Antibiotic sulphonamides and potientiate sulpha history,classification,mechanism of action and adverse effect

1. AMIR SOHAIL
SULPHONAMIDES

2. I. Classification and chemistry
II. Mechanism of action
III. Antimicrobial effects
IV. Resistance
V. Pharmacokinetics
VI. Clinical uses
VII. Adverse effects

3. SULPHONAMIDES
History
 Domagk 1935
 Prontosil an azo dye
 Effective against streptococcal infection in mice
 Noble prize in medicine 1938
 Release of an active metabolite The Sulphanilamide
 First synthesized for antibacterial use in the market
 Many developed for use in human and veterinary
medicines.

4. SULPHONAMIDES
 Structure. The sulfonamides are derivatives of p-
aminobenzene sulfonic acid and are structurally
similar to p-aminobenzoic acid (PABA), an
intermediate in the bacterial synthesis of folic acid.
Characteristics. The sulfonamides behave as weak
organic acids, which are poorly water-soluble unless
prepared as sodium salts.
a. Concentrated solutions of the sodium salts of
most sulfonamides are alkaline (pH 9-10) and may
be corrosive.

5. c. Sulphas have low water solubility and in body
they are more or less acetylated & become
more or less soluble in water, but acetyl
sulphadiazine is more insoluble and form
crystalluria.
d. Highly soluble Sulphas are retained in lumen
of GIT for prolonged periods & are called “gut
active Sulphas”
e. Sulphas are white crystalline powders,
insoluble in water, form salts with strong acids
or basis.

6. Chemistry of Sulfonamides
 Sulphonamide nucleus possesses two amino groups
(N1, N4).
 Members differ in N1 substitution for solubility,
potency and pharmacokinetics
 Presence of para-amino group(N4) is essential for
antibacterial activity

7. Chemistry of Sulfonamides
1
4

8. Classification of Sulfonamides
1. Oral, absorbable;
① Short-acting (＜12 hours)
sulfisoxazole (SIZ).
② Medium-acting (12～24 hours)
sulfamethoxazole (SMZ);
sulfadiazine (SDZ).
③ Long-acting (＞24 hours)
sulfadoxine,

9. Classification of Sulfonamides
2. Oral, nonabsorbable;
Sulfasalazine,
3. Topical;
Sodium sulfacetamide ophthalmic
solution or ointment,
Mafenide acetate,
Silver sulfadiazine, SD-Ag;

10. CLASSIFICATION
Into several types, based mainly on indications and
duration of action in body: (Generic Names)
A. Rapidly Absorbed & Rapidly Excreted Sulphas:
 Sulphadiazine, Sulphapyridine, Sulphathiazole,
Sulphamerazine, Sulphamethazine,
Sulphamethoxazole
B. Rapidly Absorbed & Slowly Excreted Sulphas:
 Sulphamethoxypyridazine Sulphadimethoxine,
Sulphamethoxydiazine, Sulphaethoxypyridazine
C. Poorly Absorbed (Enteric) Sulphas:
 Sulphaguinidine
 Succinylsulphathiazole

11. D. Special Purpose Sulphas
 Sulphaisoxazole (Urinary infection)
 Sulphacetamide (Eye infection)
E. Potentiated Sulphas:
Sulphas are used in combination with pyrimethamine
to treat protozoal diseases like Leishmaniasis &
Toxoplasmosis e.g
 Sulphamethoxazole+TMP= Septran
 Sulphadiazine+TMP= Tribrissen
TMP= Trimethoprim

12.  Depending on their type and duration
 I. Systemically acting sulphonamides.
1. Short acting (Duration less than 12 hours)
2. Intermediate acting ( Duration 12-24 Hours)
3. Long acting (Duration 24-48 hours)
4. Ultra long acting (Duration more than 48 hours)
II. Locally acting Sulphonamides.
1. Gut-acting (Sulphaguinidine, Succinylsulphathiazole, Sulphasalazine)
2. Topically acting (Sulphacetamide, Mafenide, SD-Ag)

13. Mechanism of action
Sulfonamides are structural analogs of
PABA that competitively inhibit
dihydropteroate synthase. Drugs inhibit
growth by reversibly blocking folic acid
synthesis.

15. Inhibition of tetrahydrofolate synthesis
by sulfonamides and trimethoprim.

16. Antimicrobial effects
① Broad spectrum
Both G+ & G- bacteria, nocardia,
chlamydia trachomatis, some
protozoa, some enteric bacteria (E coli,
klebsiella, salmonella, shigella, &
enterobacter)
Sulfonamides stimulate rickettsiae in
their growth.

17. Antimicrobial Spectrum:
 Against G+ and G- bacteria
 Broad Spectrum
Sensitive organisms are:
 Streptococci
 Staphylococci
 Corynebacterium
 E. coli
 Salmonella
 Klebsiella
 Pasteurella etc.

