1 - SYSTEMIC ANTIBACTERIAL AGENTS Flashcards
Owing to the increased prevalence of uncomplicated skin and soft tissue infections (USSTI) caused by community-acquired MRSA, there has been changes to the antibiotic prescribing pattern such that there is increase use of doxycycline, minocycline and bactrim (trimethoprim-sulfamethoxazole), and a decrease in the use of oral cephalosporin therapy
True
Penicillins are bactericidal and inhibit synthesis of the bacterial cell wall
True
Cephalosporins are bactericidal and inhibit synthesis of the bacterial cell wall
True
Combination Beta-lactams (penicillins) and beta-lactamase inhibitor antibiotics are bactericidal and inhibit synthesis of the bacterial cell wall
True (amoxicillin-clavulanate, ticarcillin-clavulanate, piperacillin-clavulanate)
Vancomycin is both bactericidal (against staphylococci and streptococci) and bacteriostatic (against most enterococci) against gram +Ve organisms only and inhibits synthesis of the bacterial cell wall
True
Macrolides (clarithromycin, erythromycin, azithromycin) are bacteriostatic against most gram +Ve organisms except MRSA and enterococcus, as they inhibit bacterial protein synthesis
True
Fluoroquinolones are bactericidal against most gram -Ve organisms pseudomonas, enterobacteriaceae, bacillus anthrax (ciprofloxacin) and variable efficacy against gram +Ve organisms staph aureus and strep pyogenes (levofloxacin, moxifloxacin) by interfering with bacterial DNA replication
True
Tetracyclines (tetracycline, doxycycline, minocycline) are bacteriostatic in that they possess greater gram +Ve than gram -Ve activity by inhibiting bacterial protein synthesis
True (binding to 30s subunit of the bacterial ribosome)
Rifampicin (a rifamycin antibiotic) is bactericidal with activity against mycobacteria and gram +Ve organisms and poor gram -Ve coverage by preventing bacterial protein synthesis
True
The folate-synthesis inhibitor bactrim (trimethoprim-sulfamethoxazole) is bacteriostatic against many gram +Ve cocci, pseudomonas and PCP by inhibiting bacterial protein synthesis
True
The Lincosamide Clindamycin is bacteriostatic against several gram +Ve cocci and a wide variety of anaerobes by reducing bacterial protein synthesis
True
Penicillin G (IV and IM) and Penicillin V (PO) are first generation natural penicillins (bactericidal) with activity against gram +Ve cocci and rods, gram -Ve cocci and anaerobes, but are ineffective against MSSA and MRSA
True (dicloxacillin, nafcillin, oxacillin are semi-synthetic first generation penicillins)
Dicloxacillin, nafcillin, oxacillin are semi-synthetic first generation beta-lactamase resistant penicillins (bactericidal) exhibit activity against MSSA and other gram +Ve cocci such as streptococcus pyogenes, but MRSA developed subsequently
True (penicillin G and penicillin V are natural first generation penicillins)
Amoxicillin and ampicillin (aminopenicillins) are second generation penicillins (bactericidal) with extended activity against gram -Ve bacilli
True
Ticarcillin (carboxypenicillin) is a third generation extended spectrum penicillin (bactericidal) with anti-pseudomonal activity
True
Piperacillin (ureidopenicillin) is a fourth generation extended spectrum penicillin (bactericidal) with anti-pseudomonal activity
True
Amoxicillin-clavulanate and ampicillin-sulbactam are combination second generation/beta-lactamase inhibitors (bactericidal)
True
Ticarcillin-clavulanate is a combination third generation carboxypenicillin/beta-lactamase inhibitor (bactericidal)
True
Piperacillin-tazobactam is a fourth generation ureidopenicillin/beta-lactamase inhibitor (bactericidal)
True
Staph aureus (gram +Ve coccus) and many enterobacteriaceae (gram -Ve rods) species bacteria produce beta-lactamase enzyme which hydrolyses beta-lactam penicillins (first generation semi-synthetic penicillins Dicloxacillin, nafcillin and oxacillin are beta-lactamase resistant), rendering these antibiotics ineffective
True (therefore some beta-lactam penicillins have been combined with a beta-lactamase inhibitor to produce resistance of the antibiotics to degradation by beta-lactamase enzyme)
