cataataca's version from 2015-04-14 21:37

Mecanismos de acción antibióticos


Betalactámicos, Penicilinas
Question Answer
Grupos incluidos en los betalactámicoscarbapenems, cefalosporinas, penicilinas
Mx de ax de los betalactámicosinhibición de la síntesis de peptidoglicanos
Mx resistencia bacteriana a betalactámicosmodificación PBP (Menor afinidad a betalactámicos), inhabilidad del fármaco para llegar al sitio de acción debido a impermeabildiad membrana externa de Gramnegativas (se necesita de porinas por las cualtes atb pequeños hidrofílicos pueden pasar, Pseudomonas aeruginosa es resistente a muchos atbs pues no tiene estas porinas), presencia bombas de eflujo (Pseudoomonas, E. coli, N. gonorrhoaea, producción y secreción betalactamasas, biopelículas
Espectro activdiad atb de penicilinas G y Vhighly active against sensitive strains of gram-positive cocci, but they are readily hydrolyzed by penicillinase. Thus they are ineffective against most strains of S. aureus
Espectro penicilinas resistentes a penicilinasas less potent antimicrobial activity against microorganisms that are sensitive to penicillin G, but they are the agents of first choice for treatment of penicillinase-producing S. aureus and S. epidermidis that are not methicillin resistant
Penicilinas resistentes a penicilinasasmeticilina, nafcillin, oxacillin, cloxacillin and dicloxacillin
Espectro Ampicilina, amoxicilina (aminopenicilinas)antimicrobial activity is extended to include such gram-negative microorganisms as Haemophilus influenzae, E. coli, and Proteus mirabilis, Listeria monocytogenes. Frequently these drugs are administered with a -lactamase inhibitor such as clavulanate or sulbactam to prevent hydrolysis by class A -lactamases. Penicillin-resistant strains should be considered ampicillin/amoxicillin-resistant
Espectro carbenicillin (discontinued in the U.S.), its indanyl ester (carbenicillin indanyl), and ticarcillin (marketed only in combination with clavulanate in the U.S.)extended to include Pseudomonas, Enterobacter, and Proteus spp. These agents are inferior to ampicillin against gram-positive cocci and Listeria monocytogenes and are less active than piperacillin against Pseudomonas.
Espectro Mezlocillin, azlocillin (both discontinued in the U.S.), and piperacillinexcellent antimicrobial activity against many isolates of Pseudomonas, Klebsiella, and certain other gram-negative microorganisms. However, the emergence of broad-spectrum beta-lactamases is threatening the utility of these agents. Piperacillin retains the activity of ampicillin against gram-positive cocci and L. monocytogenes.
Concentración penicilinas en LCR<1% of those in plasma when the meninges are normal, When there is inflammation, concentrations in CSF may increase to as much as 5% of the plasma value
Vida media y excreción penicilina G eliminated rapidly, particularly by glomerular filtration and renal tubular secretion, such that their half-lives in the body are short, typically 30-90 minutes. Approximately 10% of the drug is eliminated by glomerular filtration and 90% by tubular secretion (penicillin G) therefore in prematures and neonnates the half life is considerably longer vs adults.

