Antibiotics Flashcards
Families of Beta Lactams
- Penicillins
- Cephalosporins
- Carbapenems
Classes of Antibiotics
- Beta Lactams
- Glycopeptides
- Fluoroquinolones
- Aminoglycosides
- Lincosamides
- Tetracyclines
- Macrolides
- Oxazolidinones
- Sulfonamides
- Metronidazole
Beta-lactams MOA
bind to penicillin binding proteins, interfere with cell wall synthesis
What is beta lactamase?
an enzyme produced by all Gram negative bacteria which hydrolyzes B-lactam ring of penicillins and cephalosporins and destroys their antibiotic activity
How do beta lactamase inhibitors work?
they bind beta lactamase and improve spectrum of antibiotic
Examples of beta lactamase inhibitors
- clavulanic acid (added to amoxicillin)
2. tazobactam (added to piperacillin)
Categories of Penicillins
- Narrow-spectrum
- Aminopenicillins - greater gram negative coverage
- Broad spectrum - often with beta lactamase inhibitor
Mechanisms of Resistance to Penicillins
- Presence of lipopolysaccharide outer layer
- variations in penicillin binding protein –> decreased binding of beta lactam
- Production of beta lactamase
Clearance of penicillins
80% cleared by kidneys w/in 4 hours
Contraindications of penicillins
Renal dysfunction - must adjust dose
Examples of penicillins
- Penicillin G (IV)
- Penicillin V (PO) aka Penicillin VK
- Amoxicillin (Amoxil, Trimox) - aminopenicillin
If you give a pt amoxicillin and they develop a flat, itchy rash, what should you consider?
Mono
Side Effects of Penicillins
- Hypersensitivity (mild rash to anaphylaxis)
- Nausea/Vomiting
- Diarrhea
- Stinging w/ IV
If pt has allergic reaction to penicillin, how would you handle other beta-lactams?
OK with mild reactions, but do not prescribe if they had severe hypersensitivity OR had mild reaction but also has pulmonary issues
What kinds of bacteria would you prescribe penicillins for?
- Very good for Gram +
- Animopenicillins and broad spectrum good for Gram -
- Broad spectrum very good for anaerobes
- Broad spectrum good for pseudomonas
- IV Penicillin G good for Neisseria meningitidis
What can you use to treat Neisseria meningitidis?
IV Penicillin G
How many generations of Cephalosporins are there? What is the significance of the generations?
4
As you move up generations, coverage expands.
Example of 1st generation cephalosporin
Cephalexin/Keflex
Example of 2nd generation cephalosporin
Cefaclor/ceclor
Example of 3rd generation cephalosporins
Ceftriaxone/Rocephin
Cefdinir/Omnicef
What is a good antibiotic for meningitis or encephalitis and why?
3rd gen cephalosporins b/c they have good CNS penetration
Excretion of Cephalosporins
- Renal excretion so adjust dose
2. Except ceftriaxone which has liver excretion so adjust dose
What kinds of bacteria can you treat with cephalosporins?
- Very good (esp 1) for Gram +
- Gens 2&3 very good for Gram -
- Gens 2&3 good for anaerobes
- Ceftazidime and 4th gen very good for pseudomonas
Contraindications of Cephalosporins
- Anaphylaxis to penicillins!!!!
2. Nonanaphylactic allergy is relative contraindication, cross reactivity is 2-10%
Side Effects of Cephalosporins
- Low WBC
- Nephrotoxicity
- C. diff (pseudomembranous colitis)
What is a good antibiotic choice for skin infections?
1st gen cephalosporins
What is a good prophylactic antibiotic prior to surgery?
1st gen cephalosporins
What would you prescribe for an intra-abdominal infection?
2nd gen cephalosporin
2nd gen cephalosporins good for
- intra-abdominal infections
2. OK for mild infections predicted to be due to Gram - bacteria
What are 1st gen cephalosporins good for?
- Skin infections
2. Prophylaxis prior to surgery
What are 3rd generation cephalosporins good for?
severe infections in combination with another drug of a different class
What are 4th gen cephalosporins good for?
severe hospital facility acquired infections
What is unique about carbapenems?
only IV, “big gun” for severe infections
Excretion of Carbapenems
kidney - adjust dose
What kinds of bacteria are carbapenems good for?
very good for Gram + and - bacteria, anaerobes, pseudomonas, SPACEs, ESBL (very good coverage)
Indication for carbapenems
Severe infections, suspected resistant organisms
Contraindications for carbapenems
imipenem causes seizures
Side effects of carbapenems
Nausea/vomiting, neurotoxicity (seizure, lightheadedness, dizziness), fever
Examples of glycopeptides
vancomycin/vancocin
Glycopeptide MOA, bactericidal or static?
inhibit cell wall synthesis, bactericidal
Mechanism of Resistance against Glycopeptides
- variation in amino acid precursor so that drug cannot bind
- excess cell was production
- biofilm production
What is the half life of vancomycin?