All beta-lactams (penicillins and cephalosporins) are excreted renally except nafcillin, oxacillin and piperacillin
True (nafcillin, oxacillin and piperacillin are eliminated through the biliary system)
Beta-lactams (penicillins and cephalosporins) are more commonly associated with drug-induced hypersensitivity reactions with the severity ranging from exanthematous eruptions, to urticarial eruptions to fatal anaphylaxis
True (Penicillin G is the first reported to cause a hypersensitivity reaction, with amoxicillin most commonly implicated agent more recently)
A skin eruption that is not truly allergic in origin may arise when ampicillin is given to patients with infectious mononucleosis or lymphocytic leukaemia or when it is co-administered with allopurinol, therefore this unique ampicillin eruption is not believed to be a contraindication to treatment with other penicillins at a later date
True (the eruption is generalised, maculopapular and pruritic, and typically manifests within 7-10 days after the initiation of ampicillin with usual persistence for up to 1 week after ampicillin in discontinued)
In patients with a history of severe and life-threatening allergic reaction to a penicillin or cephalosporin, avoidance of the other drugs in these 2 general categories is advised
True (for practical purposes it should be assumed that all penicillins cross-react, and that if they have a true allergic reaction to one form of penicillin they may react to all penicillins and possibly to cephalosporins as well)
The aminopenicillins (amoxicillin and ampicillin) appear to be associated with a higher incidence of allergic reactions than other penicillins
True
GI upset including nausea and antibiotic-associated diarrhoea are not uncommon with penicillins
True (yoghurt or other means of lactobacillus ingestion may be a helpful adjuvant to prevent diarrhoea-related complications due to alterations in normal gut flora)
C. diff colitis can occur with penicillins
True
Shore nails (transverse leuconychia and onychomadesis/nail shedding following drug-induced erythroderma) have been seen with Dicloxacillin
True
Onychomadesis (nail shedding) and photo-onycholysis have been noted following dicloxacillin use
True
Cholestasis associated with penicillins is uncommon
True
Probenecid prolongs the renal excretion of penicillin and penicillin-beta lactamase antibiotics
True (result in an increase in serum concentration due to delayed renal excretion)
Oral antibiotics including beta-lactams (penicillins and cephalosporins) may potentially alter the anticoagulant effects of warfarin
True
Penicillins and cephalosporins are beta-lactam antibiotics
True
As oppose to penicillins which are also beta-lactams, the structure of beta-lactam cephalosporins gives it resistance to beta-lactamase enzymes
True
There are 5 generations of cephalosporins (beta-lactams) based on their general spectrum of antimicrobial activity
True
Cefazolin (IM/IV) and cephalexin (PO) are first generation cephalosporins which are most active of all the cephalosporins against gram +Ve staphylococci and non-enterococcal streptococci, and are active against many of the oral anaerobes except the Bacteroides fragilis group
True
Cefazolin (IM/IV) and cephalexin (PO) are first generation cephalosporins which are resistant to MRSA, streptococcus pneumoniae and gram -Ve organisms (haemophilus influenzae and enterococci, pseudomonas) and nosocomial gram -Ve infections
True
Cefuroxime (IV/IM/PO) and cefaclor (PO) are second generation true cephalosporins which demonstrate increased gram -Ve activity (against haemophilus influenzae, moraxella catarrhalis, neisseria meningitidis, neisseria gonorrhoea and some enterobacteriacea) and decreased gram +Ve activity
True (second generation cephamycins such as cefoxitin IV/IM are not ‘true’ cephalosporins and have inferior activity against gram +Ve staph and strep, but are effective against Bacteroides fragilis)
Third, forth and fifth generation cephalosporins have anti-pseudomonal activity
True
