Mechanism of Action
RISUG works by an injection into the vas deferens, the vessel through which the sperm moves before ejaculation. RISUG is similar to vasectomy in that a local anesthetic is administered, an incision is made in the scrotum, and the vas deferens is tugged out with a small pair of forceps. Rather than being cut and cauterized, as it is in a vasectomy, the vas deferens is injected with the polymer gel and pushed back into the scrotum. In a matter of minutes, the injection coats the walls of the vas with a clear gel made of 60 mg of the copolymer styrene/maleic anhydride (SMA) with 120 µl of the solvent dimethyl sulfoxide. The copolymer is made by irradiation of the two monomers with a dose of 0.2 to 0.24 megarad for every 40 g of copolymer and a dose rate of 30 to 40 rad/s. The source of irradiation is cobalt-60 gamma radiation.
The effect the chemical has on sperm is not completely understood. Originally it was thought that it lowered the pH of the environment enough to kill the sperm. More recent research claims that this is not enough to explain the effect.
One explanation is that the polymer is an anhydride, and hydrolizes in the presence of water in the spermatic fluid. Due to the breaking of a cyclic group, the polymer becomes a hydride and has a positive charge. This disturbs the negative charge of the sperm membrane on contact.
Professor SK Guha theorizes that the polymer surface has a negative and positive electric charge mosaic. The differential charge from the gel ruptures the sperm's cell membrane as it passes through the vas, inactivating sperm before they initiate their journey to the egg.
"Within an hour, the drugs produce an electrical charge that nullifies the electrical charge of the spermatozoa, preventing it from penetrating the ovum," Dr. Guha said.
Read more about this topic: Reversible Inhibition Of Sperm Under Guidance
Famous quotes containing the words mechanism of, mechanism and/or action:
“The two elements the traveler first captures in the big city are extrahuman architecture and furious rhythm. Geometry and anguish. At first glance, the rhythm may be confused with gaiety, but when you look more closely at the mechanism of social life and the painful slavery of both men and machines, you see that it is nothing but a kind of typical, empty anguish that makes even crime and gangs forgivable means of escape.”
—Federico García Lorca (1898–1936)
“The law isn’t justice. It’s a very imperfect mechanism. If you press exactly the right buttons and are also lucky, justice may show up in the answer. A mechanism is all the law was ever intended to be.”
—Raymond Chandler (1888–1959)
“The United States must be neutral in fact as well as in name.... We must be impartial in thought as well as in action ... a nation that neither sits in judgment upon others nor is disturbed in her own counsels and which keeps herself fit and free to do what is honest and disinterested and truly serviceable for the peace of the world.”
—Woodrow Wilson (1856–1924)