Module 3 Flashcards
Antimicrobials
Beta-lactam antibiotics MOA
Interfere with cell wall synthesis by binding to penicillin-binding proteins (PBP), transpeptidase enzymes that catalyze peptidoglycan cross-linking. This compromises the overall cell wall integrity leading to osmotic lysis making beta-lactams bactericidal.
Penicillin structure
consists of a thiazolidine ring, a side chain, and a beta-lactam ring which is essential for antibiotic activity
Natural penicillins
penicillin G and penicillin V
Semisynthetic penicillins (aminopenicillins/extended-spectrum penicillins)
ampicillin and amoxicillin
Antistaphylococcal penicillins
developed to resist hydrolysis by staphylococcal beta-lactamases and include methicillin, nafcillin, oxacillin, and dicloxacillin
Ureidopenicillin/Antipseudomonal penicillin
piperacillin
beta-lactamase inhibitors
enhance the ability of beta-lactams to fight bacteria by inhibiting an enzyme produced by the bacteria which deactivates beta-lactams like penicillin, include sulbactam, clavulanate, and tazobactam (do not work against all beta-lactamases)
beta-lactam and beta-lactamase inhibitor combos available
ampicillin/sulbactam (Unasyn - IV), amoxicillin/clavulonate (Augmentin - PO), and piperacillin/tazobactam (Zosyn - IV)
penicillin G,V antibacterial spectrum
gram-positive streptococcus pneumoniae, group A strep, group B strep, group C,G strep, and Viridans streptococci (seen with IVDU) and gram-negative cocci including Neisseria meningitidis. Anaerobes including peptostreptococcus, prevatella spp., fusobacterium spp., clostridium spp., spirochetes including treponema pallidum and borrelia burgdorferi, and other organisms including Pasteurella multocida (cat bites). No staph coverage.
Penicillin administration
penicillin G has poor oral bioavailability, requires frequent IV dosing due to short half-life (0.5 hours), and requires dose and interval adjustment for renal insufficiency. Penicillin G IM formulations are available (procaine and benzathine penicillin). Penicillin V has better oral bioavailability.
Antistaphylococcal penicillins antibacterial spectrum
active against gram-positive cocci covered by pen G as well as S. aureus and S. epidermidis, no gram-negative coverage
Antistaphylococcal penicillin administration
short half-lives, nafcillin and oxacillin require frequent IV/IM dosing whereas dicloxacillin is administered PO, no dose adjustment is required for renal and hepatic impairment for dicloxacillin and oxacillin but caution should be taken with nafcillin in patients with concomitant renal and hepatic impairment
Semisynthetic penicillins (ampicillin and amoxicillin) antibacterial spectrum
similar gram-positive activity to pen G but slightly less active against group A strep, group B strep, and S. pneumoniae. Ampicillin is more active against Listeria monocytogenes (cause of meningitis in immunocompromised patients, newborns, and elderly) and 2X more active against enterococci than penicillin. Has some activity against gram-negative H. influenzae and E. coli (40% ampicillin resistance due to beta-lactamases). Not useful for S. aureus infections.
Ampicillin administration
requires frequent IV dosing (q 4-6 hours) due to short half-life and dose adjustment with renal insufficiency, has fair oral bioavailability
Amoxicillin administration
has better oral availability than ampicillin but can be administered by IV (1-2 g q 6 hours), most active of the penicillins against penicillin-resistant S. pneumoniae
How does combining beta-lactamase inhibitors with ampicillin and amoxicillin increase their spectrum of activity? (Unasyn and Augmentin)
Increases activity against gram-positive methicillin-sensitive S. aureus (MSSA), gram-negative H. influenzae producing beta-lactamase, E. coli, K. pneumoniae, and K. oxytoca, and Anaerobic Bacteroides fragilis.
Piperacillin-Tazobactam (Zosyn) antibacterial spectrum
has similar gram-positive activity to ampicillin and excellent streptococcal coverage as well as expanded gram-negative activity against Pseudomonas aeruginosa (associated with diabetic would infections), Serratia marcescens, and Enterobacter spp. Excellent anaerobic activity against B. fragilis. Useful for nosocomial pneumonia, intra-abdominal infections, and complicated wound infections. No MRSA coverage.
