Antipyrine targets the synthesis of prostaglandins and leukotrienes, key mediators of inflammation and pain. By inhibiting these pathways, it exerts analgesic, antipyretic, and anti-inflammatory effects. Its mechanism of action is similar to other pyrazolone derivatives. It also has platelet-inhibitory actions.

In vitro, antipyrine inhibits the synthesis of prostaglandins and leukotrienes. Its effects on these pathways have been demonstrated in cell-free and cellular systems. It also inhibits platelet aggregation. These activities confirm its analgesic and anti-inflammatory properties.

In vivo, antipyrine is used to treat pain, fever, and inflammation. It is an analgesic, antipyretic, and anti-inflammatory agent. Its clinical use has declined with the development of newer analgesics, but it remains a research tool.

The in vitro enzyme assay for antipyrine measures its ability to inhibit prostaglandin and leukotriene synthesis. These cell-free assays use purified enzymes or tissue homogenates and measure the production of prostaglandins or leukotrienes. The compound's inhibitory potency is determined by measuring the reduction in product formation.

In vitro cellular assays for antipyrine assess its effects on prostaglandin and leukotriene production. Cells are treated with antipyrine, and the production of these mediators is measured. Its effects on platelet aggregation can also be assessed. These assays demonstrate the compound's functional activity in a relevant cellular context.

In vivo animal studies for antipyrine have been conducted in animal models of pain, fever, and inflammation to evaluate its efficacy. However, its clinical efficacy has been established in human use.

Metabolism / Metabolites
The known metabolites of antipyrine include norantipyrine, 3-hydroxymethylantipyrine, and 4-hydroxyantipyrine.
Antipyrine is administered orally. It is well-absorbed and distributed throughout the body. It is metabolized in the liver and excreted in urine. Its pharmacokinetic properties are characterized by a relatively long half-life.

Effects During Pregnancy and Lactation
◉ Overview of Use During Lactation
Antipyrine is unlikely to harm the infant. Since antipyrine is only available in the United States as ear drops, it is unlikely to be absorbed by the mother and pass into breast milk. No special precautions are required when the mother uses ear drops containing antipyrine.
◉ Effects on Breastfed Infants
No published information found as of the revision date.
◉ Effects on Breastfeeding and Breast Milk
No published information found as of the revision date.
Antipyrine is generally well-tolerated. Common adverse effects include gastrointestinal disturbances and, rarely, agranulocytosis. Its safety profile is similar to other pyrazolone derivatives. Its use has declined due to the availability of safer alternatives.

[1]. Stevenson, I.H., Factors influencing antipyrine elimination. Br J Clin Pharmacol, 1977. 4(3): p. 261-5.

[2]. Antipyrine as a probe for human oxidative drug metabolism: identification of the cytochrome P450 enzymes catalyzing 4-hydroxyantipyrine, 3-hydroxymethylantipyrine, and norantipyrine formation. Clin Pharmacol Ther. 1996 Jun;59(6):613-23.

Antipyrine is a pyrazolone derivative with the structure 1,2-dihydropyrazol-3-one, where methyl groups are substituted at the N-1 and C-5 positions, and a phenyl group is substituted at the N-2 position. It is a non-narcotic analgesic, antipyretic, nonsteroidal anti-inflammatory drug (NSAID), cyclooxygenase 3 inhibitor, and also an exogenous substance and environmental pollutant. Antipyrine is an analgesic and antipyretic that can be administered orally or as ear drops. It is commonly used to test the effects of other drugs or diseases on hepatic drug-metabolizing enzymes. (Excerpt from Martindale Pharmacopoeia, 30th edition, p. 29) There are reports of the presence of antipyrine in humans, and relevant data exist. Antipyrine is an analgesic and antipyretic that can be administered orally or as ear drops. Antipyrine is commonly used to test the effects of other drugs or diseases on hepatic drug-metabolizing enzymes. (Excerpt from Martindale Pharmacopoeia, 30th Edition, p. 29)
See also: Antipyrine; Benzocaine (component)...View more...
Drug Indications
Antipyrine is an analgesic commonly used to test the effects of other drugs on liver enzymes. When used in combination with benzocaine in an otolytic solution, antipyrine is suitable for relieving symptoms of acute otitis media of various etiologies.
Mechanism of Action
Antipyrine primarily acts on the central nervous system, increasing the pain threshold by inhibiting two isoenzymes of cyclooxygenase (COX-1, COX-2, and COX-3), which are involved in the synthesis of prostaglandins (PGs).
Pharmacodynamics
Antipyrine is an analgesic and antipyretic, administered orally or as ear drops. Antipyrine is commonly used to test the effects of other drugs or diseases on hepatic drug-metabolizing enzymes. (Excerpt from Martindale Pharmacopoeia, 30th Edition, p. 29)
Antipyrine (phenazone) is an anti-inflammatory agent with analgesic, antipyretic, and platelet-inhibitory actions. It was one of the first synthetic analgesics. It works by inhibiting the synthesis of prostaglandins and leukotrienes. It is a research compound and is not widely used clinically.

C11H12N2O

188.2258

188.094

C, 70.19; H, 6.43; N, 14.88; O, 8.50

60-80-0

Antipyrine-d3;65566-62-3

2206

White to light yellow crystalline powder.

1.2±0.1 g/cm3

319.0±0.0 °C at 760 mmHg

109-111 °C(lit.)

114.8±15.0 °C

0.0±0.6 mmHg at 25°C

1.585

0.27

0

2

1

14

267

0

O=C1C([H])=C(C([H])([H])[H])N(C([H])([H])[H])N1C1C([H])=C([H])C([H])=C([H])C=1[H]

VEQOALNAAJBPNY-UHFFFAOYSA-N

InChI=1S/C11H12N2O/c1-9-8-11(14)13(12(9)2)10-6-4-3-5-7-10/h3-8H,1-2H3

1,5-dimethyl-2-phenylpyrazol-3-one

Antipyrine, Phenazone, Azophen, NSC 7945, NSC 7945, NSC 7945, Auralgan

2934.99.9001

Powder      -20°C    3 years

                     4°C     2 years

In solvent   -80°C    6 months

                  -20°C    1 month

Room temperature (This product is stable at ambient temperature for a few days during ordinary shipping and time spent in Customs)

H2O : ≥ 100 mg/mL (~531.26 mM)
DMSO : ~100 mg/mL (~531.26 mM)

Solubility in Formulation 1: ≥ 2.5 mg/mL (13.28 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.

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Solubility in Formulation 2: ≥ 2.5 mg/mL (13.28 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.

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Solubility in Formulation 3: ≥ 2.5 mg/mL (13.28 mM) (saturation unknown) in 10% DMSO + 90% Corn Oil (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 corn oil and mix evenly.

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Solubility in Formulation 4: 110 mg/mL (584.39 mM) in PBS (add these co-solvents sequentially from left to right, and one by one), clear solution; with ultrasonication.

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 (Please use freshly prepared in vivo formulations for optimal results.)