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Sulphonamides
- 1. CONTENTS:- 1.INTRODUCTION. 2.CLASSIFICATION. 3.MECHANISM OF ACTIONS. 5.PHARMACOKINETICS/METABOLISM. 7.USES. 8.ADVERSE EFFECTS. BY:- MALLADI.ABHIRAM B.PHARMACY.
- 2. The term sulphonamides are employed as a generic name for the derivatives of para amino benzene sulphonamide (sulphanilamide). The sulphonamide drugs were the 鍖rst effective chemotherapeutic agents to be employed systemically for the prevention and treatment of bacterial infections in humans. The sulphonamides are bacteriostatic antibiotics with a wide spectrum action against most gram-positive bacteria and many gram-negative organisms. Actually it was found to be the metabolic product of Prontosil, which is responsible for antibacterial activity, and this has given the initiation to develop sulphonamides as antibacterial agents.
- 3. S.NO CLASS DRUGS 1. SHORT ACTING SULPHAMETHIZINE SULPHAMETHIZOLE SULFAISOXAZOLE SULPHA DIAZINE SULPASOMIDINE 2. INTERMIDEIATE ACTING SULPHAMETHOXAZOLE SULPHASOMIZOLE 3. LONG ACTING SULPHAMETHOXY PYRIDINE SULPHAMETHOXY DIAZINE SULFPHENAZOLE SULPHA DIMETHXINE 4. SPECIAL PURPOSE MEFENIDE SILVER SULFADIAZINE SULFA ACETAMIDE 5. FOLATE REDUCTASE INHIBITORS TRIMETHOPRIM CLOTRIMAOXAZOLE 6. OTHERS DAPSONE
- 4. Mechanism of action of sulphonamides:- P-amino benzoic acid (PABA) + ptreidine SULPHONAMIDES Dihydropterate synthase Dihyrofolic acid Dihydrofiate TRIMETHOPRIM d reductase Tetrahydrofolic acid Thymidine purine methionine Precursors for DNA&RNA synthesis Competitively antagonism the bacterial dehydrate derivative enzyme & inhibits the folic acid Inhibits the reduction of folic acid through inhibition of dihydrofiate reeducates enzyme thus inhibits the synthesis of DNA
- 5. PHARMACOKINETICS:- It is the prototype of the general purpose sulfonamides that is rapidly absorbed orally&rapidly excreted in urine. Plasma protein binding is 50% and it is 20-40% acetylated. The acetylated derivatives is less soluble in urine,crystalluria is likely. It has good penetrability in brain & CSF. It was the preferred compound for MENINGITIES. Dose :-0.5g QID to 2g TDS. SULFADIAZINE 0.45g tab. SULPHADIAZINE
- 6. SULFAMETHOXAZOLE PHARMACOKINETICS :- It has slower oral absorption and urinary excretion resulting in intermidiate duration of action t1/2 in adults averages 10hrs. It is the preferred compound for combining with trimethoprim because the t1/2 of both is similar. However a high fraction is acetylated, which is relatively insoluble so that crystalluria can occur. Dose : 1g BD for 2 days, then 0.5g BD. GANTANOL 0.5g tab.
- 7. SULFAMETHOPYRAZINE PHARMACOKINETICS :- These are ultra strong acting compounds action lasting >1 week because of high plasma protein binding and slow renal excretion t1/2 is about 5-9 days . They attain low plasma concentration and are not suitable for treatment of acute phylogenic infections But, they are used in combination with pyrimethamine in the treatment of malaria . Large scale use of combination for prophylaxis of malaria is not recommended .
- 8. SULFACETAMIDE PHARMACOKINETICS :- It is a highly soluble compound yielding neutral solution which is only mildly irritating to the eye in concentrations upto 30% It is used typical sulfonamides, because( CH 2-) bridge separates the benzene ring and the amino group. It is used only topically which inhibits a variety of gram +ve & gram ve bacteria. In contrast to typical sulfonamides, it is active in the presence of pus and against the Pseudomonas, clostridia which are not inhibited by typical sulfonamides. It has been mainly employed for burn dressing to prevent infection, but not to treat already infected cases.
- 9. COTRIMOXAZOLE PHARMACOKINETICS :- The fixed dose combination of trimethoprim and Sulphamethoxazole is called cotrimaxozole. Sulphamethoxazole was selected for combining with trimethoprim because both have nearly the same t/ (approx hr) Trimethoprim adquately crosses the BBB and placenta , while Sulphamethoxazole has a poorer entry. Moreover treimethoprim is more rapidly absorbed than Sulphamethoxazole. Trimethoprim is 40% plasma protein bounded while Sulphamethoxazole is 65% bound. Treimethoprim is partly metabolizes in liver and excreted in urine.
- 10. CELL WALL CELL MEMBRANE ERGOSTEROL ERGOSTEROL LANOSTEROL CYTOCHROME P450 CONVERSTION OF LANOSTEROL TO ERGOSTEROL 14-留 Demethylase BINDS
- 11. iInhibits the methylation of lanosterol Blocking the synthesis of Ergosterol Accumulation of 14-留 demethylase Depletion of ergosterol in cell membrane Cell membrane breaks down Fungal organism will die Cytochrome P 450 14-留 Demethylase BINDS AZOLES
- 12. USES :- Systemic use of sulfonamides alone is rare now. Thought they can be employed for suppressive therapy of chronic urinary tract infections. Combined with trimethoprim Sulphamethoxazole is used for many bacterial infections ,P. jioveci and nocardiosis. Ocular sulfacetamide sod. (10-30%) is a cheap alternative in trachoma/ inclusion conjuctivities, though additional systemic azithromycin or tetracycline therapy is equired for eradication of the disease. Topical silver sulfadiazine or mafenide are used for preventing infection on burn surfaces.
- 13. ADVERSE EFFECTS :- Nausea,vomiting and epigastric pain. Crystalluria is dose related ,but infrequent. Hypersensitivity reactions occur in 2-5% patients. These are mostly forms of rashes drug fever. Hepatitis, unrelated to dose, in 0.1% patients. Topical use of sulphinamides is not allowed , risk of contact sensitization . However ocular use is permitted. Hemolysis can occur in G-6PD deficient individuals with high doses of sulfonamides .