Third generation cephalosporins demonstrate less consistent activity against gram +Ve organisms and an increased spectrum of gram -Ve activity due to beta-lactamase stability, and some have anti-pseudomonal activity
True
Fifth generation cephalosporins have shown activity against MRSA, VRSA and MSSA and pseudomonas
True
Cephalexin (first generation cephalosporin) is best absorbed from an empty stomach
True
The bioavailability of Cefuroxime (second generation cephalosporin) is increased when taken with food
True (in contrast with first generation cephalosporin cephalexin where it is best absorbed from an empty stomach)
First and second generation cephalosporins including cephalexin are excreted primarily by the kidneys and dosage adjustments are recommended for patients with significant renal insufficiency
True
The short half life of cephalexin (less than 1 hour) may be associated with bacterial resistance if given less than TDS or QID dosing
True
GI effects such as nausea, vomiting, diarrhoea are relatively frequent with cephalosporins; although unlike its beta-lactam counterpart penicillins, antibiotic-associated C. diff colitis is much less common
True
Mild elevation of liver transaminases may occur with cephalosporins, although serious hepatic injury is rare
True
Potential cross-reactivity of cephalosporins with penicillins has been traditionally stated to occur in 5-10% of penicillin-allergic individuals, and cephalosporin-allergic reactions occur more commonly in patients with a history of penicillin allergy vs those without penicillin allergy
True (the degree of cross-reactivity likely depends on the generation of cephalosporin and very likely is due to the structural similarities/differences with penicillins I.e. In early first generation cephalosporins which sometimes contain trace amounts of penicillins)
Cephalosporin use should be avoided in patients with a history of an immediate or accelerated reaction to penicillin (IgE-mediated or severe type IV delayed hypersensitivity reactions)
True (cephalosporin skin testing is much less reliable than penicillin skin testing to evaluate hypersensitivity reactions)
Cephalosporin may cause vaginal candidiasis
True
Acute paronychia has been described following treatment with cephalexin
True
Drug-induced immune-mediated haemolytic anaemia have been associated with ceftriaxone (third generation cephalosporin) and piperacillin (forth generation penicillin)
True
Nephrotoxicity is rare in cephalosporins, but dose reduction of most cephalosporins is recommended in patients with renal insufficiency
True
Cephalosporins (such as the cephamycin antibiotic cefotetan) with the NMTT ring have been reported to induce a disulfiram-like reaction with alcohol ingestion
True
Cephalosporins (such as the cephamycin antibiotic cefotetan) with the NMTT ring can also prolong prothrombin times as it inhibits production of vitamin-K clotting factors and could be an issue in patients on anticoagulation therapy such as warfarin
True
Probenecid competes with renal tubular secretion of some cephalosporins and may increase and prolong the plasma levels for cephalosporins
True
Some cephalosporins may increase the risk of nephrotoxicity when co-administered with aminoglycosides (gentamicin) or potent diuretics
True
In patients with renal impairment, the half-life of beta-lactam/beta-lactamase combination of drugs is prolonged and blood levels are elevated, thus warranting dosage adjustment in some cases
True
The recommended oral agent for the treatment of animal or human bites infected by combined aerobic and anaerobic pathogens is amoxicillin-clavulanate
True
Adverse effects most often associated with amoxicillin-clavulanate and piperacillin-tazabactam are GI effects especially diarrhoea
True (diarrhoea occurs less frequently when amoxicillin-clavulanate is administered with food)
Hypersensitivity reactions from the beta-lactam/beta-lactamase antibiotics are similar to those seem from the beta-lactam (penicillins and cephalosporins) antibiotics alone
True
Ticarcillin and piperacillin can prolong bleeding times and cause platelet aggregation dysfunction
True
