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anti bacterial drugs > Protein synthesis inhibitors > Flashcards

Protein synthesis inhibitors Flashcards

1
Q

Give 10 drugs that are protein synthesis inhibitors

A

Aminoglycosides

  1. Macrolides
  2. Tetracyclines
  3. Chloramphenicol
  4. Clindamycin
  5. Fusidic acid
  6. Mupirocin
  7. Telitromycin
  8. Linezolid
  9. Daptomycin
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2
Q

what is the mechanism of protein synthesis inhibitors

A

Protein synthesis inhibitors target the ribosome that synthesis protein from the mrna code

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3
Q

Give examples of aminoglycosides

A

amikacin ,gentamicin, tobramycin ,netilmicin ‘neomycin ,streptomycin ,kanamycin ,framycetin

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4
Q

What is the spectrum of aminoglycosides

A

they are bactericidal

  • they attack aerobic gram neg infection and some gram pos bacteria
  • they can be used against mycobacterial infection
  • they are polar and crosses the membrane weakly

and not absorbed after oral ingestion

can be used synergistically with penicillin in serious strep enterococci and staph infections

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5
Q

Uses of aminoglycosides

A

serious sight threatening infection

otitis media
infection of the nasal vestibuli

and it is not recommended for skin infections

It is combined with metronidazole or clindamycin for anaerobic infections

low ph in anaerobic cells may inhibit transportation

transport maybe maybe enhanced by cell wall active drugseg penicillin

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6
Q

what is the mechanism of action of aminoglycosides

A
  • penetrates the cell membrane via passive diffusion through porin channels across the outer membrane
  • actively transported across the bacterial membrane into the cytoplasm by an oxygen dependent process where it binds to 30s

they inhibit the protein synthesis pathway by;
*preventing the formation o the initiation complex

  • it breakdown thepolyribosome to non functional monosomes
  • The mrna is incorrectly read and incorrect amino acids are joint to form non functional or toxic proteins
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7
Q

what can lead to aminoglycosides resistance

A
  1. Mutation of binding on 30s ribosomal subunit but on in streptomycin only
  2. Inhibition of transport into cell
  3. Inactivation of enzymes
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8
Q

what is the pharmacokinetics of aminoglycosides

A
  • After IM administration ,it is rapidly absorbed and distributed in the extracellular fluid and tissue
  • half life is 2-3 hrs but it increases in the case of reduced renal capacity and during the use in neonates
  • penetration into the CSF is weak
  • 70-90 % is excreted unaltered within 24 hours in urine

why a single daily dose?
*because the bactericidal effect is concentration dependent and it exert a prolonged post-antibiotic effect

*toxicity depends on critical plasma level and time of exposure
therefore once daily dose is preferable to increase efficacy and decease toxicity

except when used for synergy ( endocarditis)

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9
Q

What are the side effects of aminoglycosides

*NEPHROTOXICITY AND OTOTOXICITY

A

Narrow therapuetic index, thus toxicity is dependent on :

  • plamsa concentration
  • duration of exposure
  • dosage are in accordance with age , body weight and renal function

2.all are nephrotoxic and ototoxic when used for more than 5 days , increased doses in elderly and renal insufficiency

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10
Q

discuss the nephrotoxicity caused by aminoglycoside

A
  • aminoglycosides move into PCT cells via an uptake system for oligopeptides
  • The tubular cells are very sensitive and can be damaged easily
  • neomycin ,tobramycin and gentamicin are most nephrotoxic