6 hours
How are glycopeptides administered?
- PO if infection in GI tract (C. diff)
2. IV or IM if infection outside GI tract
Clearance of Glycopeptides
kidney –> adjust dose
What kinds of bacteria are glycopeptides used for?
- very good for Gram +
- very good for MRSA
- Good for C. diff and enterococcus
Contraindications for glycopeptides
any ototoxic medications
Side effects of glycopeptides
- IV causes histamine release –> drop in BP and flushing
- Ototoxicity if administered with another ototoxic agent (ie. loop . diuretic)
- Nephrotoxicity if administered with another nepthrotoxic agent
- Neutropenia in immunocompromised pt
If you want to prescribe a glycopeptide, what do you need to check the patient’s med list for?
ototoxic medication ie. loop diuretic, aminoglycoside
Examples of Fluoroquinolones
- Ciprofloxavin/Cipro
- Levofloxacin/Levaquin
- Moxifloxacin/Avelox
Fluoroquinolones MOA, bactericidal or static?
inhibits DNA replication and transcription, bactericidal
Mechanisms of Resistance - Fluoroquinolones
- Mutations in topoisomerase (target)
2. Altered pumps that actively pump drug out of cell
Absorption of Fluoroquinolones
absorbed very well from gut, easy transition from IV to PO
Clearance of fluoroquinolones
- Most via kidney –> adjust dose
2. Moxifloxacin via liver –> adjust dose
What kinds of bacteria are fluoroquinolones effective against?
- good for Gram +
- very good for Gram -
- Levofloxacin and moxifloxacin are good for anaerobes
- good for chlamydia
- good for mycobacterium avium
What speciality are fluoroquinolones most used in?
Urology
Fluoroquinolones are a good back up for _____
macrolides
Contraindications for fluoroquinolones
- Pregnancy!!!!
- Children!!!
- NSAIDs so need to stop these temporarily (otherwise dizziness, lightheadedness, seizures)
Side Effects of Fluoroquinolones
- Generally well tolerated
- Nausea/Vomiting
- Diarrhea
- Tendon ruptures (rare)
Examples of Aminoglycosides
Gentramicin
Where do you seen aminoglycosides used the most?
inpatient IV (because requires high surveillance of kidney function)
Aminoglycosides MOA
inhibit protein synthesis
Mechanisms of Resistance - Aminoglycosides
- ribosome alteration
- decreased permeability
- inactivation by aminoglycoside modifying enzymes
Absorption of Aminoglycosides
- poorly absorbed in GI tract
2. usually IV
Spectra of Aminoglycosides
- very good for Gram -
2. good for pseudomonas
Contraindications for Aminoglycosides
Renal Dysfunction!! (May adjust dose if stage 1 but o/w don’t do it)
What must you monitor when giving aminoglycosides?
Kidney function PRIOR to and THROUGHOUT therapy
Side Effects of aminoglycosides
- Ototoxicity
2. Nephrotoxicity
Examples of Lincosamides
Clindamycin
What are lincosamides most commonly used for?
- dental infections
- bone infections
- used after macrolides if have beta-lactam allergy
Lincosamides MOA, bactericidal or static?
Inhibits protein synthesis, generally bacteriostatic
Mechanisms of Resistance - lincosamides
- mutation of ribosomal receptor site
2. enzymatic inactivation
If a bacteria has resistance to clindamycin, what does this usually imply?
cross-resistance to macrolides
Clearance of lincosamides
Liver –> dose adjustments
Absorption of lincosamides
well absorbed orally
Spectra of Lincosamides
- good for Gram +
- very good for anaerobes
- good for severe Gram + infection in combo w/ other bactericidal drugs
Contraindications for Lincosamides
None
but remember liver metabolism
Side effects of lincosamides
high incidence of C. diff
Examples of Tetracyclines
- Tetracycline
- Doxycycline (oracea, doryx)
- Minocycline (minocin)
What are tetracyclines commonly used for?
acne, Q-fever, lyme disease
What do you prescribe for Lyme disease?
doxycycline
Frequency of dosage for the 3 tetracyclines
- Doxy and mino are BID
2. Tetra is 4x/day
Tetracyclines MOA, bactericidal or static?
inhibits translation, bacteriostatic
Mechanisms of Resistance - tetracyclines
- pumped out
- ribosomal protection
- enxymatic inactivation
What shoud you not take with tetracyclines?
- Calcium
- Magnesium
- Food
Clearance of tetracyclines
kidney –> dose adjustments
Spectra of Tetracyclines
- Good for Gram +/-
2. good for intracellular organisms (chlamydia, mycoplasma, rickettsia), spirochetes (syphilis, borreliosis), malaria
What antibiotic is good for tick-born infection and especially considered for patients who work with cattle, sheep, goats?
