Question | Answer |
Examples of aminoglycosides | Gentamycin.
Streptomycin.
Amikacin.
Tobramycin.
Neomycin.
Netilmicin |
MOA of aminoglycosides | Bind to 30S subunit.
Alter codon:anticodon recognition.
Abnormal protein formed |
Most common use of aminoglycosides | Aerobic G- (some G+).
(Transport through membrane is oxygen dependent) |
Most common aminoglycoside | Gentamycin |
Aminoglycoside used for Pseudomonads | Tobramycin |
When is amikacin used? | For gentamycin or tobramycin resistant strains of bacteria.
When wide spectrum aminoglycosides are needed |
What borders can aminoglycosides cross? | Placenta.
Joints.
Pleura. |
What borders can aminoglycosides not cross? | BBB.
Cells.
Eyes.
Secretions.
Fluids |
What should you beware of when prescribing aminoglycosides | Drug accumulates to toxic levels rapidly during renal failure. |
When should aminoglycosides be d/c'd? | D/c of aminoglycosides can reverse tubule damage. |
What should be looked out for in a patient when prescribing aminoglycosides? | Dehydrated patient.
Other nephrotoxins.
Pre-existing renal failure.
Each of these can exacerbate nephrotoxicity |
What are 3 major S/Es of aminoglycosides? | Nephrotoxicity.
Ototoxicity.
Paralysis. |
What symptoms show in ototoxicity due to all aminoglycosides? | Vertigo.
Ataxia. |
What aminoglycosides cause a loss of balance? | Streptomycin and gentamycin |
What aminoglycosides cause deafness? | Neomycin and amikacin |
How do aminoglycosides cause paralysis? | They create a neuromuscular blockade.
1) They inhibit Ca2+ uptake.
2) This inhibits exocytotic release of ACh |
Examples of tetracyclines | Demecocycline, tetracycline, oxytetracycline, doxycycline, minocycline. |
Are tetracyclines bacteriostatic or bacteriocidal? | Bacteriostatic |
MOA of tetracyclines | They compete with tRNA for A site of 30S subunit of ribosome.
Note - they require active transport into bacterial cells |
Which tetracycline is used for Neisseria Meningitidis? | Minocycline |
Do tetracyclines cross the BBB? | No |
Do tetracyclines have narrow or wide distribution? | Wide.
They are distributed into placenta, breast milk and saliva. |
Clinical uses of tetracyclines? | Rickettsia, mycoplasma, chlamydia, brucellosis, cholera, plague, leptospirosis |
Which tetracycline is used to treat acne? | Minocycline |
Which tetracycline is used to treat SIADH? | Demeclocycline |
What superinfection may be a side effect of tetracycline treatment? | C Difficile superinfection |
To whom should tetracycline be withheld, due to hepatotoxicity? | Children, pregnant women and nursing mothers |
Which tetracycline causes photosensitivity? | Demeclocycline |
Which tetracycline causes vestibular disturbance? | Minocycline |
What is a long term side effect of tetracycline treatment? | Bone marrow suppression |
Name the 30S inhibitors | Aminoglycosides and tetracyclines |
Which drugs does chloramphenicol show competition for? | Erythromycin and clindamycin |
What is the MOA of chloramphenicol? | It inhibits transpeptidation which prevents protein production by the bacterial cell |
Is chloramphenicol considered broad or narrow spectrum? | Broad spectrum.
It covers many G+, G- bacteria and Rickettsia |
Is chloramphenicol bacteriostatic or bacteriocidal? | For most bacteria, chloramphenicol is bacteriostatic. However, it is bacteriocidal for H. Influenza, N. Meningitidis and Strep Pneumoniae |
How is chloramphenicol resisted by bacteria? | Via plasmid mediated production of chloramphenicol acetyl transferase. |
Does chloramphenicol cross the BBB? | Yes. Only 60% of concentration is found in blood |
How is chloramphenicol metabolised? | 90% is metabolised via glucuronidation |
When is chloramphenicol used? | H. Influenza infections (due to resistance to other abx).
Meningitis (when penicillin cannot be used).
Topical eye drops for bacterial conjunctivitis.
±Typhoid fever (other drugs are less toxic) |
What are the major side effects of chloramphenicol? | Bone marrow suppression (dose-dependent) and Grey baby syndrome |
What are some examples of Macrolides? | Erithromycin, Clarithromycin and Azithromycin |
What is their structure? | Multiple lactose rings with deoxy sugars attached |
Are macrolides bacteriostatic or bacteriocidal? | Depends on dose and microorganism |
What drugs are macrolides in competition with? | Chloramphenicol |
Spectrum of activity of erithromycin? | G+, Haemophilus Influenza, Neisseria Gonorrhoea.
(Similar to penicillin so use if allergic) |
Spectrum of activity of azithromycin? | Main action: toxoplasmosis gondii.
(More active than erithromycin for H Influenza and Legionella)
Lyme disease |
Spectrum of activity for clarithromycin | H Influenza, myobacterium avium intracellulare.
Lyme disease |
Do macrolides cross the BBB or placenta? | No to BBB, yes to placenta |
Which macrolide inhibits P450? | Clarithromycin - metabolite |
Which bacteria may be seen with an opportunistic infection of GIT or vagina due to macrolide use? | Candida Albicans |
What class of drugs does clindamycin belong to? | Lincosamides |
What is the MOA of climdamycin? | It inhibits translocation via binding to 50S subunit |
Side effect of lincosamide? | GIT and acute colon inflammation |
Uses for clindamycin? | G+ cocci.
Penicillin resistant staph.
Topical use - Staph Conjunctivitis |
Sodium fusidate is an example of? | A fusidic acid |
What does fusidic acid treat that the other 50S inhibitors do not? | Osteomyelitis. Other than that it is used in similar circumstances to clindamycin |
What is the MOA of streptogramins? | They block tRNA attachment to 50S and cause premature peptide release |
What are two examples of streptogramins? | Quinupristin and Dalfopristin |
Are streptogramins first or last choice? | They are only used for serious infections:
MRSA, vancomycin-resistant enterococci, penicillin-resistant strep pneumoniae |
What is linezolid an example of? | An oxazolidinone |
What is it used to treat? | Serious cases:
C Diff.
G+s (e.g. MRSA).
Vancomycin-resistant enterococci.
Penicillin-resistant staph pneumoniae |