Piperacillin-Tazobactam (Zosyn) administration
Requires frequent IV dosing (no oral) due to short half-life (1 hour) and is usually 4.5 g IV q 6 hours for Pseudomonas but q 8 hours for non-Pseudomonas. Requires dose and interval adjustment for renal insufficiency.
narrow-spectrum, beta-lactamase susceptible drugs (natural penicillins) general antibacterial activity
active against strep, enterococci, anaerobes (except B. fragilis), and spirochetes (most staph aureus resistant)
Why is methicillin not used clinically anymore in the United States?
it has the potential to cause acute interstitial nephritis
very narrow-spectrum, beta-lactamase resistant drugs (Antistaphylococcal penicillins) general antibacterial activity
active against S. aureus (MSSA), S. epidermidis, and strep
wider spectrum, beta-lactamase susceptible drugs (semisynthetic penicillins) general antibacterial activity
active against strep, enterococci, Listeria monocytogenes, beta-lactamase negative E. coli, Haemophilus influenzae, and Moraxella catarrhalis (staph aureus is resistant)
broad-spectrum, anti-gram-negative, beta-lactamase susceptible drugs (antipseudomonal) antibacterial activity
retains the activity of ampicillin and is also active against Pseudomonas aeruginosa (staph aureus is resistant)
What is the main structural difference between penicillins and cephalosporins?
Cephalosporins contain R1 and R2 side chain substitutions which alter their antibacterial spectrum and pharmacokinetics making them resistant to hydrolysis by many penicillinases (beta-lactamases)
What are the main similarities between penicillins and cephalosporins?
Both penicillins and cephalosporins contain beta-lactam rings which inhibit cell wall synthesis and are bactericidal
How does the antimicrobial activity of cephalosporins change as the generation increases?
Lower-generation cephalosporins have more activity against gram-positive organisms (staph and strep) and higher-generation cephalosporins have more activity against gram-negative and less activity against gram-positive organisms (more broad spectrum)
1st generation cephalosporins
cefazolin and cephalexin
2nd generation cephalosporin
cefoxitin, cefuroxime, cefotean, cefaclor, and cefprozil
3rd generation cephalosporins
ceftriaxone and ceftazidime
4th generation cephalosporin
cefepime
5th generation cephalosporin
ceftaroline
1st generation cephalosporins antibacterial spectrum
active against strep, S. aureus (MSSA), Proteus mirabilis, sensitive E. coli, and Klebsiella spp. (PEcK)
2nd generation cefuroxime antibacterial spectrum
improved gram-negative activity including beta-lactamase-positive H. influenzae and Neisseria spp. (HEN PEcKS) and slightly reduced gram-positive activity (crosses blood-brain barrier)
3rd generation ceftriaxone antibacterial spectrum
has the longest half-life of all the cephalosporins and retains the gram-positive activity of 1st generation cephalosporins but has improved gram-negative activity (used to treat community-acquired pneumonia and is the drug of choice for CNS infections - crosses blood-brain barrier), is also active against Neisseria gonorrhoeae.
3rd generation ceftazidime antibacterial spectrum
loses gram-positive activity but is active against gram-negative rods including Pseudomonas (used to treat nosocomial infections)
4th generation cefepime antibacterial spectrum
has excellent gram-negative and gram-positive activity against Pseudomonas (nosocomial infections)
5th generation ceftaroline antibacterial spectrum
effective against MRSA but has no Pseudomonas coverage (approved for CAP and acute bacterial skin infections) - only used for MRSA if there is an allergy to vancomycin (under lock and key)
Aztreonam (IV/IM) MOA
a monobactam beta-lactam antibiotic that binds to PBP3 preventing peptidoglycan cross-linking (has no cross-allergenicity with beta-lactams and used when allergy to penicillin)
Aztreonam antibacterial spectrum
has broad gram-negative activity including Pseudomonas aeruginosa but no gram-positive or anaerobic activity (used as an alternative to aminoglycosides and 3rd generation cephalosporins)
Vancomycin MOA
bactericidal non-beta-lactam antibiotic that inhibits cell wall synthesis by binding the D-Ala-D-Ala terminal of the forming peptidoglycan preventing cross-linking
Vancomycin antibacterial spectrum
narrow-spectrum activity against drug-resistant gram-positive infections (drug of choice for MRSA) and C. difficile (given PO because bacteria is in the colon), no gram-negative activity. VRE and VRSA resistant due to substitution of D-Lactate for terminal D-Alanine
Vancomycin administration
administered through IV unless for treating C. diff (oral) and dose adjustment required in renal impairment
Vancomycin adverse effects
infusion-related flushing (or red man syndrome) and dose-dependent ototoxicity and nephrotoxicity especially in the setting of other toxic drugs
Daptomycin MOA
bactericidal lipopeptide that disrupts the bacterial cell membrane
Daptomycin antibacterial spectrum
narrow-spectrum activity against gram-positive bacteria only (useful for treating infections due to resistant gram-positive cocci including MRSA and vancomycin-resistant enterococci - VRE)
Daptomycin administration
administered through IV only and dose interval adjustment required for renal impairment
Daptomycin toxicity
myositis (myopathy, muscle pain)
Carbapenems
synthetic beta-lactam antibiotics which only differ slightly in structure from the penicillins that are highly resistant to beta-lactamases (Imipenem, Meropenem, and Ertapenem)
Carbapenems antibacterial spectrum
broad-spectrum antibacterial activity against gram-positive cocci (MSSA, MSSE, and S. Pneumoniae, not MRSA or E. faecium), gram-negative rods and resistant gram-negative rods (Pseudomonas aeruginosa and Enterobacter spp.), and anaerobes
Carbapenem administration
administered through IV and penetrate well into body tissues and fluids including CSF when meninges are inflamed.