Tetracyclines
Contraindications for tetracyclines
- Pregnancy and Lactation
2. Children <8 yo (b/c tooth discoloration)
Side effects of tetracyclines
- Nausea, vomiting, diarrhea
- Mottling of teeth
- photosensitivity
- diabetes insipidus
- liver damage
- kidney damage
- headache –> pseudo tumor cerebri (increased intracranial pressure)
What do you prescribe for acne?
Doxycycline
If you have a patient being treated for acne and they develop an insidious, low-grade, daily headache, what should you consider?
That it may be due to the tetracycline. Refer to ophthalmology to look for papilledema.
Examples of Macrolides
- Erythromycin (ery-tab)
- Azithromycin (Zithromax, z-pak)
- Clarithromycin (Biaxin)
What can you use to treat gastroparesis?
erythromycin
When is a good time to use macrolides?
when patient cannot take beta-lactam
Macrolides MOA, bactericidal or static?
inhibits protein synthesis (translation), generally bacteriostatic
What other effect dose erythromycin have?
stimulates motilin receptors on GI smooth muscles, increases transit of GI contents, can cause diarrhea
Mechanism of resistance - Macrolides
- pumped out
- esterase hydrolyzes macrolides
- complete cross resistance (if resistant to one, resistant to whole class)
Half life and dosing for azithromycin
“long half life”
double dose the first day (250mg BID), then 250mg QD for 2-5 days
Metabolism of macrolides
liver
Drug interactions with macrolides
liver metabolized drugs ie. STATINS (must hold)
Common side effect of clarithromycin
metallic taste in mouth
Spectra of Macrolides
- Very good for Gram +/-
2. good for atypical bacteria (rickettsia, chlamydia, legionella, gonorrhea)
What do you commonly prescribe for STI’s?
clarithromycin or azithromycin
What is commonly used to treat pneumonia?
macrolides
Examples of Sulfonamides
- Sulfamethoxazole
2. Silver sulfadiazine/sulfacetamide (topical)
Example of folate synthesis inhibitor (non-sulfas)
Trimethoprim
What is the name of the combination sulfa/folate synthesis inhibitor antibiotic?
Bactrim (Septra) - combination of sulfamethazole and trimethoprim
What is commonly used to treat UTIs?
Bactrim
What is commonly used for prevention of infection in HIV patients?
Bactrim
Sulfonamides MOA
inhibit folate synthesis
Trimethoprim MOA
inhibit folate synthesis at different step than sulfas
Mechanism of resistance to sulfonamides
- overproduction of PABA
- Enzyme mutation that leads to reduced affinity for binding sulfas
- pumped out
How are sulfas administered?
- PO, always w/ trimethoprim
2. topical for burns
Metabolism of sulfonamides
Metabolized by liver and excreted by kidney –> dose adjustments for patients with advance renal dysfunction
Spectra of Sulfa and other
- good for Gram +/-
2. good for PJP (pneumocystic jiroveci) which is an opportunistic infection seen in HIV patients
Side effects of sulfonamides
- Steven-Johnson syndrome
- Hemolytic anemia, aplastic anemia, granulocytopenia, thrombocytopenia
- kernicterus (high bilirubin)
Contraindications for sulfonamides
- allergy to sulfa antibiotics
2. G6PD deficiency
What is Steven-Johnson syndrome?
A rare but life-threatening hypersensitivity that causes skin to start peeling/sloughing off.
If a patient had any reported skin or mucous membrane reactions, what would you be cautious prescribing and why?
Sulfonamides because they can cause Steven-Johnson syndrome
Common uses for sulfonamides
UTIs, URIs, PJP prophylaxis
Topical sulfa to prevent infection secondary to burn
What is commonly used to treat respiratory infections?
Bactrim
Examples of Metronidazole
Metronidazole/Flagyl
Is metronidazole bactericidal or static?
Cidal
What does metronidazole work against?
protozoa (trichomonas, giardia, entamoeba), anaerobic bacteria, C. diff
Route of administration of metronidazole
PO, good absorption
Metabolism of Metronidazole
Liver –> dose adjustment
What is metronidazole used to treat?
bacterial vaginosis
giardia
C. diff if cannot take vancomycin
What is first line treatment for C. diff?
vancomycin
Side effects of metronidazole
Nausea, metallic taste, rarely CNS toxicity, neutropenia, pancreatitis, peripheral neuropathy, hepatitis
Contraindications for Metronidazole
- Cannot be taken with alcohol!! (will have severe nausea/vomiting)
- Pregnancy
What is the Disulfiram reaction?
Build up of acetaldehyde causing severe nausea, vomiting. Seen in antabuse which is used for recovering alcoholics
When do you have to worry about the disulfiram reaction?
When patients mix Metronidazole with alcohol