Pharmacological properties : תכונות פרמקולוגיות

Pharmacodynamic Properties

5.1   Pharmacodynamic Properties
Lidocaine is a local anaesthetic, of the amide type, the effects of which are reversible.
Lidocaine is also a Class 1A antiarrhythmic agent. It acts by preventing generation and transmission of impulses along nerve fibres and at nerve endings. It blocks nerve conduction by decreasing or preventing the large transient increase in the permeability of the cell membrane to sodium ions which is produced by a slight depolarisation of the membrane. The main site of action is the cell membrane. The local anaesthetic properties of lidocaine therefore form the basis for the use of STUD 100 in reducing tactile sensitivity of the penis.

Pharmacokinetic Properties

5.2   Pharmacokinetic Properties

Lidocaine is readily absorbed from the gastrointestinal tract, from mucous membranes, and through damaged skin. Lidocaine is rapidly distributed into the heart, brain, kidneys and other tissues with a high blood flow. It diffuses across the placenta a few minutes after injection.

Lidocaine undergoes first-pass metabolism in the liver and bioavailability is low after administration by mouth. It is rapidly de-ethylated to the active metabolite monoethylglycinexylidide and then hydrolysed by amidases to various compounds, including glycinexylidide which has reduced activity but a longer elimination half-life and may accumulate to potentially toxic concentrations. Less than 10% of a dose is excreted unchanged via the kidneys. The metabolic products are excreted in the urine.

Systemic availability of lidocaine is low following application to intact skin. After application of STUD 100 to the penis at the maximum recommended dose, plasma lidocaine levels were in the region of 0.2g/ml with peak concentrations attained 1-2 hours after application.