Anti Microbial Extra Qns Flashcards
How is penicillin V administered?
Oral (penicillin V has better absorption than pen G)
How does penicillinase resistant penicillin confer protection against beta lactamase catalysis?
Penicillinase resistant penicillin have bulky side groups that protect the beta lactam ring from beta lactamases
List 4 mechanisms of resistance to penicillin.
- Expression of efflux pumps -> pump antibiotics out
- Altered PBP -> reduce affinity for penicillins
- Production of beta lactamase -> destroys the beta lactam
- Bacteria decreases porin production -> prevents antibiotics from entering -> decreases intracellular drug concentration
What are the adverse reactions to penicillins?
- Allergy/hypersensitivity (SJS, TEN, Anaphylaxis)
- CDAD
How is piperacillin administered?
IV
How is augmentin (amoxicillin, clavulanic acid) administered?
Oral, IV
How is unasyn (ampicillin, sulbactam) administered?
IV
How is zosyn (piperacillin, tazobactam) administered?
IV
What is the coverage for Aztreonam?
Aztreonam covers gram negative bacteria only except ESBL
How is aztreonam administered?
IV
Does Aztreonam have cross-sensitivity with other penicillins?
No (only cephalosporins and carbapenams have cross sensitivity with penicillins)
How is vancomycin administered? What is the exception?
IV (only oral vancomycin is given for CDAD)
What is the action of mechanism of tetracycline/tigecycline?
Tetracycline binds to the 30S subunit. It prevents the binding of tRNA to the A site of the mRNA-ribosome complex, inhibiting protein synthesis.
Is tetracycline bacteriostatic or bactericidal?
Bacteriostatic (arrests cell growth)
Should tetracyclines be given with beta lactams?
No. Beta lactams are bactericidal that work in actively growing cells.
Are beta lactams bacteriostatic or bactericidal?
Bactericidal
How are the 3 tetracyclines administered?
Tetracycline (oral)
Doxycycline (oral, IV)
Minocycline (oral)
What is the action of mechanism for aminoglycosides?
They bind to 30S ribosome subunit, distorts structure of ribosome, causing misreading of mRNA
Are aminoglycosides bacteriostatic or bactericidal?
Bactericidal
What is the action of mechanism for macrolides?
Macrolides bind to 50S ribosomal subunit, inhibiting the translocation step, thus inhibiting protein synthesis
CSF penetration for macrolides?
Macrolides have poor CSF penetration
MACROLIDES HAVE Drug Drug Interactions
MACROLIDES HAVE Drug Drug Interactions
List the 2 mechanisms of resistance to macrolides.
- ERM gene expression -> ribosomal methylation -> reduced binding of macrolides to 50S ribosomal subunit
- Efflux pumps
CSF penetration for clindamycin?
Clindamycin have poor CSF penetration
What drug does clindamycin have cross-resistance with?
Erythromycin (ERM gene expression)
If erythromycin resistance is due to ERM gene, will clindamycin be effective?
If erythromycin resistance is due to ERM gene, clindamycin will NOT be effective
If erythromycin resistance is due to increased expression of efflux pumps, will clindamycin be effective?
If erythromycin resistance is due to increased expression of efflux pumps, clindamycin is EFFECTIVE as it is not a substrate for the efflux pumps
What does Azithromycin treat?
Atypical microbes
FLUOROQUINOLONES have Drug Drug Interactions
FLUOROQUINOLONES have Drug Drug Interactions
What are the 2 classes of drugs in nucleic acid synthesis inhibitors?
Fluroquinolones (Ciprofloxacin, Levofloxacin, Moxifloxacin)
Anti-folate drugs (Sulfonamides, Trimethoprim, Co-trimoxazole)
How are fluoroquinolones administered?
IV / Oral (good oral availability, taken 2h before or 6h after dairy food)
How are anti folate drugs administered?
ORAL
Where are sulfa drugs acetylated and conjugated?
sulfa drugs are acetylated and conjugated in the liver which leads to crystaluria
List the adverse effects of sulfonamides.
- Crystaluria -> Nephrotoxicity
- Hematological disturbances
- Kernicterus (avoid in newborns and infants)
Contrindications of Nitrofurantoin
- Pregnant women in their last trimester
- Patients with G6PD deficiency
- Patients with upper tract UTIs
What is nitrofurantoin active against?
E. coli and Enterococcus
CSF penetration for 5-Flucytosine?
Good CSF penetration
CSF penetration for Echinocandins?
Poor CSF penetration
What are the 4 triazoles?
Fluconazole, Posaconazole, Itraconazole, Voriconazole
CSF penetration of fluconazole
good CSF penetration
CSF penetration of itraconazole
poor CSF penetration
CSF penetration of voriconazole
good CSF penetration
List the adverse effects of imidazoles
- Contact dermatitis
- Vulvar irritation
- Oedema
What drug treats tinea infections?
Miconazole, Oral Terbinafine treats tinea capitis
What is an anti-protozoal agent?
Metronidazole
How is metronidazole administered?
Oral
What is the mechanism of action for Metronidazole?
Nitro group of metronidazole serves as an electron acceptor forming cytotoxic free radicals, leading to protein and DNA damage
What amebicide is metronidazole?
Mixed amebicide (acts on both parasite in the lumen and act on amoebas in intestinal wall)
What metabolism does metronidazole undergo?
Hepatic metabolism (moxifloxacin also)
Adverse effects of metronidazole.
- Unpleasant metallic taste
- GI effects (nausea, vomiting)
Can metronidazole be used in pregnancy?
Yes but avoid use in first trimester
What drugs have poor CSF penetration?
Itraconazole, Echinocandins, Macrolides, Aminoglycosides
What drugs have drug-drug interactions?
Fluoroquinolones, Macrolides, Triazoles, Rifampicin (given with vitamin K)
Can beta-lactams be used in pregnancy?
Yes
What drug is useful for empirical treatments?
Aminoglycosides
What does co-trimoxazole do?
It interferes with tetrahydrofolate synthesis
Which 2 NRTIs are safe to use in pregnancy?
Emtricitabine and Tenofovir
How are all NRTIs administered?
Oral
What does Ganciclovir treat?
All herpesvirus, especially active against cytomegalovirus
What does Acyclovir treat?
Herpes simplex virus types 1 and 2, varicella-zoster virus (acyclovir is more active against HSV than VZV)
What is the advantage of using pro-drugs valacyclovir and valganciclovir for treatment?
It has much better oral bioavailability and administered with lesser dosing frequency (but its COSTLY)
Adverse effect of NNRTI
CNS effects
What is integrase inhibitor active against?
HIV-1 and HIV-2
What is NNRTI?
It is a non-competitive inhibitor of HIV-1 RT. (NOT used against HIV-2)