macrolides, clindamycin and linezolid

Question 1

what type of macrolides are there

Answer 1

erythromycin, azithromycin, clarithromycin

Question 2

are macrolides bacteriostatic or bactericidal

Answer 2

bacteriostatic

Question 3

What is the mechanism of action for macrolides

Answer 3

inhibit proten synthesis by reversibly binding to 50S ribosomal subunit

inhibit translocation step, nascent peptide chain residing at the A site of the transferase reaction fails to move to the peptidyl donor site

Question 4

what is the problem with macrolide in terms of metabolism

Answer 4

it inhibits cp450 enzymes, therefore results in many drug drug interactions

Question 5

What is erythromycin used to treat

Answer 5

treat community acquired pneumonia, s. pneumoniae, atypical bacteria

Question 6

what is clarithromycin used to treat

Answer 6

higher activity against atypical bacteria than erythromycin

eg. legionella, helicobacter pylori

Question 7

what is azithromycin use to treat

Answer 7

more active than erythromycin against respiratory infections due to H. influenzae and moraxella catarrhalis

Question 8

What is azithromycin prefered for

Answer 8

STD caused by chlamydia trachomatis and neisseria gonorrhoea

Question 9

What are the adverse effects of macrolides

Answer 9

GI distress and mobility

hepatotoxicity

ototoxicity

May prolong QT interval, used in caution with patients with pro arrhythmic condition

Question 10

Who is contraindicated for macrolide

Answer 10

patients with hepatic dysfunction

clarithromycin cat C

Question 11

How does erythromycin and clarithromycin affect accumulation of other compounds

Answer 11

they inhibit c450 enzymes, potentiating effects of these drugs like corticosteroids, digoxin and warfarin through the interference of CYP mediated metabolism of these enzymes

Question 12

What is clindamycin very useful for

Answer 12

very useful against anaerobic infection

Question 13

what is the mechanism of action for clindamycin

Answer 13

binds exclusively to 50s subunit of bacterial ribosomes and inhibit peptide synthesis

Question 14

what is clindamycin not used with

Answer 14

macrolides, as they can act at sites of proximity, can antagonise each other

Question 15

what can clindamycin have a high risk of causing

Answer 15

CDAD

Question 16

what are the indications for clindamycin

Answer 16

MRSA, streptococcus, penicillin resistant anaerobic bacteria

anaerobic infection of skin and soft tisssue caused by bacteroides, clostridiodes perfringens

Good spectrum of activity against oral pathogens. 50% of oral pathogens caused by anaerobes, excellent alternative to penicillin for treatment of dental abscesses because of bacterial susceptibility to drug

prophylaxis against endocarditis prior to dental procedures in patients with acquired valvular damage, congenital heart disease, valve replacement, cardiomyopathy

Question 17

What is resistant to clindamycin

Answer 17

almost all aerobic gram negative bacteria

Question 18

what is the administration for clindamycin

Answer 18

IV and Oral, can be topical solution, gel or lotion

Question 19

How is the distribution of clindamycin

Answer 19

excellent bone and salivary gland production

poor entry into CSF

Question 20

How is clindamycin metabolised

Answer 20

hepatic

Question 21

What are the adverse effects of clindamycin

Answer 21

skin rashes,
CDAD diarrhoea, take full glass of water to reduce esophageal irritation

Question 22

what does linezolid covers

Answer 22

only gram positive

Question 23

what is the mechanism of linezolid

Answer 23

binds to 23 S ribosomal RNA of 50s subunit, prevent formation of functional 70S inititation complex, an essential component of bacterial translation

prevents formation of initiation complex

Question 24

What is linezolid good for

Answer 24

Staph, strep, enterococci, listeria monocytogenes

Good for penicillin resistant strain of S.pneummoniae, MRSA, VRSA, VRE

Question 25

why is linezolid not good for gram negative bacteria

Answer 25

because efflux pump force linezolid out of cell faster than it can accumulate

Question 26

How can linezolid be administered

Answer 26

orally and IV

Question 27

How is the distribution of linezolid

Answer 27

widely distributed, good penetration into CSF

Question 28

what are some adverse effects of linezolid

Answer 28

GI effect: nausea, diarrhea, headache rash

Bone marrow supression: leading to thrombocytopenia

Can have non selective monoamine oxidase inhibitor activity leading to serotonin syndrom

Irreversible peripheral neuropathies and optic neuritis associated with more than 28 days of use