Test Two: Penicillin Alternatives

Question 0

1st gen cephalosporins

Answer 0

Cephalexin: Good for gram+ aerobes and MSSA. Less active for gram- and no enterococci activity. Good for soft tissue infxn and surgical prophy

Question 1

What is the mechanism of action of cephalosporins?

Answer 1

Inhibit cell wall peptidoglycan synthesis by blocking transpeptidase and carboxypeptidase

Question 2

2nd gen cephalosporins

Answer 2

Cefamandole: mainly gram- with less staph activity and some anaerobic effect

Question 3

3rd gen cephalosporins

Answer 3

Cefoperazone: Mostly Gm –ve, penicillin resistant streptococcus pneumoniae, with a subset effective against pseudomonas. Not used much in dentistry

Question 4

4th gen cephalosporins

Answer 4

Cefepime: Wider antibacterial spectrum (pseudomonas, penicillin resistant Streptococcus pneumoniae, MRSA, enterococcus, and hyper β-lactamase producing organism). Administered IV

Question 5

What cephalosporin penetrates the CSF for meningitis?

Answer 5

Cephotaxime

Question 6

How do 1st gen cephs respond to beta lactamase?

Answer 6

Very sensitive to hydrolysis

Question 7

Dosing for 1st gen ceph?

Answer 7

500mg qid. T1/2 is 1 hr

Question 8

2nd gen ceph kinetics

Answer 8

Lower peak plasma level than 1st. T1/2 1-1.5 hrs. 200-400 mg bid. Not widely used

Question 9

What are some adverse rxns for cephalosporins?

Answer 9

• Hypersensitivity (cross allergy with penicillin(~20%)
• Maculopapular rashes
• Transient increase in liver function.
• Inhibit hemostasis (hypoprothrombinemia)
• Alcohol intolerance

Question 10

Carbapenems (imipenem and miropenem)

Answer 10

Broad spectrum, beta lactamase resistant, used as alt for MRSA and strep pneumoniae, has cross allergenicity

Question 11

Monobactams (aztreonam)

Answer 11

Aerobic gram-, only injected, sensitive to beta lactamase, no cross allergenicity

Question 12

Examples of macrolides and mechanism of action

Answer 12

Erythromycin, clarithromycin, azithromycin, bind to 50s ribosomal subunit to block translation, hardly any allergies

Question 13

Erythromycin spectrum and dosage

Answer 13

Gram+ aerobes and facultatives, 250-500 mg q6h as enteric coated tablets bc of poor acid resistance, excreted in urine, does not reach brain or CSF

Question 14

Erythromycin adverse rxns

Answer 14

Epigastric pain, ventricular arrhythmia, hepatotoxicity (hepatic microsomal enzyme inhibitor-helps prolong action of other drugs)

Question 15

Clarithromycin diff from erythromycin

Answer 15

Similar spectrum but mainly gram+ anaerobes, rapid absorption, less GI problems, dosing is 250-500 bid, liver and kidney excretion

Question 16

Azithromycin

Answer 16

Rapid absorption, more active against strep/staph but mainly gram- anaerobes, stays in tissue for slow release (take 250 qd), excreted by liver

Question 17

When should macrolides be used?

Answer 17

1- Best alternative for B-lactam –allergic patient for acute orofacial infections
2- treat acquired bacterial pneumonia
3- chronic sinusitis
4- Asthma complications

Question 18

What are contraindications for macrolides?

Answer 18

Patient with cholestatic hepatitis and cardiac arrhythmia

Question 19

Clindamycin spectrum and mechanism of action

Answer 19

Gram+ and gram- anaerobes, binds to 50s subunit

Question 20

Clindamycin kinetics

Answer 20

• Completely absorbed after oral administration
• Widely distributed, penetrate well into bones
• Metabolized in the liver and its metabolites have also antimicrobial activity
• Excreted in urine and feces

Question 21

Clindamyin dosage and uses

Answer 21

150-300 q6h, Mainly used for bone infection, female genital
tract, pelvic and abdomenal infection.
- For acute orofacial infections for oral microbial resistance to the β-lactam antibiotics.

Question 22

Side effect of clindamycin

Answer 22

Some develop diarrhea and can get pseudomembranous colitis

Question 23

Vancomycin spectrum and mechanism of action

Answer 23

Effective against gram+ like MRSA, gram- bacilli are resistant, binds to terminal amino acids to block carboxypeptidase

Question 24

Vancomycin dosage and administration

Answer 24

Poorly absorbed oral, given iv, t1/2 is 6hr, 500 q6h

Question 25

Vancomycin side effects

Answer 25

Can have hypersensitivity like penicillin, can also cause nephrotoxicity esp in combo with other drugs

Question 26

Metronidazole uses

Answer 26

1-Protozoal infections (Giardiasis, Trichomoniasis, amebiasis)
2-Anerobia bacterial causing orofacial infection (periodontitis, acute necrotizing ulcerative gingivitis)

Question 27

Metronidazole kinetics

Answer 27

completely absorbed from GIT- oral intake attains peak level in 1-2 hours, widely distributed with excellent CNS penetration ( half
life= 8 hours)

Question 28

Side effect of metronidazole with alcohol

Answer 28

Disulfiram like action-blocks alcohol dehydrogenase which causes a buildup of acetaldehyde–> nausea, vomiting, flushing, tachycardia

Question 29

Fluoroquinolone mechanism of action

Answer 29

Inhibits bacterial gyrase and topoisomerase to prevent supercooling of DNA which stops replication

Question 30

Uses and dosage for fluoroquinolones

Answer 30

or UTIs, respiratory infections, GIT, bone, prophylaxis, 250-750 bid (very long 1/2 life, 10-12hrs, good for fewer dosages needed)

Question 31

Most commonly prescribed fluoroquinolones

Answer 31

Ciprofloxacin 250-500 bid, ofloxacin (topical), levofloxacin 250-500-750 qd (all 2nd generation bc there are generic forms)

Question 32

Side effects with fluoroquinolones

Answer 32

most imp is arrythmia–can disturb ECG, be careful when taking with anti arrhythmic drugs, theophylline or NSAIDs (CNS toxicity)