Pharmacology

1. Sulfonamides
Sulfa drugs

2. Contents
• History
• Mechanism of action
• Classification of Sulfonamides
• Orally absorbable sulfonamides
• Orally non absorbable sulfonamides
• Topical sulfonamides
• Adverse effect
• Drug interactions

4. Mechanism of Action

5. • inhibit enzyme
dihydrofolate reductase
Trimethoprim
• Analogue of trimethoprim
Iclaprim
• inhibit dihudrofolate
reductase ( affinity for
protozoa)
Pyremethamine

6. Antibacteria
effect
overcome
(Resistance)
Excess
formation
of PABA
Presence
of pus

7. Orally Non absorbable agents
Orally absorabable agents

8. Synergistic combination with sulfonamides
sulfamethaxazole Trimethoprim Cotrimoxazole

9. Sulfadoxine Pyrimethamine
Block protozoal folic acid synthesis

10. Antimicrobial Spectrum
Active
• Gram negative
bacilli
• E.coli, shigella,
salmonella
Moderately
active
• Actinomycetes
• Rickettsiea

11. Resistance
Mutation
Overproduction
of PABA
Alteration in
dihydropteroic
acid syntetase
Loss of
permeability of
sulfonamide
Alternative
pathway for
PABA synthesis

12. Pharmacokinetics
• orally
• X IM/SC
• Topical
• IV
Absorption
• Crosses BBB
• Accumulate in prostatic fluid
• Protein binding 85-93 %
Distribution
• Acetylation in liver
Metabolism

13. Clinical Uses
• Rarely used as single agent
• Topical sulfonamides- ulcerative colitis
sulfamethaxazole Trimethoprim Cotrimoxazole

14. Indications of cotrimoxazole
• UTI’s
• Prostatitis
• Respiratory tract infection
• Typhoid
• Bacterial diarrheas and dysentery
• Nocardiosis
• Sexually Transmitted disease
• Pneumonia
• Melioidosis

15. •Toxoplasmosis
Sulfadiazene +
Pyrimethamine
•Malaria
Sulfadoxine +
Pyrimethamine

16. Oral non absorbable sulfonamide
• Drug of choice- Ulcerative Colitis
• Absorb through GIT
• Degaded by Bacterial flora of colon
5-Amino Salicylic acid Sulfapyridine

17. Topical agents
• Trachoma(chlamydia)
• Bacterial conjunctivitis
Sodium
sulfacetamide
• Prevention of infection in burn
cases
• Antimicrobial (Ag+)
Silver
Sulfadiazene
• Burn cases
• Active even in presence of pus
Mafenide

18. Adverse effect
Crystalluria and
renal toxicity
•Less soluble in
acidic urine
•Use of 3 sulfa
drugs
Hypersensitivity
reaction
•Stevens
Johnson
syndrome
•Eosinophllia
Kernictus in
neonates
•Cross BBB
Haemolytic
anaemia
•Deficiency of
glucose-6-
phosphate
dehydrogenase
Cotrimoxazole
fever Hypersensitivity Agranulocytosis

19. Drug Interactions
Sulfonamides
Oral
anticoagulants,
sulfonyl ureas,
Methotrexate