Beta-Lactams The beta-lactams include penicillins, cephalosporins, cephamycins, carbacephems, clavams, carbapenems, monobactams. The mode of action (MOA) of all beta-lactams is to bind to and inactivate enzymes required for bacterial wall synthesis. Penicillins. Penicillins specifically inhibit peptidoglycan cross-links in the bacterial cell wall. They are used for disease due to gram-positive organisms and some gram-negative cocci. Penicillin is the drug of choice for syphilis and endocarditis caused by susceptible enterococci. These medications are inexpensive but can cause a life-threatening anaphylactic reaction in those who are allergic. Penicillin G-like drugs : Disease due to gram-positive organisms and some gram-negative cocci Subtypes : Penicillin G Oral and parenteral Penicillin G benzathine Parenteral Penicillin G procaine (procaine, a local anesthetic, relieves injection pain) Parenteral Penicillin V Ampicillin-like drugs : Disease due to enterococci and certain gram-negative bacilli Subtypes : Ampicillin Parenteral Ampicillin plus sulbactam Parenteral Amoxicillin Oral Amoxicillin plus clavulanate Oral Penicillinase-resistant penicillins : Penicillinase-producing Staphylococcus aureus Subtypes : Dicloxacillin Oral Nafcillin Oral and parenteral Oxacillin Oral and parenteral Antipseudomonal penicillins : Similar to ampicillin but also active against some strains of Enterobacter and Serratia and many strains of Pseudomonas aeruginosa Subtypes: Piperacillin (and piperacillin/tazobactam) Intravenous Ticarcillin (and ticarcillin/clavulanate) Intravenous Cephalosporins. Cephalosporins are bactericidal with both gram-positive and gram-negative activity. They are grouped by generation. They do not produce the anaphylactic reactions that can occur with penicillins, but some patients are allergic to both penicillins and cephalosporins. These medications penetrate well into most body fluids, especially when inflammation is present. Cefaclor at usual doses and other members of the class at higher doses have been associated with serum sickness. Later generations are usually more active against aerobic gram-negative bacilli and therefore may have efficacy in disease due to these organisms. Some third-generation cephalosporins have relatively poor activity against gram-positive cocci. A fourth-generation cephalosporin, cefepime, is active against gram-positive cocci and gram-negative bacilli, including Pseudomonas aeruginosa;however, it has not been shown to be superior in efficacy to older drugs. These medications penetrate well into most body fluids, especially when inflammation is present. First generation : CefadroxilOral Cefazolin,Parenteral Cephalexin Oral Cephradine Oral Second generation : Cefoclor Oral Cefotetan Parenteral Cefoxitin Parenteral Cefprozil Oral Cefuroxime Oral and parenteral Loracarbef Oral Third generation : Cefdinir Oral Cefditoren Oral Cefixime Oral Cefoperazone Parenteral Ceftazidime Parenteral Ceftibuten Oral Ceftizoxime Parenteral Ceftriaxone Parenteral Fourth generation : CefepimeParenteral Other beta-lactams. Other beta-lactams include monobactams and carbapenems. Monobactam : May have less potential to cause allergic reactions in people allergic to other penicillin-like drugs. Subtypes : Aztreonam Parenteral Carbapenems : Patients who have rash but not immediate hypersensitivity to penicillin may be less likely to have allergic reactions Subtypes : Imipenem Parenteral Meropenem Parenteral Doripenem Parenteral Glycopeptides Examples of glycopeptides include vancomycin, which is administered by injection, and teicoplanin (not approved for use in the United States). MOA. The MOA for glycopeptides is to form complexes with bacterial cell wall peptides by binding at the free carboxyl end. Indications. Glycopeptides are used for patients with penicillin allergy or when bacteria that cause serious infections, such as methicillin-resistant Staphylococcus aureus (MRSA), are resistant to first-line drugs. Risk-benefit. These drugs may cause skin redness ("red man syndrome") when quickly administered intravenously. In such cases, the drug can still be given at a slower rate. Less common adverse events include decreased platelet count. Aminoglycosides Aminoglycosides include gentamicin, amikacin, netilmicin, and streptomycin, which can all be administered administered orally or parenterally. Tobramycin can be administered by inhalation.[5] MOA. Aminoglycosides act at the outer bacterial membrane, creating fissures that allow enhanced antibiotic uptake and leakage of intracellular contents. Indications. They are effective against aerobic, gram-negative bacteria and certain gram-positive organisms. These drugs can also be used for prophylaxis, especially against endocarditis. Aminoglycosides are commonly used to treat abdominal and urinary tract infections, and some agents are used as inhaled drugs to treat respiratory tract infections in patients with cystic fibrosis. Risk-benefit. There is a substantial risk for nephrotoxicity, especially when combined with other medications. Quinolones Quinolones include ciprofloxacin, norfloxacin, ofloxacin, and gemifloxacin, which are orally administered, and moxifloxacin and levofloxacin, which can be administered orally and parenterally. MOA. The quinolone class acts by inhibiting topoisomerases, enzymes necessary for bacterial DNA replication. Indications. Quinolones are indicated for community-acquired pneumonia, skin infections, prostatitis, and urinary tract infections. Of note, ciprofloxacin is used for postexposure prophylaxis of inhalation anthrax. Risk-benefit. Use of these drugs has been associated with blood glucose disturbances (especially in diabetic patients taking oral hypoglycemics), arrhythmias, tendon ruptures (especially in those taking corticosteroids), neuropathy, and central nervous system events, including nervousness, agitation, insomnia, anxiety, nightmares, or paranoia. Safer alternatives to these drugs exist. Sulfonamides Antibacterial sulfonamides were commonly called sulfa drugs. Sulfamethoxazole, the most common sulfonamide, is used in combinations, including erythromycin-sulfisoxazole and cotrimoxazole (trimethoprim-sulfamethoxazole). MOA. Antibacterial sulfonamides interfere with the production of folate through inhibition of enzyme production. They are bacteriostatic and stop bacterial growth, but they depend on the immune system to kill remaining organisms. Indications. Sulfonamides are used to treat enterocolitis, traveler's diarrhea, and bacterial urinary tract infections. They may also be used for prophylaxis and treatment of opportunistic infections in patients with AIDS, children born to HIV-infected mothers, and patients undergoing transplantation. Risk-benefit. Use of sulfonamides as single agents has decreased because of emergence of resistance. Rare but severe reactions include Stevens-Johnson syndrome, toxic epidermal necrolysis, hepatic necrosis, and blood dyscrasias. Sulfonamides are usually combined with other medications, most commonly trimethoprim. Combinations cause more adverse events than single agents do, and the benefits are unclear in certain infections, such as urinary tract infections. Complete blood counts should be done frequently in patients receiving the drug, especially when it is taken at high doses or for prolonged periods. Macrolides The macrolides include the oral agents azithromycin, erythromycin, and clarithromycin, the tetracyclines (tetracycline, doxycycline, tigecycline), the lincosamides (clindamycin, administered orally and parenterally), and the streptogramins (dalfopristin-quinupristin, administered parenterally) MOA. The macrolides bind to the ribosomes of susceptible microorganisms, resulting in inhibition of protein synthesis. Indications. Macrolides are used to treat pharyngitis, tonsillitis, community-acquired pneumonia, skin infections, and disseminated mycobacterial infections. Risk-benefit. The agents interact with certain antihistamines to cause cardiac arrhythmias and potentially death. They should not be used in pregnant women unless there is no appropriate alternative therapy. Some of these agents can be used once a day and for shorter courses of treatment Source