Imipenem administration
inactivated by renal dehydropeptidase (DHP) so is administered with cilastatin which inhibits DHPs
Adverse effects of Imipenem
Can cause encephalopathy and seizures, other carbapenems less likely to do so
extended spectrum beta-lactamases (ESBLs)
found mainly in E.coli and Klebsiella spp. but also occasionally found in different species of the Enterobacteriaceae, Pseudomonas, H. influenzae, and Neisseria gonorrheae (increasing use of 3rd generation cephalosporins has contributed to their rise)
Fosfomycin MOA
bactericidal through the inhibition of first step of bacterial cell wall synthesis and the enzyme pyruvyl transferase (given when patient has multiple allergies)
Fosfomycin antibacterial spectrum
activity against some MDR organisms including ESBL-producing E. coli but mainly used in treatment of UTIs particularly those caused by E. coli and Enterococcus faecalis
Fosfomycin administration
oral as a one-time 3 g dose, requires no dose adjustment for renal impairment
Fosfomycin most common adverse effects
diarrhea and vaginitis
Aminoglycoside MOA
Bactericidal protein synthesis inhibitor that targets the 30S subunit of bacterial ribosomes
Aminoglycoside antibacterial spectrum
synergistic with cell wall inhibitors (beta-lactams and vancomycin) with broad spectrum activity against many gram-negative rods including Pseudomonas. Most frequently used clinically for empiric therapy of serious infections caused by aerobic gram-negative bacilli, not effective against anaerobes.
Aminoglycoside administration
administered daily through IV/IM (except for Neomycin [oral] which is too toxic for IV) with limited tissue penetration and no CNS penetration, dose adjustment required for renal impairment
Aminoglycoside adverse effects
can have toxic effects on the kidney and both the auditory and vestibular components of the 8th cranial nerve (ototoxicity). Toxicity causes irreversible damage to the cochlear and vestibular cells depending on the length of exposure and loop diuretics. Longer courses of therapy can also cause reversible nephrotoxicity potentiated by other renal-toxic agents.
Aminoglycosides contraindication
patients with Myasthenia gravis due to risk of paralysis
Streptomycin clinical use
Second-line treatment for Tuberculosis but more toxic than newer agents
Gentamycin clinical use
used similar to Tobramycin for serious gram-negative infections including treatment of Pseudomonas (especially in CF), Enterobacter, Proteus, and undefined sepsis and endocarditis
Amikacin clinical uses
resistant to bacterial enzymes that inactive aminoglycosides like gentamycin and used only as last resort (under lock and key)
Neomycin clinical use
used as topical ointments or orally in surgical prophylaxis for bowel surgery
Tetracycline MOA
Bacteriostatic protein synthesis inhibitor that targets the 30S subunit of bacterial ribosomes
Tetracycline antibacterial spectrum
active against many gram-positive, and gram-negative bacteria, and atypicals, alternate choice for MRSA and VRE treatment
Tetracycline clinical use
tetracycline and doxycycline are most widely used to treat Chlamydia, Rickettsia, Mycoplasma (esp. M. pneumonia) infection, Tick-borne diseases, Gonococcal infections, pelvic inflammatory disease, anthrax, malaria, and tularemia. Can be used at lower doses to treat acne and rosacea.