18. Antimicrobial effects
② Bacteriostatic drugs
③ Mechanism of action
Susceptible bacteria require
extracellular PABA in order to form
dihydrofolic acid, an essential step in
the production of purines and the
synthesis of nucleic acids.

19. Resistant Strains:
 Mycobacterium tuberculosis, typhoid and
paratyphoid bacilli etc.
Resistance can be avoided by:
 Stopping unjustified use
 Initiate therapy early
 Establish and maintain bacteriostatic conc. of drug in
host.

20. Resistance to Sulfonamides
① Over-production of PABA;
② Produce dihydropteroate synthase
with low sulfonamide affinity;
③ Loss permeability to the sulfonamide;
④ Use exogenous sources of folate;
By mutations or encoded on a
plasmid, cross-resistances,

21. Pharmacokinetics
① Oral administration, absorbed well,
② Distributed widely to tissues and
body fluids, including CNS and
cerebrospinal fluid, placenta, and
fetus; 20-90% protein binding rate;
③ Acetylated or glucuronidated in the
liver,

22. Pharmacokinetics
④ Sulfonamides and inactive
metabolites are excreted into the
urine, they are more soluble at
alkaline than at acid pH. In renal
failure patient, drug dose must be
reduced.

23. PHARMACOKINETICS
Absorption: PO, IV, IP, IM, IU or topically.
Distribution: throughout body tissues.
Biotransformation: extensively metabolized. The
acetylated, hydroxylated & conjugated forms have
a little antibacterial activity.
Acetylation reduces the solubility of most Sulphas.
Hydroxylated & conjugated forms are less likely to
precipitate in urine.
Excretion: Excreted in urine, bile, feces, milk, sweat
etc.

24. Administration and fate of the sulfonamides

25. Clinical uses of Sulfonamides
① SMZ+TMP (Co-trimoxazole)
a. Treatment of urinary tract infections
b. Respiratory tract infections, sinusitis,
bronchitis, pneumonia, otitis media,
and dysentery,
② SDZ+TMP (Tribrissen)
First-line therapy for treatment of acute
toxoplasmosis
sulfamethoxazole (SMZ)
sulfadiazine (SDZ).

26. Clinical uses of Sulfonamides
3. Sulfadoxine+TMP (Trivertin)
Used as a second-line agent in treatment for malaria.
4. Sulfasalazine
widely used in ulcerative colitis, enteritis, and other
inflammatory bowel disease.
Sulfapyridine (antibacterial)
Sulfasalazine is split by intestinal microflora
5-aminosalicylate (5-ASA)
(anti-inflammatory)

27. Clinical uses of Sulfonamides
5. Sodium sulfacetamide (SA-Na)
Bacterial conjunctivitis
6. Mafenide acetate
Prevent bacterial colonization and infection of burn
wounds,
7. Silver sulfadiazine
For prevention of infection of burn wounds

28. Adverse effects of Sulfonamides
1. Allergenic reactions
All sulfonamides and their derivatives,
including carbonic anhydrase
inhibitors, thiazides, furosemide,
bumetanide, torsemide, diazoxide,
and the sulfonylurea hypoglycemic
agents are cross- allergnic.

29. Adverse effects of Sulfonamides
The most common adverse effects are
fever, skin rashes, exfoliative dermatitis
or cutaneous eruption , photosensitivity,
urticaria, nausea, vomiting, diarrhea.
Stevens-Johnson syndrome, is a
particularly serious and potentially fatal
type of skin and mucous membrane
eruption associated with sulfonamide use.

30. Sulfonamides
2. Urinary tract disturbances
Sulfonamides may precipitate in urine, especially at
neutral or acid pH, producing crystalluria, hemturia, or
even obstruction.
SD & SMZ, when in large doses, fluid intake is poor, can
cause crystalluria.
Sodium bicarbonate to alkalinize the urine, adequate
fluids,

31. Sulfonamides
3. Hematopoietic disturbances
Hemolytic or aplastic anemia,
granulocytopenia, thrombocytopenia,
or leukemoid reactions.
Provoke hemolytic reactions in
patients whose red cells are deficient
in glucose-6-phosphate
dehydrogenase.

32. SIDE EFFECTS
 Hypersensitivity or direct
toxic effects.
Hypersensitivity includes
urticaria, anaphylaxis, skin
rashes, drug fever, hemolytic
anemia etc.

33. Some adverse reactions to sulfonamides.

34. DRUG INTERACTIONS!
 Antacids tend to inhibit GI absorption of
Sulphas
 Alkalization (sodium lactate, sodium
bicarbonate and sodium citrate) of urine
promotes Sulphas excretion and urinary
acidification increases risk of crystalluria.