Algunas indicaciones farmacológicas de las penicilinas

Question Answer
Fármaco de elección para infecciones causadas por S. pneumoniae sensible a penicilinapenicilina G
Tto faringitis estreptocócicaThe preferred oral therapy is with penicillin V, 500 mg every 6 hours for 10 days. Penicillin therapy of streptococcal pharyngitis reduces the risk of subsequent acute rheumatic fever; however, current evidence suggests that the incidence of glomerulonephritis that follows streptococcal infections is not reduced to a significant degree by treatment with penicillin
Resistencia S. aureus metilino resistente nosocomialresistant to penicillin G, all the penicillinase-resistant penicillins, and the cephalosporins (aminoglycosides, tetracyclines, erythromycin, and clindamycin as well). Vancomycin, linezolid, quinupristin-dalfopristin, and daptomycin are active for infections caused by these bacteria, although reduced susceptibility to vancomycin has been observed
Tto de elección para Neisseria meningitidis o meningococcoPenicillin G remains the drug of choice for meningococcal disease. Patients should be treated with high doses of penicillin given intravenously
Tto elección para infecciones gonocócicas (Neisseria gonorrhoeae) Gonococci gradually have become more resistant to penicillin G, and penicillins are no longer the therapy of choice. Uncomplicated gonococcal urethritis is the most common infection, and a single intramuscular injection of 250 mg ceftriaxone is the recommended treatment. Gonococcal arthritis, disseminated gonococcal infections with skin lesions, and gonococcemia should be treated with ceftriaxone 1 g daily given either intramuscularly or intravenously for 7-10 days
Tto sífilisTherapy of syphilis with penicillin G is highly effective. Primary, secondary, and latent syphilis of <1-year duration may be treated with penicillin G procaine (2.4 million units per day intramuscularly) plus probenecid (1.0 g/day orally) for 10 days or with 1-3 weekly intramuscular doses of 2.4 million units of penicillin G benzathine (three doses in patients with HIV infection).
Tto sífilis congénitotreated for at least 10 days with 50,000 units/kg daily of aqueous penicillin G in two divided doses or 50,000 units/kg of procaine penicillin G in a single daily dose
Tto MRSA nosocomialVancomycin is considered the drug of choice for such infections, although intermediate-level resistance is emerging. Some physicians use a combination of vancomycin and rifampin, especially for life-threatening infections and those involving foreign bodies
Indicacions aminopenicilinas en infecciones respiratorias del TRSAmpicillin and amoxicillin are active against S. pyogenes and many strains of S. pneumoniae and H. influenzae, which are major upper respiratory bacterial pathogens. The drugs constitute effective therapy for sinusitis, otitis media, acute exacerbations of chronic bronchitis, and epiglottitis caused by sensitive strains of these organisms. Amoxicillin is the most active of all the oral -lactam antibiotics against both penicillin-sensitive and penicillin-resistant S. pneumoniae. Bacterial pharyngitis should be treated with penicillin G or penicillin V because S. pyogenes is the major pathogen.
Indicaciones piperacilinaPiperacillin and related agents are important agents for the treatment of patients with serious infections caused by gram-negative bacteria. Such patients frequently have impaired immunological defenses, and their infections often are acquired in the hospital. Therefore, these penicillins find their greatest use in treating bacteremias, pneumonias, infections following burns, and urinary tract infections owing to microorganisms resistant to penicillin G and ampicillin; the bacteria especially responsible include P. aeruginosa, indole-positive strains of Proteus, and Enterobacter spp. Because Pseudomonas infections are common in neutropenic patients, therapy for severe bacterial infections in such individuals should include a -lactam antibiotic such as piperacillin with good activity against these microorganisms


Question Answer
No son útiles ante los siguientes patógenospenicillin-resistant S. pneumoniae, MRSA, methicillin-resistant S. epidermidis and other coagulase-negative staphylococci, Enterococcus, L. monocytogenes,Legionella pneumophila, L. micdadei, C. difficile, Xanthomonas maltophilia, Campylobacter jejuni, KPC-producing Enterobacteriaceae, and Acinetobacter spp.
Cefalosporinas de primera generacióncefapirina, cefadroxilo, cefatrizina, cefradina, cefaloridina, cefazolina, fecalexina, cefalotina
Cefalosporinas de segunda generacióncefuroxime, cefaclor, cefotetan, loracarbe, cefmetazola, cefamandola
Cefalosporinas de tercera generaciónceftriaxona, cefixime, cefotaxime, ceftazidime, moxalactam, cefoperazona
Cefalosporinas de IV generacióncefepime, cefpiroma, flumoxel
Cefalosporinas de V generaciónceftobripole
Espectro cefalosporinas de I generaciónhave good activity against gram-positive bacteria and relatively modest activity against gram-negative microorganisms. Most gram-positive cocci (with the exception of enterococci, methicillin-resistant S. aureus, and S. epidermidis) are susceptible. Most oral cavity anaerobes are sensitive, but the B. fragilis group is resistant. Activity against Moraxella catarrhalis, E. coli, K. pneumoniae, and P. mirabilis is good.
Espectro cefalosporinas II generaciónsomewhat increased activity against gram-negative microorganisms but are much less active than the third-generation agents. A subset of second-generation agents (cefoxitin, cefotetan, and cefmetazole, which have been discontinued in the U.S.) also is active against the B. fragilis group.
Espectro cefalosporinas III generación generally are less active than first-generation agents against gram-positive cocci; these agents are much more active against the Enterobacteriaceae, although resistance is dramatically increasing due to -lactamase-producing strains. A subset of third-generation agents (ceftazidime and cefoperazone, which are discontinued in the U.S.) also is active against P. aeruginosa but less active than other third-generation agents against gram-positive cocci
Espectro cefalosporinas IV generaciónsuch as cefepime, have an extended spectrum of activity compared with the third generation and have increased stability from hydrolysis by plasmid and chromosomally mediated -lactamases (but not the KPC class A -lactamases). Fourth-generation agents are useful in the empirical treatment of serious infections in hospitalized patients when gram-positive microorganisms, Enterobacteriaceae, and Pseudomonas all are potential etiologies.
Vía administración cefalosporinasCephalexin, cephradine, cefaclor, cefadroxil, loracarbef, cefprozil, cefpodoxime proxetil, ceftibuten, and cefuroxime axetil are absorbed readily after oral administration. Cefdinir and cefditoren are also effective orally. The other cephalosporins can be administered intramuscularly or intravenously.
Excreción cefalosporinasexcreted primarily by the kidney; thus the dosage should be altered in patients with renal insufficiency. Probenecid slows the tubular secretion of most cephalosporins. Exceptions are cefpiramide and cefoperazone, which are excreted predominantly in the bile (neither is available in the U.S.).
Distribución de las cefalosporinasSeveral cephalosporins penetrate into the CSF in sufficient concentration to be useful for the treatment of meningitis. These include cefotaxime, ceftriaxone, and cefepime (see "Therapeutic Uses" section). Cephalosporins also cross the placenta, and they are found in high concentrations in synovial and pericardial fluids. Penetration into the aqueous humor of the eye is relatively good after systemic administration of third-generation agents, poorly in vitrous