Tetracycline administration
administered orally with food to minimize GI distress (absorption decreased by dairy food and antacids) and distributed to most body fluids including CSF but not at a high enough level to treat CNS infection. Doxycycline is the only tetracycline that can be given to patients with renal impairment
Tetracycline adverse effects
causes gastric discomfort if taken without food, photosensitivity, inhibition of bone growth in kids, discoloration of teeth of fetus and children brown, superinfections (yeast infections and C. diff), and vestibular side effects (dizziness, nausea, and vomiting)
Tetracycline contraindications
pregnancy and children under 8 years old
Tigecycline MOA
Bacteriostatic protein synthesis inhibitor that targets the 30S subunit of bacterial ribosomes, binding better than tetracycline and doxycycline. It is derived from minocycline and was specifically designed to overcome resistance to tetracycline/doxycycline which is mediated by efflux pumps and ribosomal protection.
Tigecycline clinical use
used to treat complicated infections by MRSA and VRE, complicated intra-abdominal infections, CAP, Enterobacteria, Mycobacteria, and all other tetracycline targets (under lock and key)
Tigecycline adverse effects
same as tetracyclines - N/V/D, photosensitivity, and chelation
Chloramphenicol MOA
Bacteriostatic protein synthesis inhibitor which binds to the 50S subunit of bacterial ribosomes and blocks aminoacyl from binding to the acceptor site, inhibiting peptidyl transferase reaction and translation.
Chloramphenicol antibacterial spectrum
widely distributed in tissues and crosses blood-brain barrier where it is active against many gram-positive and gram-negative bacterial including anaerobes, bactericidal against H. influenzae, S. pneumoniae, and N. meningitidis, VRE, and Rocky Mountain Spotted Fever
Chloramphenicol clinical use
use in the United States is limited by severe adverse reactions but it is used widely outside the country for treatment of bacterial meningitis
Chloramphenicol adverse effects
causes Gray baby syndrome in infants due to incomplete hepatic development characterized by cyanosis and cardiovascular collapse, bone marrow suppression, anemia, and pancytopenia (may be fatal), drug-drug interactions may increase levels of warfarin and phenytoin
Macrolides MOA
Bacteriostatic protein synthesis inhibitor which irreversibly binds to the 50S subunit in bacterial ribosomes and inhibit translocation steps in protein synthesis. Include erythromycin, clarithromycin, and azithromycin.
Erythromycin antibacterial spectrum
active against gram-positive bacteria but resistance is increasing
Clarithromycin antibacterial spectrum
active against gram-positive bacteria and has better activity than erythromycin against H. influenzae, Chlamydia, Legionella, and Moraxella, also used for the treatment of Helicobacter pylori
Azithromycin antibacterial spectrum
active against atypical respiratory infections including Mycoplasma pneumoniae and Legionella infection, Mycobacterium avium complex (associated with AIDS), strep pharyngitis in penicillin allergic patients and is drug of choice for chlamydial STI
Erythromycin administration
administered as enteric-coated tablets with good bioavailability, not given IV which is associated with a high incidence of thrombophlebitis (no CNS penetration)
Azithromycin administration
administered orally without food and is stable in stomach acid without enteric-coating (food decreases absorption), also available in IV formulation, has the longest half-life of all the macrolides - relatively short abx. course required (no CNS penetration)
Clarithromycin administration
administered orally or through IV and dose adjustment is required for renal impairment because it is eliminated by the kidneys (other macrolides are excreted in the bile), no CNS penetration
Macrolides adverse effects
well tolerated with the most common adverse effect being GI upset (least common with azithromycin), jaundice resulting from cholestatic hepatitis may develop with erythromycin (avoid in patients with hepatic dysfunction)
Macrolides drug-drug interactions
interfere with CYP3A4 and inhibit hepatic metabolism of several drugs including atorvastatin, simvastatin, carbamazepine, warfarin, theophylline, etc.
Clindamycin MOA
A lincosamide which inhibits peptidyl transfer by binding to the 50S ribosomal subunit and is bacteriostatic.
Clindamycin antibacterial spectrum
has narrow spectrum activity against gram-positive cocci including MRSA and anaerobes including B. fragilis
Clindamycin administration
administered orally or IV as well as topical
Clindamycin clinical use
used to treat anaerobic bacterial infections as well as MRSA-associated skin and dental infections (penetrates abscesses)
Clindamycin adverse effects
diarrhea, nausea, vomiting, penicillin-like rash, and is a major cause of C. diff. pseudomembranous colitis
Linezolid MOA
Protein synthesis inhibitor that binds to the 50S ribosomal subunit of bacteria and prevents initiation of protein synthesis. Mostly bacteriostatic but can be bactericidal to streptococci and C. perfringens.
