Anti bacterial drugs cell wall synthesis inhibitors 2

Question 1

discuss the characteristics of Cephalosporins

Answer 1

They are similar to penicillin but are more stable to many bacterial beta lactamase and thus have a broader activity spectrum.

They are semi synthetic antibiotics

Question 2

Which bacteria is resistant to all cephalosporins

Answer 2

Enterococci

Question 3

Cephalosporin general rules

Answer 3

First generation is most effective against against gram positive

Fourth generation is similar to first generation and effective against gram negative

through chemical modification of the basic cephalosporins structure ,there is an increase in effectiveness of suceeding generations against gram neg aerobic organisms

Question 4

How do bacteria develop resistance ?

Answer 4

1. No cell wall
2. Decreased permeability
3. Bacteria do not grow
4. Alterations in binding proteins
5. β-Lactamase production

Question 5

The pharmacokinetics of cephalosporins

Answer 5

Variable T1/2
• Ceftriaxone → 40% hepatic elimination
• Excretion → via kidney (can use probenecid to
increase t1/2 except ceftriaxone) (Drugs that block tubular secretion eg probenecid may increase serum levels ,thats why patients with impaired renal functions must be given i small doses
• Third generation → Penetrates well into CSF

Question 6

Cephalosporins side effects

Answer 6

1. Hypersensitivity reaction (anaphylatic shock ,fever ,skin rash ,nephritis ,granulocytopenia and hemolytiv anemia

Question 7

Cephalosporins side effects

Answer 7

1. Hypersensitivity reaction (anaphylatic shock ,fever ,skin rash ,nephritis ,granulocytopenia and hemolytiv anemia )
   * .Chemical structure differes enough from penicillin so that some people can tolerate them
   * Occurance of hypersensitivty occurs in 2% of population
2. Some can also cause alcohol intolerance (cefamandole)
3. Effectiveness of combined with contraception
4. Nephrotoxicity ( co- administered with aminoglycosides or vancomycin)
5. Phlebitis can occur via IV
6. Neurotoxicity can occur at high doses

Question 8

How does cephalosporin interact with other substances ?

Answer 8

1. Alcohol ( with some cephalosporins)
2. Warfarin
3. NSAIDs
4. Combined with oral contraceptives pills
5. probenecid
6. Cephalosporins and aminoglycosides in same container may chemically inactivate each other .
7. Ceftriaxone ( not to be administered at the same time as calcium solutions for more than 48 hrs

Question 9

Cautions/Contraindications

Answer 9

1. Anaphylatic shock (PENICILLIN)
2. ALLERGY
3. Ceftriaxone contraindicated in hyperbilirubinemia neonates ( premature infants)

Question 10

What are the characteristics of carbapenems?

Answer 10

They have a broad spectrum ( gram pos and neg anaerobic bacteria

Not active against methicillin resistant staphylococus

Question 11

List the drug examples of Carbapenems

Answer 11

Imipenem + cilastatin (enzyme inhibitor that blocks
renal metabolism)
• Meropenem
• Ertapenem (narrower spectrum)
• Doripenem (withdrawn in Europe)

Question 12

What is the mechanism of action of carbapenems?

Answer 12

Bactericidal , same as penicillin

Question 13

Uses of carbapenems

Answer 13

1. Imipenem: Severe nosocomial infections ( septicemia, endocarditis and lower reparatory infection, GUT ,intra-abdominal,bone , skin, joints, and soft tissue infection )
2. Meropenem: Alternative treatment for bacterial meningitis,it can penetrate the CSP
3. Ertapenem : Single dose daily via IV

Question 14

What are the side effects of carbapenems

Answer 14

1.Similar to other beta lactams (hypersensitivity reaction ,GIT effects ,haematological abnormalities ,CNS effects (seizures at high dosages of imipenem)
Increased liver enzymes
Increased serum creatinine and blood urea

2. Red discoloration of urine in children(imipenem)
3. IV : pain ,erythema and thrombophlebitis

Question 15

Cautions and contradictions

Answer 15

1.Allergy
2 CNS disorders or seizures
3.Renal impairment

Question 16

Give an example of monobactams

Answer 16

Aztreonam

Question 17

Give the mechanism of action of monobactams

Answer 17

Bactericidal ,same as penicillin

Question 18

What is the spectrum of monobactams?

