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Sulphonamides Cheomotherapy

Sulphonamides Cheomotherapy - The first antibacterial compounds used were the sulphonamides, the antibacterial properties of the dyestuff, Prontosil rubrum were found to be associated with the sulphonamide group of the compound. The sulphonamides have today largely been replaced by the antibiotics. The-main reasons for this, are: (i) antibiotics have greater potency, and, (ii) several strains of bacteria have acquired resistance to sulphonamides.

Some of the compounds, however, ate still in use.Sulphonamides are derivatives of para-aminobenzene sulphomide. A large number of derivatives have been prepared by substituting the hydrogen atoms of the amino radicals with other groups. The sulpho­namides-are bacteriostatic rather than bactericidal. Their value lies in their ability to slow down or prevent bacterial multiplication in a wound or infected system with out appreciable toxicity to the body tissues. They are useful in treatment of infections caused by staphy­lococci, streptococci, meningococci and urinary infections caused by gram negative bacteria. However, organisms develop resistance to sulphonamides in the course of therapeutic use.

The sulphonamides inhibit bacterial growth by interfering with the action of Para aminobenzoic acid (PABA). The structure of sulphonamides closely resembles that of PABA. PABA is one of the important constituents of the vitamin folic acid. Folic acid coenzymes ace essential for various metabolic reactions. Sulphanilamide competes with PABA for a position in the folic acid molecule.Thus enzymic functions dependent upon folic acids are stopped in the presence of sulphanilamide.

In synergistic combined therapy the effectiveness of sulphona­mides is increased by adding the folic-acid antagonist trimethoprim. Simultaneous partial inhibition of two steps in a metabolic pathway multiplies the two degrees of inhibition (synergistic action).

Diaminodiphenyl sulphone (dapsone) is specifically used in the treatment of leprosy. Although it does not have a su1plionamide group, this drug was synthesized as a congener of sulphanilamide.

P-Aminosalicylic acid (PAS), an analogue of PABA, is useful in the treatment of tuberculosis.

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