Linezolid antibacterial spectrum
has very narrow spectrum activity against resistant gram-positive cocci such as MRSA and VRE
Linezolid administration
administered orally or through IV, no renal dose adjustment required
Linezolid adverse effects
causes dose-dependent thrombocytopenia, potentiation of serotonin syndrome when used in combination with many anti-depressants
Streptogramins MOA
bactericidal protein synthesis inhibitor that consists of two components (quinupristin/dalfopristin) that bind to a separate site on the 50S ribosomal subunit and synergistically interrupt protein synthesis.
Streptogramins antibacterial spectrum
has relatively narrow spectrum activity against gram-positive aerobic bacteria and is only used for treatment of MRSA and VRE
Streptogramins administration
administered through IV and undergoes hepatic metabolism and excretion in the feces
Streptogramins adverse effects
arthralgia and myalgia
Why is a single higher daily dose of aminoglycosides better than multiple lower doses given at timed intervals throughout the day?
a single higher dose per day is less toxic because the concentration is above the toxicity threshold for a shorter amount of time than if three lower doses were administered at timed intervals throughout the day
Fluoroquinolones MOA
bind to topoisomerase IV and DNA gyrase enzymes which inhibits DNA replication, bactericidal
Fluroquinolones administration
administered orally or through IV (bioavailability equivalent), ciprofloxacin is dosed twice daily whereas levofloxacin and moxifloxacin are dosed once daily. Ciprofloxacin and levofloxacin require dose adjustment for renal impairment due to renal elimination.
1st generation fluoroquinolone
norfloxacin
2nd generation fluoroquinolone
ciprofloxacin
3rd generation fluoroquinolone
levofloxacin
4th generation fluoroquinolone
moxifloxacin
Ciprofloxacin antibacterial spectrum
has broad spectrum activity against gram-negative bacteria including Pseudomonas aeruginosa, staphylococci (MSSA), and atypical bacterial including chlamydia, mycoplasma, and legionella
Levofloxacin antibacterial spectrum
has slightly less gram-negative activity than ciprofloxacin but has better activity against strep pneumoniae and atypicals, active against Pseudomonas aeruginosa
Moxifloxacin antibacterial spectrum
same activity as 2nd and 3rd generation fluoroquinolones as well as activity against anaerobes (has poor activity against Pseudomonas aeruginosa)
Fluoroquinolones adverse effects
causes mild GI effects such as nausea, vomiting, and diarrhea as well as headache, dizziness, and insomnia. May cause confusion in the elderly. Causes phototoxicity, neuromuscular blockade, and increased risk of tendinopathy and rupture. Can also cause QT prolongation in patients who are predisposed to arrhythmias or on other medications that may prolong QT interval.
Fluoroquinolones contraindications
in patients with Myasthenia gravis, in pregnancy, and in children (due to articular cartilage erosion)
Fluoroquinolones drug-drug interactions
may raise serum concentration of warfarin and cyclosporine
Ciprofloxacin clinical uses
pyelonephritis, UTIs, abdominal infections, prostatitis, traveler’s diarrhea, bone/joint infections, diabetic infections, skin infections, bite wounds, anthrax, Pseudomonas infections in CF, poor coverage against pneumococci, no MRSA coverage
Levofloxacin clinical uses
same as cipro but has better activity against Strep pneumo, often used for respiratory infections
Moxifloxacin clinical uses
same as cipro but has better activity against strep pneumo and anaerobes, often used for respiratory infections, no Pseudomonas coverage
Nitrofurantoin MOA
involves the bacterial conversion of drug to highly reactive intermediates that react nonspecifically with many targets (ribosomal targets, synthetic machinery of proteins, RNA, DNA, and metabolic enzymes, bactericidal
Nitrofurantoin antibacterial spectrum
bactericidal against many gram-positive and gram-negative bacteria
Nitrofurantoin clinical use
used for empiric treatment of uncomplicated cystitis (UTI), concentrates in urine but does not have good tissue distribution
Nitrofurantoin adverse effects
anorexia, nausea, and vomiting as well as neuropathies and hemolytic anemia in patients with glucose-6-phosphate-dehydrogenase deficiency, also associated with interstitial pulmonary fibrosis
Nitrofurantoin contraindications
patients with renal impairment
Metronidazole MOA
activated by a single reduction step by the bacteria which forms radicals and reacts with nucleic acids, damaging DNA and leads to cell death
Metronidazole antibacterial spectrum
bactericidal under anaerobic conditions against Bacteroides difficile (formerly Clostridium), Helicobacter pylori (part of a multi-drug regimen)
Metronidazole clinical uses
used to treat a wide variety of anaerobic infections including trichomoniasis, SSSIs, bone and joint infections, endocarditis, gynecologic infections, intra-abdominal infections, lower respiratory tract infections, systemic anaerobic infections, and traveler’s diarrhea
Metronidazole adverse effects
most common is GI upset but can also cause a Disulfiram-like reaction with ethanol (flushing, tachycardia, and hypotension)
What is the first-line treatment for non-severe (C. difficile infection) CDI?
