Penicillins methicillin

After removal of the carboxylic acid portion of the original amide, a new amide linkage is generated, e.g. by reaction with a suitable acyl chloride. One of the first commercial semi-synthetic penicillins, methicillin, was produced as shown. Other agents, e.g. ampicillin, may be produced by similar means, though sensitive functional groups in the new side-chain will need suitable protection. 

Like other semisynthetic penicillins, methicillin exhibits an antibacterial effect similar to that of benzylpenicillin. The main difference between methicillin and benzylpenicillin is that it is not inactivated by the enzyme penicillinase, and therefore it is effective with respect to agents producing this enzyme (staphylococci). It is used for infections caused by benzylpenicillin-resistant staphylococci (septicemia, pneumonia, empyemia, osteomyelitis, abscesses, infected wounds, and others). Synonyms of this drug are cinopenil, celbenin, staphcillin, and others. 

Antistaphylococcal penicillins Methicillin [meth i SILL in], naf-cillin [naf SILL in], oxacillin [ox a SILL in], cloxacillin [klox a SILL in], and dicloxacillin [dye klox a SILL in] are penicillinase-resistant penicillins. Their use is restricted to the treatment of infections caused by penicillinase-producing staphylococci. Because of its toxicity, methicillin is rarely used. Methicillin-resistarft strains of Staphylococcus aureus (MRSA), currently a serious source of nosocomial (hospital-acquired) infections, are usually susceptible to vancomycin, and rarely to ciprofloxacin or rifampin. 

The penicillinase-resistant penicillins [methicillin, nafcillin, oxacillin, cloxacillin, and dicloxacillin] have 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. 

Numerous other penicillin sulfones have been reported to be P-lactamase inhibitors, as illustrated in Table 5. The effect of C-6 substituents has been extensively explored starting with 6-APA sulfone (25, R = NH2, R = H, R" = R " = CH ), which has modest activity. Mechanistic considerations led to preparation of sulfones of poor substrates, compounds such as methicillin, cloxaciUin, nafaciUin, and quinaciUin sulfone (25,... 

Penicillin, 2,6-dimethoxyphenyl-, methyl ester (methicillin methyl ester)... 

Methicillin — see Penicillin, 2,6-dimethoxyphenyl-Methidathion insecticidal activity, 6, 576 as insecticide, 1, 196 Methine, dipteridyl-synthesis, 3, 303 Methine dyes, 1, 323-325, 332 L-Methionine, S-adenosyl-in metabolic iV-methylation, 1, 236 Methionine, dehydro- C NMR, 6, 139 X-ray crystallography, 6, 136 Methiothepin... 

Epicillln Floxaclllin Methicillin sodium Nafcillin sodium Oxacillin sodium Penicillin V... 

Methicillin-resistent staphylococci are strains of staphylococci, which show resistance to a wide variety of antibiotics. They are named for their resistance to methicillin, a (3 -lactamase-resistant penicillin. Methicil-lin-resistante Staphylococcus aureus (MRSA) has become a serious problem particularly in hospitals. 

The antibiotics of choice for treating methicillin-sensitive S. aureus (MSSA) infections are penicillinase-stable penicillins and first-generation cephalosporins. 

It is important to determine (1) whether the isolate is methicillin-susceptible or methicillin-resistant and (2) whether the patient has a prosthetic valve. For patients with no prosthetic material, methicillin-susceptible staphylococci treatment should consist of a penicillinase-resistant penicillin (e.g., nafcillin or oxacillin) with or without gentamicin, and for methicillin-resistant strains, therapy should consist of vancomycin (see Table 71-4). Combination therapy with aminoglycosides, when used in these patients, typically is given only during the first 3 to 5 days of therapy. In the absence of prosthetic material, some treatment guidelines do not recommend combination therapy against MRSA. However, many clinicians may combine either gentamicin or rifampin with vancomycin if the patient is unresponsive to monotherapy. 

Streptococcus pneumoniae Penicillin susceptible Penicillin intermediate Penicillin resistant Group B Streptococcus Staphylococcus aureus Methicillin susceptible Methicillin resistant Staphylococcus epidermidis Listeria monocytogenes... 

In penicillin-allergic patients, oral or parenteral clindamycin may be used. Alternatively, a first-generation cephalosporin such as cefazolin (1 to 2 g IV every 6 to 8 hours) may be used cautiously for patients who have not experienced immediate or anaphylactic penicillin reactions and are penicillin skin test negative. In severe cases in which cephalosporins cannot be used because of documented methicillin resistance or severe allergic reactions to /1-lactam antibiotics, IV vancomycin should be administered. 

Joint replacement S. aureus, S. epidermidis Cefazolin 1 gx 1 preoperatively, then every 8 hours x 2 more doses Vancomycin reserved for penicillin-allergic patients or where institutional prevalence of methicillin-resistant Staphylococcus aureus warrants use IA... 

The emergence of multidrug-resistant Gram-positive bacteria, such as methicillin-resistant Staphylococcus aureus (MRSA), penicillin-resistant Streptococcus pneumoniae (PRSP), and vancomycin-resistant enterococci... 

The bacterium Staphylococcus aureus, which is a major cause of infection in the developed countries, is now resistant to most antibiotics. It is usually present on the skin, where it causes no problems, but it can invade the body through cuts and wounds, including those caused by surgery. These bacteria are now prevalent in many hospitals, so that infection is a major problem for the medical staff in hospitals. The resistant bacterium is known as methicillin-resistant Staphylococcus aureus (MRSA). It is also known in the mass media as the super bug . Penicillin kiUs bacteria because the P-lactam group in the antibiotic inhibits a reaction that is essential for bacterial ceU wall production. Consequently, the bacteria cannot proliferate. Resistance to penicillin in many bacteria is due to production of an enzyme, p-lactamase, that degrades P-lactams. The antibiotic methicillin is one of a group of semisynthetic penicillins in which the P-lactam group is not... 

An additional disadvantage with many penicillin and cephalosporin antibiotics is that bacteria have developed resistance to the drugs by producing enzymes capable of hydrolysing the P-lactam ring these enzymes are called P-lactamases. This type of resistance still poses serious problems. Indeed, methicillin is no longer used, and antibiotic-resistant strains of the most common infective bacterium Staphylococcus aureus are commonly referred to as MRSA (methicillin-resistant Staphylococcus aureus). The action of P-lactamase enzymes resembles simple base hydrolysis of an amide. 

Incompatibilities Do not mix IV minocycline before or during administration with any solutions containing the following Adrenocorticotropic hormone (ACTH), aminophylline, amobarbital sodium, amphotericin B, bicarbonate infusion mixtures, calcium gluconate or chloride, carbenicillin, cephalothin sodium, cefazolin sodium, chloramphenicol succinate, colistin sulfate, heparin sodium, hydrocortisone sodium succinate, iodine sodium, methicillin sodium, novobiocin, penicillin, pentobarbital, phenytoin sodium, polymyxin, prochlorperazine, sodium ascorbate, sulfadiazine, sulfisoxazole, thiopental sodium, vitamin K (sodium bisulfate or sodium salt), whole blood. 

Severe staphylococcal Infections - Severe staphylococcal infections (including methicillin-resistant staphylococci) in patients who cannot receive or who have failed to respond to penicillins and cephalosporins, or who have infections with resistant staphylococci. Infections may include endocarditis, bone infections, lower respiratory tract infections, septicemia, and skin and skin structure infections. 

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