Ticarcillin and piperacillin can cause hypernatraemia, transient elevation of transaminases, thrombocytopenia, neutropenia and eosinophilia
True
Carbapenems (imipenem) demonstrate the most complete range of antibacterial coverage of any antibiotic class
True
There is a high degree of cross-reactivity between Carbapenems (imipenem) and penicillin
True (the incidence of allergic-type reactions to a carbapenem is 5.2 times greater in patient who were reportedly allergic to penicillin)
Monobactams (aztreonam) has an antibacterial spectrum activity limited to aerobic gram -Ve organisms and has been employed as a sole agent in treating gram -Ve cutaneous infections in conjunction with other drugs that inhibit gram +Ve or anaerobic flora
True
Monobactams (aztreonam) has an adverse effect profile similar to that of other beta-lactam antibiotics (penicillins and cephalosporins) including rare cases of erythema multiforme, TEN, urticarial eruptions and exfoliative dermatitis
True (however patients who are allergic to penicillin can be safely given aztreonam)
Patients who are allergic to penicillin can be safely given aztreonam
True
Vancomycin is clinically important in the treatment of MRSA
True
Vancomycin is administered IV because of minimal absorption from the GI tract and is used PO only for the treatment of C. Diff diarrhoea
True
90-100% of vancomycin is excreted by glomerular filtration in the kidneys, therefore dosage modification is recommended in patients with marked renal insufficiency
True
Red man syndrome and shock secondary to histamine release can be caused by rapid transfusion of vancomycin
True
Vancomycin is one of the most common causes of drug-induced linear IgA bullous dermatosis, developing after the initiation of vancomycin and also upon re-challenge
True (as vancomycin may rarely cause TEN, differentiation of TEN from vancomycin-induced linear IgA bullous dermatosis needs to be differentiated as multiple cases of vancomycin-induced linear IgA bullous dermatosis have been reported as these have presented as exanthematous eruption without blistering)
Vancomycin dose-related hearing loss/ototoxicity has been reported in patients with renal failure, likely due to reduced excretion of vancomycin leading to accumulation of the drug
True
Vancomycin has caused nephrotoxicity particularly when administered along with aminoglycoside antibiotics (gentamicin)
True
Macrolides have antibacterial and anti-inflammatory properties
True (anti-inflammatory properties contribute towards their therapeutic benefit in inflammatory facial dermatoses such as acne and Rosacea)
Erythromycin is the prototype macrolide
True (other macrolides which are in fact azalides include clarithromycin and azithromycin)
Clarithromycin and azithromycin are azalide antibiotics (class of macrolide antibiotics)
True
In the management of acne vulgaris, the use of oral erythromycin has markedly declined due to the widespread emergence of resistant P. acnes strains, with resistance rates as high as 50%
True
PO erythromycin has an erratic oral bioavailability and a short half-life requiring frequent administration
True
PO erythromycin is associated with frequent GI adverse effects such as nausea, abdominal discomfort and diarrhoea
True (erythromycin binds to motilin receptors throughout the GI tract, releasing motilin which stimulates migrating digestive contractions thus inducing a higher incidence of GI disturbance than with the azalide subcategory)
Erythromycin (and to a lesser extent clarithromycin) is a CYP3A4 and CYP1A2 inhibitor which leads to reduced clearance and increased risk of toxicity of a wide variety of drugs
True
Clarithromycin is 2-4 times more potent than erythromycin against gram +Ve organisms such as staphylococci and streptococci
True
Unlike erythromycin, clarithromycin and azithromycin possess increased activity against several gram -Ve pathogens including H. Influenzae
True
Both clarithromycin and azithromycin are affective against atypical mycobacteria such as Mycobacterium avium-intracellulare, Mycobacterium Leprae, and Mycobacterium chelonei
