Pharmacological properties : תכונות פרמקולוגיות

Pharmacodynamic Properties

5.1     Pharmacodynamic properties

Pharmacotherapeutic classification (Group + ATC code): Analgesic and Antipyretic: S0ZDA03.
Phenazone has analgesic and antipyretic properties. Topically, solutions containing 5% of phenazone have been used locally as ear drops in disorders such as otitis media because of its local anti-inflammatory and analgesic action. Glycerol softens wax.
Tetracaine hydrochloride is used as a local anaesthetic which acts by reversibly blocking the propagation and conduction of nerve impulses along nerve axons. Tetracaine stabilises the nerve membrane, preventing the increase in sodium permeability necessary for the production of an action potential.

Pharmacokinetic Properties

5.2     Pharmacokinetic properties

Phenazone is readily absorbed from the gastro-intestinal tract and is distributed throughout the body fluids. Peak plasma concentrations are usually obtained in 1 to 2 hours. Less than 10% is bound to plasma proteins and it has a half-life of about 12 hours. Phenazone is metabolised in the liver, about 30% to 40% is metabolised to 4-hydroxyphenazone which is excreted in the urine as the glucuronide. Approximately 5% is excreted unchanged and approximately 6% is norphenazone in the urine.
Tetracaine is a weak base (pKa 8.5), therefore, significant changes in the rate of ionised lipid soluble drug uptake may occur with changes in the acid base balance.
The primary site of metabolism for Tetracaine is the plasma.
Pseudocholinesterases in the plasma hydrolyse Tetracaine to 4-aminobenzoic acid. Unmetabolised drug is excreted in the urine.