Answer 18

Their spectrum is limited to aerobic gram negative bacteria eg E.coli and p. Aeruginosa

Question 19

How are monobactams administered

Answer 19

IV or IM

Question 20

What are the side effects of monobactams?

Answer 20

1. Injection site reaction
2. Rash
3. Rarely toxic epidermal necrolysis
4. Gastrointerstinal side effects
5. Drug induced eosinophilia

Question 21

Give an example of glycoprotein antibiotics

Answer 21

Vancomycin and Teicoplanin and fosfomycin

Question 22

What is the spectrum of vancomycin

Answer 22

1. It is active against gram positive only
2. It is a antibiotic reserved for treatment of life threatening infections
3. It is an alternative treatment for endocarditis (in penicillin allergic patients)

Question 23

Use of vancomycin

Answer 23

Use is restricted to cloxacillin resistant staphylococci and penicillin resistant enterococci

Question 24

How is vancomycin administered

Answer 24

1. In gastrointestinal tract infections (orally) and

2. No cross resistance with other anti biotics

Question 25

Action of mechanism of vancomycin

Answer 25

1. bactericidial 2. Inhibits cell wall synthesis 3. Transglycosylation between side chains thus peptidoglycan cross-linkage does not form resulting in a weakened cell wall , eventually the bacterium lyses

Question 26

Discuss the Pharmacokinetics vancomycin

Answer 26

1. Poorly absorbed when administered orally 2. IM administration is painful 3. The drug is only administered by IV infusion slowly 4. It administered orally for pseudomembranous colitis 5. Half life is 4 to 11 hours 5. Excreted 80-90% unaltered via glomerular filtration in the urine

Question 27

What are the side effects of vancomycin

Answer 27

1. fever and skin rashes 2. When administered rapidly ,it causes histamine release ,causing blushing of the neck and face known as red man syndrom 3. Ototoxic and nephrotoxic ,rare 4. Nephrotoxic in geriatric 5. Therapeutic drugs monitoring essential in elderly , children and impaired renal function

Question 28

Drug interaction of vancomycin

Answer 28

Ototoxic and nephrotoxic drugs eg aminoglycosides

Question 29

Cautions/Contraindications of vancomycin

Answer 29

1. Renal Impairment 2. Elderly patients 3. Neonates/young infants 4. Hearing abnormalities 5. Pregnancy

Question 30

What are the mechanism of action of teicoplanin

Answer 30

- Similar to vancomycin 1. bactericidial 2. Inhibits cell wall synthesis 3. Transglycosylation between side chains thus peptidoglycan cross linkage does not form resulting in a weakened cell walll ,eventually the bacterium lyses

Question 31

Discuss the pharmacokinetics of teicoplanin

Answer 31

1.IM (painful) Usually administered via IV 2.Half life is 45 to 70 hr ,thus give one dose a day

Question 32

what are the side effects of teicoplanin?

Answer 32

Same as vancomycin, lower incidence of “red man” syndrome, allergy (cross sensitivity with vancomycin)

Question 33

what is the spectrum of Fosfomycin

Answer 33

It is active against gram pos and gram neg ( broad spectrum

Question 34

What are the actions of mechanisms for the fosfomycin

Answer 34

1. bactericidal | 2. Inhibits early stages in bacterial cell wall synthesis

Question 35

What causes fosfomycin in resistance in bacteria

Answer 35

Inadequate transport of drug into cell

Question 36

Discuss pharmacokinetics of Fosfomycin

Answer 36

1.when administered orally ,absorption is delayed by food (takes two hours before meal) 2. Excreted in breast milk Excreted in urin (30 to 60%)

Question 37

Uses of Fosfomycin

Answer 37

Uses: 1. Single-dose therapy for acute uncomplicated lower urinary tract infections (sensitive E. Coli) 2. Prophylaxis in diagnostic and surgical transurethral procedures

Question 38

what are the side effects of fosfomycin

Answer 38

GIT disturbances, skin rashes

Question 39

Drug interaction of fosfomycin

Answer 39

Metoclopramide → ↓ serum & urinary | concentrations of fosfomycin (avoid)

Question 40

Cautions/Contraindications of fosfomycin

Answer 40

C/I in renal failure | 2. Caution → pregnancy & lactation