*it is generally reversible

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11
Q

discuss the ototoxicity caused by aminoglycosides

A
  • damage to inner ear sensory cells of the vestibular apparatus and organ of corti can bee partly irreversible
  • damage to vesticular results in vertigo ,ataxia and loss of balance
  • cochlear damage can result in deafness
  • neomycin ,kanamycin and amikacin are the most ototoxic
  • strptomycin and gentamicin are most vestibulotoxic

and STREPTOMYCIN GIVEN DURING PREGNANCY CAUSES DEAFNESS IN CHILDREN *OFTEN IRREVERSIABLE

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12
Q

what are the side effects of aminoglycosides

A
  1. neuromuscular blockage ; decreases ACh release by presynaptic neuron and release of sensitivity to ach BY POST SYNAPPTIC NEURON
  2. Electrolyte imbalance
  3. Liver damage
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13
Q

how does aminoglycosides interact with other drugs

A
  1. general anaethetics
  2. Neuromascular blocking agent
  3. 0totoxicity and nephrotoxicity agents
  4. loop diuretics
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14
Q

What are the cautions and contraindications of aminoglycosides

A

1.elderly
2.renal impairment
neonates
pregnancy (streptomycin)
myasthenia gravis

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15
Q

what are the characteristics macrolides

A
  • They are bacteriostatic but they are bactericidal at high doses
  • the prototype macrolides in erythromycin
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16
Q

What is the spectrum of erythromycin

A

(similar to penicillin G)

Macrolides can also be used as an alternative
drug by patients that are allergic to penicillin
• Erythromycin highly active → Corynebacterium
diphtheriae infections
• Erythromycin → acne (2nd line agent)
• Respiratory, neonatal, ocular or genital
chlamydial infections
• Treatment of community-acquired pneumonia
(resistance ↑)

Prophylaxis against endocarditis during dental
procedures (2nd line agent)
• Peptic ulcers (clarithromycin + omeprezole)
• Erythromycin/azithromycin NOT TO BE USED for
syphilis in pregnant women allergic to penicillins
• Azithromycin/clarithromycin → rickettsial
infections (2nd line agent

17
Q

What are the uses of macrolides are effective in treatment of :

A 
Legionnaires disease (Leggionella
pneumophila)
– Whooping cough (Bordetella pertussis)
– Mycoplasma pneumoniae
– Diphtheria (Corynebacterium) infections
18
Q

what is the action of mechanism for macrolides

A
  • attaches to the bacterial 50s robosomal subunit close to the sites for chloramphenicol and clindamycin ( they can competitively inhibit the binding of these agents when given together
  • they inhibit translocation
19
Q

what can cause resistance to macrolides

A
  1. reduced cell membrane permeability or active efflux
  2. production of esterase that hydrolyzes macrolides
  3. modification of ribosomal binding sites
20
Q

discuss the pharmacokinetics of macrolides

A

Erythromycin absorption effected by:
formulation, gastric acidity & food
• Administered orally as stearate salt or esterified
form (estolate)
• Erythromycin (base & stearate) → food ↓
absorption
• Estolate → best absorption
Distributes readily into all tissues, including
prostate fluid
• Crosses the placenta, but not the blood-brain
barrier
• T1/2 → 1.5-2 h (Erythromycin); 3-4
(clarithromycin); 11-14 h (azithromycin)
• High protein binding occurs
• Readily metabolised by the liver and excreted in
the bile
• ± 2 - 5% are excreted unaltered in the urine

21
Q

what are side effects of macrolides

A

1.GIT intolerance (abdominal pain ,cramping ,nausea ,vomitting ,diarrhoea)
2.allergic reaction (rare)
3hepatoxicity
– When the estolate is, however, taken for more
than 10 days, cholestatic jaundice
(irreversible) can occur
– Benign elevation of serum transaminase
4. Erythromycin and clarithromycin → inhibit the
liver cytochrome P450 system & P-glycoprotein

22
Q

how does macrolides interact with other drugs

A

Serum concentrations of different drugs ↑
(e.g. theophylline, and warfarin)
2. Reduce efficacy of combined oral contraceptive
pill

23
Q

what are the Cautions/Contraindications

A

Liver disease
• Impaired biliary function
• C/I Porphyria (erythromycin)
• Heart disease (clarithromycin & azithromycin)

anti bacterial drugs (7 decks)

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