True (Clarithromycin is most effective against M. Leprae which causes leprosy)
Both clarithromycin and azithromycin demonstrate activity against Toxoplasma gondii, Treponema pallidum (cause of syphilis) and Borrelia burgdoferi
True
Azithromycin also has activity against organisms contracted from animal bites and human bites
True (similar to amoxicillin-clavulanate)
Azithromycin has activity against E. Coli, N. Gonorrhoea, chlamydia trachomatis
True
Unless administered in an enteric coated form, erythromycin is vulnerable to gastric acid inactivation and must be taken on an empty stomach
True
Clarithromycin and azithromycin (azalides class of macrolide antibiotics) have improved bioavailability than erythromycin with clarithromycin equally well absorbed with or without food, although azithromycin absorption in decreased with food
True
Both clarithromycin and erythromycin are excreted by the kidneys and dosages of both drugs warrant modification in significant renal failure
True (azithromycin is primarily metabolised and eliminated in the liver and so no adjustments are necessary in renal disease)
Selective use of azithromycin for acne vulgaris and Rosacea may be helpful in some patients who are intolerant to tetracyclines
True
Erythromycin is a rare cause of reversible hearing loss at high doses
True (ototoxicity reported at higher doses or in patients with hepatic or renal dysfunction as erythromycin liver metabolism and renal elimination is reduced in these patents leading to accumulation and increased serum levels of the drug)
Erythromycin is a a rare cause of skin eruptions and allergic reactions
True
Cardiac conduction abnormalities have been associated with macrolide use, and erythromycin carried the greatest risk of QT prolongation and torsades de pointes
True (risk of Cardiotoxicity increased with advanced age, higher dosages, rapid administration, and history of cardiac disease)
Clarithromycin may cause a metallic or bitter taste
True (also fixed drug eruption, leukocytoclastic vasculitis and hypersensitivity reactions)
Azithromycin has been associated with photosensitivity
True (also irreversible deafness, angioedema, hypersensitivity reactions and contact dermatitis)
Macrolide antibiotics (erythromycin, clarithromycin, azithromycin) have been associated with cholestatic hepatitis
True
There is increased risk of hypertrophic pyloric stenosis in infants exposed to macrolides through breast feeding mothers as these drugs are secreted into breast milk
True
Amiodarone (antiarrhythmic agent) may increase serum levels of erythromycin and clarithromycin (macrolides) through CYP3A4 inhibition
True (besides being a CYP3A4 inhibitor itself, erythromycin and clarithromycin is also subjected to CYP3A4 metabolism)
Fluoxetine (SSRI antidepressant) may increase serum levels of erythromycin and clarithromycin (macrolides) through CYP3A4 inhibition
True (besides being a CYP3A4 inhibitor itself, erythromycin and clarithromycin is also subjected to CYP3A4 metabolism)
Ketoconazole, itraconazole, fluconazole (azole antifungal agents) may increase serum levels of erythromycin and clarithromycin (macrolides) through CYP3A4 inhibition
True (besides being a CYP3A4 inhibitor itself, erythromycin and clarithromycin is also subjected to CYP3A4 metabolism)
Diltiazem and verapamil (calcium channel blockers) may increase serum levels of erythromycin and clarithromycin (macrolides) through CYP3A4 inhibition
True (besides being a CYP3A4 inhibitor itself, erythromycin and clarithromycin is also subjected to CYP3A4 metabolism) -
nifedipine is not a CYP3A4 inhibitor
Macrolides (erythromycin and Clarithromycin) inhibit the first pass Cytochrome P450 system in the liver and intestines, leading to decreased metabolic clearance and raised plasma levels many drugs
True (mainly inhibit activity of CYP3A4 and to a lesser extent inhibit activity of CYP1A2)
Rifampicin (rifamycin antibacterial agents) may reduce serum levels of erythromycin and clarithromycin (macrolides) through CYP3A4 induction
True (besides being a CYP3A4 inhibitor itself, erythromycin and clarithromycin is also subjected to CYP3A4 metabolism)