35. Renal Toxicity:
 Sulphanilamide and Sulphathiazole, precipitation of
crystals in collecting tubules of kidney and pelvis
 Obstruction of urine flow
 Injury to tubular epithelium or epithelial lining
Precipitation occurs due to
1. Solubility of drug in urine is low
2. pH of urine is low
3. Concentration of drug in urine is high

36.  As weak organic acids, sulphas are more soluble in
alkaline than acidic solutions
Urinary precipitation of sulphas can be checked by
 Use drugs of high urine solubility
 Increase pH of urine (Sodium lactate, sodium
bicarbonate or sodium citrate)

37. Contraindication for sulfonamide
treatment.

38. Formation of formaldehyde from methenamine at
acid pH.

39.  Sulphonamide react with formaldehyde,and must not
be used concomitantly with methenamine.

40. POTENTIATED SULPHAS

41.  Group of Diaminopyrimidines (Trimethoprim,
Methoprim, Ormetoprim, Aditoprim,
Pyrimethamine etc.)
 Inhibit dihydrofolate reductase in bacteria and
protozoa
 Bactericidal activity with sulphas
 Basic drugs, accumulate in acidic media as urine,
milk
Examples of Potentiated sulphas:
1. Sulphadiazine+TMP
2. Sulphamethoxazole+TMP
3. Sulphadoxine+TMP
4. Sulphadimethoxine+Ormetoprim

42. Combination of Sulphas with Trimethoprim (TMP)
 Effectiveness of Sulphas can be improved by
combining them with inhibitors of bacterial
dihydrofolate reductase like trimethoprim (TMP).
 TRIMETHOPRIM (TMP)
1. Decreases amount of sulpha
2. Increases therapeutic index
3. Widens antibacterial spectrum

43. Synergism between trimethoprim and sulfamethoxazole on the inhibition
of growth of Escherichia coli.

44.  The action of combinations is bactericidal and are
effective against
Actinomyces, Bacillus anthracis, Brucella, Clostridium,
Corynebacterium, E. coli, Haemophilus, Klebsiella,
Proteus, Salmonella, Staph, Strepto, Vibrio etc.

45. Administration and fate of the cotrimoxazole.

46. Mechanism of Action of Trimethoprim
Dihydrofolic acid reductases inhibitor
Dihydrofolic acid reductases convert
dihydrofolic acid to tetrahydrofolic
acid, a step leading to the synthesis
of purines and ultimately to DNA.

47. Trimethoprim
It Inhibits bacterial dihydrofolic acid
reductase about 50000 times more
efficiently than the same enzyme of
mammalian cells. Pyrimethamine,
inhibits the activity of dihydrofolic acid
reductase of protozoa more than that
of mammalian cells.

48. Sulfonamides & Trimethoprim
They produce sequential blocking in
this metabolic sequence, resulting in
marked enhancement of the activity of
both drugs. The combination often is
bactericidal, compared to the
bacteriostatic activity of a sulfonamide
alone.

49. Inhibition of tetrahydrofolate synthesis
by sulfonamides and trimethoprim.

50. Resistance to trimethoprim
Resistance to trimethoprim
 Reduced cell permeability
 Overproduction of dihydrofolate
reductase,
 Production of an altered reductase
with reduced drug binding
By mutation, plasmid-encoded,

51. Pharmacokinetics of Trimethoprim
Given orally, absorbed well.
Distributed widely in body fluids and tissues, including
cerebrospinal fluid, 65-70% protein-bound.
TMP 50-60% excreted in the urine within 24 hours.
TMP concentrates in prostatic fluid and in vaginal fluid, it
has more effects than many other drugs.
TMP∶SMZ=1∶5, they have similar half-life

52. Clinical uses of Trimethoprim
Oral TMP
alone in acute urinary tract infections
Oral TMP+SMZ
① P carinii pneumonia, shigellosis,
systemic salmonella infections
caused by ampicillin- or
chloramphenicol-resistant bacteria,

53. ② Complicated urinary tract infections, prostatitis, some
nontuberculous mycobacterial infections
③ Many respiratory tract pathogens
TMP+SMZ (IV)
① The agent of choice for moderately severe to severe
pneumocystis pneumonia, such as in AIDS patients

54. ② Used for G- bacterial sepsis, including
that caused by some multiple-drug-
resistant species such as
enterobacter and serratia, shigellosis,
typhoid fever, or urinary tract
infection.

55. Typical therapeutic applications of co-trimoxazole
(sulfamethoxazole plus trimethoprim).

56. Oral Pyrimethamine + SN
① Leishmaniasis
② Toxoplasmosis
③ Falciparum malaria

57. Adverse effects of Trimethoprim
① Hematologic toxicity
Megaloblastic anemia, leukopenia,
and granulocytopenia
② Nausea and vomiting, drug fever,
vasculitis, renal damage, and CNS
disturbances

58. Some adverse reactions to cotrimoxazole.

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