C.11 antifolate drugs

Question 1

which drugs are included in this group??

Answer 1

Drugs include sulfonamides, trimethoprim and pyrimethamine

Sulfonamides inhibit the formation of dihydropteroic acid (inhibit dihydropteroate synthease) – not found in humans!

and trimethoprim+pyrimethamine inhibit the formation of tetrahydrofolic acid (inhibit dihydrofolate reductase).— found in humans (also anticancer drug).

Question 2

Sulfonamide
Spectrum
Static or Cidic?
Mechanism:

Answer 2

Gram positive and negative bacteria including:
Nocardia, chlamydia trachomatis,
Some protozoons
Enteric bacteria

Bacteriostatic DRUG!

Sulfonamides inhibit the formation of dihydropteroic acid (inhibit dihydropteroate synthease) – not found in humans!

Question 3

Sulfonamide absorption

Answer 3

Oral absorable:
sulfamethoxazole and sulfadiazine (medium acting) and sulfadoxine (long acting)

Non absorbable
Sulfasalzine

Topical Agents
Silver sulfadiazine which is used in burns
Sulfadimine

Question 4

where is sulfasalazine used really unrelated to bacteria?

Answer 4

RA and Ulcerative colitis

Question 5

Kinetics:

Answer 5

good absoprtion from GI with entry to CNS placenta and fetus (which is why its contraindicated in babies).

High protein binding!–> drug interactions!

Metabolized in liver and excreted in urine.

Uses in topical or oral use.

Question 6

Adverse affects of sulfonamides

Contraindicated!?

Answer 6

Hypersensitivity (Stenven johnson, rash), 
Hemolysis in G6pd patients
Photosensitivity.
GI effects
Nephrotoxic 
Urine crystals and hematuria
and  hematoxcitiy.

Question 7

sulfonamide drugs!

Answer 7

Oral absorable:
sulfamethoxazole and sulfadiazine (medium acting) and sulfadoxine (long acting)

Non absorbable
Sulfasalzine

Topical Agents
Silver sulfadiazine which is used in burns
Sulfadimine

Question 8

Why combine trimethoprim and sulfamethoxazole?!
Static or cidic?
What is the name of the combo drug?
Clinical use

Adverse effect (Common).

Answer 8

Synergy and reduced resistance.
Static drug
Cotrimoxazole

Clinical use:
Pneumocystitis jiroveci, toxoplasma, nocardiosis
Shigella enteritis and some salmonlla infections
UTI

Can cause bone marrow supression

Question 9

Pyrmethamine and sulfamethoxaole/ sulfadoxin / sulfadiazine

Answer 9

indications: Leishmania, toxoplasma Falciparum

Oral and parental use