4-Methylamino antipyrine is a bioactive metabolite of Metamizole. Metamizole is a pyrazolone nonsteroidal anti~inflammatory agent (NSAID) that can inhibit COX. Metamizole is a non-opioid compound studied for pain and fever.

Physicochemical Properties

Molecular Formula	C₁₂H₁₅N₃O
Molecular Weight	217.27
Exact Mass	217.121
CAS #	519-98-2
Related CAS #	4-Methylamino antipyrine hydrochloride;856307-27-2
PubChem CID	10618
Appearance	Light yellow to yellow solid powder
Density	1.2±0.1 g/cm3
Boiling Point	324.5±45.0 °C at 760 mmHg
Melting Point	50-53ºC
Flash Point	150.0±28.7 °C
Vapour Pressure	0.0±0.7 mmHg at 25°C
Index of Refraction	1.619
LogP	0.02
Hydrogen Bond Donor Count	1
Hydrogen Bond Acceptor Count	3
Rotatable Bond Count	2
Heavy Atom Count	16
Complexity	318
Defined Atom Stereocenter Count	0
InChi Key	JILCEWWZTBBOFS-UHFFFAOYSA-N
InChi Code	InChI=1S/C12H15N3O/c1-9-11(13-2)12(16)15(14(9)3)10-7-5-4-6-8-10/h4-8,13H,1-3H3
Chemical Name	1,5-dimethyl-4-(methylamino)-2-phenylpyrazol-3-one
Synonyms	4Methylamino antipyrine; 4 Methylamino antipyrine
HS Tariff Code	2934.99.9001
Storage	Powder-20°C 3 years 4°C 2 years In solvent -80°C 6 months -20°C 1 month
Shipping Condition	Room temperature (This product is stable at ambient temperature for a few days during ordinary shipping and time spent in Customs)

Biological Activity

ln Vitro	In an oxygenated environment and at ambient temperature, the prodrug methimizole spontaneously and non-enzymatically transforms into 4-methylaminoantipyrine. In order to produce 4-formamidoantipyrine, which is then transformed into 4-aminoantipyrine, the N-methyl side chain of 4-methylaminoantipyrine is oxidized. The most significant pyrazolone derivative in terms of pharmacology is 4-methylaminoantipyrine, which is part of the group of compounds known as metamizole when present in an aqueous solution and with oxygen [2].
ln Vivo	This study looked at the pharmacokinetics of 4-methylaminoantipyrine, the drug's active metabolite, following a single intramuscular injection of metamizole in male piglets. Metamizole (100 mg/kg) was given intramuscularly into eight healthy male piglets. 4- Quantitative measurements of methylaminoantipyrine plasma concentrations can be made in 0.25 to 48 hours. The 4-methylaminoantipyrine mean maximum concentration was 47.59 mg/mL. 4-methylaminoantipyrine has an average half-life of 8.57 hours [1].
References	[1]. Pharmacokinetic investigations of the marker active metabolites 4-methylamino-antipyrine and 4-amino-antipyrine after intramuscular injection of metamizole in healthy piglets. J Vet Pharmacol Ther. 2016 Dec;39(6):616-620. [2]. Regulation of cyclooxygenase activity by metamizol. Eur J Pharmacol. 1999 Aug 13;378(3):339-47. [3]. Pyrazolones metabolites are relevant for identifying selective anaphylaxis to metamizole. Sci Rep. 2016 Mar 31;6:23845.
Additional Infomation	4-(methylamino)antipyrine is a member of the class of pyrazoles that is antipyrine substituted at C-4 by a methylamino group. It is a metabolite of aminopyrine and of metamizole. It has a role as a non-narcotic analgesic, an opioid analgesic, a non-steroidal anti-inflammatory drug, an EC 1.14.99.1 (prostaglandin-endoperoxide synthase) inhibitor, a peripheral nervous system drug, an antipyretic and a drug metabolite. It is a member of pyrazoles and a secondary amino compound. It is functionally related to an antipyrine. Noramidopyrine has been reported in Euglena gracilis with data available.

Solubility Data

Solubility (In Vitro)

DMSO : ~50 mg/mL (~230.13 mM)

Solubility (In Vivo)

Solubility in Formulation 1: ≥ 2.5 mg/mL (11.51 mM) (saturation unknown) in 10% DMSO + 40% PEG300 + 5% Tween80 + 45% Saline (add these co-solvents sequentially from left to right, and one by one), clear solution. For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 25.0 mg/mL clear DMSO stock solution to 400 μL PEG300 and mix evenly; then add 50 μL Tween-80 to the above solution and mix evenly; then add 450 μL normal saline to adjust the volume to 1 mL. Preparation of saline: Dissolve 0.9 g of sodium chloride in 100 mL ddH₂ O to obtain a clear solution. Solubility in Formulation 2: ≥ 2.5 mg/mL (11.51 mM) (saturation unknown) in 10% DMSO + 90% (20% SBE-β-CD in Saline) (add these co-solvents sequentially from left to right, and one by one), clear solution. For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 25.0 mg/mL clear DMSO stock solution to 900 μL of 20% SBE-β-CD physiological saline solution and mix evenly. Preparation of 20% SBE-β-CD in Saline (4°C，1 week): Dissolve 2 g SBE-β-CD in 10 mL saline to obtain a clear solution.  (Please use freshly prepared in vivo formulations for optimal results.)

Preparing Stock Solutions		1 mg	5 mg	10 mg
	1 mM	4.6026 mL	23.0128 mL	46.0257 mL
	5 mM	0.9205 mL	4.6026 mL	9.2051 mL
	10 mM	0.4603 mL	2.3013 mL	4.6026 mL

*Note: Please select an appropriate solvent for the preparation of stock solution based on your experiment needs. For most products, DMSO can be used for preparing stock solutions (e.g. 5 mM, 10 mM, or 20 mM concentration); some products with high aqueous solubility may be dissolved in water directly. Solubility information is available at the above Solubility Data section. Once the stock solution is prepared, aliquot it to routine usage volumes and store at -20°C or -80°C. Avoid repeated freeze and thaw cycles.