active metabolites of metamizole (dipyrone) in cats following three different routes of administration

Łebkowska‐Wieruszewska

Kim

Chea

et al. 2017

This study was performed to determine pharmacokinetic profiles of the two active metabolites of the analgesic drug metamizole (dipyrone, MET), 4-methylaminoantipyrine (MAA), and 4-aminoantipyrine (AA), after intravenous (i.v., intramuscular (i.m.), and oral (p.o.) administration in cats. Six healthy mixed-breed cats were administered MET (25 mg/kg) by i.v., i.m., or p.o. routes in a crossover design. Adverse clinical signs, namely salivation and vomiting, were detected in all groups (i.v. 67%, i.m. 34%, and p.o. 15%). The mean maximal plasma concentration of MAA for i.v., i.m., and p.o. administrations was 148.63 ± 106.64, 18.74 ± 4.97, and 20.59 ± 15.29 μg/ml, respectively, with about 7 hr of half-life in all routes. Among the administration routes, the area under the plasma concentration curve (AUC) value was the lowest after i.m. administration and the AUC . ratio was higher in p.o. than the i.m. administration without statistical significance. The plasma concentration of AA was detectable up to 24 hr, and the mean plasma concentrations were smaller than MAA. The present results suggest that MET is converted into the active metabolites in cats as in humans. Further pharmacodynamics and safety studies should be performed before any clinical use.