Question Answer
Estructura generalfused -lactam ring and a five-member ring system that differs from the penicillins because it is unsaturated and contains a carbon atom instead of the sulfur atom
Mx de acciónbinds to penicillin-binding proteins, disrupts bacterial cell wall synthesis, and causes death of susceptible microorganisms. They are very resistant to hydrolysis by most -lactamases
Espectro Imipenemwide variety of aerobic and anaerobic microorganisms. Streptococci (including penicillin-resistant S. pneumoniae), enterococci (excluding E. faecium and non--lactamase-producing penicillin-resistant strains), staphylococci (including penicillinase-producing strains), and Listeria all are susceptible. Although some strains of methicillin-resistant staphylococci are susceptible, many strains are not. Activity was excellent against the Enterobacteriaceae until the emergence of KPC (Klebsiella pneumoniae carbapenemasa producing strains). Most strains of Pseudomonas and Acinetobacter are inhibited. S. maltophilia is resistant. Anaerobes, including B. fragilis, are highly susceptible.
Rx adversas ImipenemNausea and vomiting are the most common adverse reactions (1-20%). Seizures also have been noted in up to 1.5% of patients, especially when high doses are given to patients with CNS lesions and to those with renal insufficiency. Patients who are allergic to other -lactam antibiotics may have hypersensitivity reactions when given imipenem.
Utilidad uso concomitante cilastatinapara carbapenems sensibles a dipeptidasa renal como imipenem
Indicaciones terapéuticas Imipeneminfex nosocomiales por bacterias resistentes a cefalosporinas como Enterobacter spp. (con excepcion de KCP). Es útil en ptes con infex graves q recibieron recientemente betalactámicos por el riesgo q ellos tienen de infex x bacterias resistentes a penicilinas y/o cefalosporinas. No debe usarse como monoterapia para P. aeruginosa por el riesgo de desarrollo de resistencia.
Espectro meropenemactivity against some imipenem-resistant P. aeruginosa but less activity against gram-positive cocci. Clinical experience with meropenem demonstrates therapeutic equivalence with imipenem.
Espectro e indicaciones de Ertapenemlonger t1/2 that allows once-daily dosing and by having inferior activity against P. aeruginosa and Acinetobacter spp. Its spectrum of activity against gram-positive organisms, Enterobacteriaceae, and anaerobes makes it attractive for use in intra-abdominal and pelvic infections


Question Answer
Estructurabetalactámico monocíclico
Espectroactivity only against gram-negative bacteria; it has no activity against gram-positive bacteria and anaerobic organisms. However, activity against Enterobacteriaceae is excellent, as is that against P. aeruginosa
Farmacodinamia y farmacocinéticaposología intramuscularly or intravenously, t1/2 for elimination is 1.7 hours, and most of the drug is recovered unaltered in the urine. The t1/2 is prolonged to ~6 hours in anephric patients
Reacción hipersensibilidad cruzada con otros betalactámicosallergic to penicillins or cephalosporins appear not to react to aztreonam, with the exception of ceftazidime