Oral vancomycin (bacteriostatic against C. difficile)
What is the second-line treatment for non-severe CDI?
Oral fidaxomicin - a macrolide (bactericidal against C. difficile)
What is the third-line treatment for non-severe CDI if allergy to vancomycin or fidaxomicin?
Oral metronidazole (bacteriostatic against C. difficile)
Sulfonamides MOA
inhibit folate metabolism (synthetic analog of PABA)
Trimethoprim MOA
inhibits the enzyme dihydrofolate reductase
What is the advantage of combining sulfamethoxazole with trimethoprim (Bactrim- TMP/SMX)
sulfamethoxazole works synergistically with trimethoprim making the combination bactericidal whereas each drug alone is bacteriostatic and require host defenses to clear infection
TMP/SMX antibacterial spectrum
(treatment for UTIs) active against H. influenzae, Legionella (in URIs but does not cover Strep pneumo), Salmonella (excellent biliary tree penetration), Pneumocystitis Jirovecii, Listeria monocytogenes (in combination with amoxicillin), and Toxoplasmosis
TMP/SMX adverse effects
hypersensitivity reactions including rash and Stevens-Johnson Syndrome (rare), neonatal kernicterus (Sulfa), hyperkalemia, megaloblastic anemia, leukopenia, thrombocytopenia (TMP), and hemolytic anemia may occur in patients with glucose-6-phosphate-dehydrogenase deficiency (sulfa)
TMP/SMX drug-drug interactions
warfarin, phenytoin, and methotrexate
TMP/SMX contraindications
in newborns, pregnant women, and patients with renal disease
TMP/SMX administration
typically administered orally but can also be given through IV for treatment of severe pneumonia caused by P. jirovecii
Rifaximin MOA
inhibits RNA polymerase and is bacteriostatic, minimally effects CYP
Rifampin MOA
inhibits RNA polymerase and is bactericidal, powerful inducer of many CYPs known
Rifaximin clinical uses
treatment of traveler’s diarrhea, hepatic encephalopathy, IBS/SIBO
Rifaximin adverse effects
peripheral edema, nausea, and rash
Rifampin clinical uses
oral treatment of Mycobacterium tuberculosis (can not be used alone due to rapid resistance) and MRSA
Rifampin adverse effects
hepatoxicity, GI upset, rash, orange-red tears, saliva, urine, and sweat, has a large capacity for drug-drug interactions due to the induction of multiple CYPs in liver
Isoniazid MOA
inhibits the synthesis of mycolic acids which are essential components of mycobacterial cell walls
Isoniazid antibacterial spectrum
bactericidal against actively growing tubercle bacilli and less effective against nontuberculous mycobacteria, penetrates into macrophages and is active against both intracellular and extracellular organisms
Isoniazid administration
administered orally along with pyridoxine to prevent peripheral neuropathy, no dose adjustment required for renal impairment
Isoniazid clinical uses
can be paired with rifampin to treat most strains of tuberculosis (however a four-drug combo is usually used for first two months of treatment - referred to as ‘intensive phase’)
Isoniazid adverse effects
hepatotoxicity/hepatitis is most serious effect, rash, fever, and neuropathy
Ethambutol MOA
inhibits mycobacterial arabinosyl transferases which are essential enzymes that function in the synthesis of the mycobacterial cell wall
Ethambutol administration
always administered in combination with other anti-TB drugs to prevent resistance
Ethambutol antibacterial adverse effects
optic neuritis which results in diminished visual acuity and loss of ability to discriminate between red and green, the risk of optic neuritis increases with higher doses and in patients with renal impairment
