Antibacterial Drugs - Antifolates

Question 1

Sulphonamindes - Drugs

Answer 1

Sodium Sulfacetamide
Silver Sulfadiazine
Sulfamethoxazole

Question 2

Sulphonamindes - MOA

Answer 2

Bacteriostatic
Inhibit production of DNA, RNA and protein by acting as folate antagonists
Compete for dihydropteroate synthetase
Decrease dihydropteroic acid

Question 3

Sulphonamindes - Kinetics

Answer 3

Good GIT absorbtion
Acetylated in liver
pH 2- 7

Question 4

Sulfamethoxazole - Spectrum

Answer 4

UTIs
Respiratory Infxns
Sinusitis 
Pneumonia
Bronchitis

Question 5

Silver Sulfadiazine - Spectrum

Answer 5

Ulcerative colitis
Enteritis and enteric bacteria
IBD

Question 6

Sulphonamindes - Spectrum

Answer 6

Both gram +ve and -ve

Broad spectrum

Question 7

Sulphonamindes - Adverse Effects

Answer 7

Rashes
Renal failure (low pH - crystalluria)
Blood dyscrasias
GIT (nausea, vomiting, anorexia)
Kernicterus (neonates)
Decreased efficacy of COCP

Question 8

Sulphonamindes - C/I

Answer 8

Neonates and Infants
Last trimester of pregancy
Porphyria
G6DP deficiency 
Allergy

Question 9

Sulphonamindes - D/I

Answer 9

Oral anti-coagulants
Sulfonylureas
Phenytoin
Methotrexate (potentiates effects)

Question 10

Sodium Sulfacetamide - Administration

Answer 10

Topical

Question 11

Silver Sulfadiazine - Administration

Answer 11

Topical

Question 12

Sulfamethoxazole - Administration

Answer 12

Oral administration

Question 13

Trimethoprim - MOA

Answer 13

Bacteriostatic
Inhibits dihydrofolate reductase, preventing formation of tetrahydrofolate
NB: Affinity for bacterial enzyme = 50000 x > than human

Question 14

Trimethoprim - Kinetics

Answer 14

Half life: 8 - 11 hours

Excreted unaltered by kidneys

Question 15

Trimethoprim - Spectrum

Answer 15

Broad spectrum
UTIs
RTIs
Chronic Prostatitis

Question 16

Trimethoprim - Adverse effects

Answer 16

Megoblastic anaemia
Leukopaenia
Granulocytosis

Question 17

Trimethoprim - Administration

Answer 17

Oral

Question 18

Co-trimoxazole =

Answer 18

Trimethoprim + Sulfamethoxazole

Question 19

Co-trimoxazole - MOA

Answer 19

Bacteriostatic

Sequential blockade: Synergistic action of trimethoprim & sulfamethoxazole

Question 20

Co-trimoxazole - Spectrum

Answer 20

Broader spectrum than sulphas

Severe RTIs - pneumonia etc

Question 21

Co-trimoxazole - Adverse Effects

Answer 21

Dermatologic hypersensitivity rxns
GIT disturbances (N,V & anorexia)
Haematological disturbances

Question 22

Co-trimoxazole - C/I

Answer 22

HIV/AIDs patients
Elderly (esp. on diuretics)
Anaemics

Question 23

Co-trimoxazole - D/I

Answer 23

Digoxin (↑)
Thiazides (↑ risk of thrombocytopenia) 
COCP (↓ efficacy)
Phenytoin (inhibits metabolism)
Oral anti-diabetic agents (hypoglycaemia)
Pyrimethamine (megaloblastic anaemia)
Rifampicin (↓ levels = ↑ dose)
Warfarin

Question 24

Co-trimoxazole - Administration

Answer 24

Oral