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Antibiotic Medications |   |
| Penicillins, one of the oldest classes (dating back to the early 1940s), are considered the most important of the beta-lactam antibiotics. These bactericidal antibiotics are used for pneumococcal pneumonias, nonhospital-acquired aspiration pneumonia, and lung abscesses. |  |
The penicillin group is divided into three subgroups: the natural penicillins like penicillin G, penicillinase-resistant agents like methicillin, and the broad-spectrum penicilins like ampicillin.
Penicillin G is the agent of choice for streptococcus pneumomae, streptococcus pyogenes, and nonpenicillinase-producing staphylococcus aureus. Intramuscular or intravenous delivery is the preferred route of administration for acute and serious pulmonary infections.
Bacterial resistance to penicillin is caused by the production of the enzyme penicillinase, so a subgroup of the penicillins was created that are resistant to penicillinase, including: methicilin, nafcillin, oxacillin, and cloxacillin, which are effective against penicillinase-producing S-aureus.
Semisynthetic broad-spectrum penicillin derivatives used to treat gram-negative microorganisms include: ampicillin, amoxicillin, carbenicillin, piperacillin, and ticarcillin.
Ampicillin, available in several trade names (including Omnipen, Principen, Ampicin) is indicated treating systemic infections, acute and chronic urinary tract infections, and meningitis. It is used for pneumococcal pneumonia, bronchitis, bacterial exacerbations of COPD, streptococcus pneumoniae, and hemophilus influenzae.
Amoxicillin, an extended-spectrum penicillin, is indicated for lower respiratory infections. It is used for the same and is closely related to ampicillin. Both may be given orally but amoxicillin achieves an effective plasma concentration lasting twice as long as ampicillin. Recommended dosage for adults and children weighing more than 20 kg is PO 250-500 mg Q 8 hours.
Carbenicillin is effective against pseudomonas and other gram-negative bacteria, but not as effective as ampicillin against gram-positive organisms. It is generally used with another antibiotic to prevent development of resistant strains, and dosage may be administered in aerosol form in a 1-3 gram dose. Side effects frequently seen with the penicillins consist mainly of hypersensitivity reactions, and rashes, fever, and anaphylactic shock can occur. Cerebral irritation and gastrointestinal upset can be seen with higher doses.
Cephalosporins are a group of antibiotics originally derived from a fungus in the late 1940s. Like penicillin, they act by inhibition of bacterial cell synthesis, but they are resistant to penicillinase. Cephalosporins are active against both gram-negative and gram-positive bacteria, and are effective against staphylococcal, streptococcal, and kiebsiella pneumonias, along with proteus mirabilis and escherichia coli. Their primary use in pulmonary disease is concurrent with gentamicin for undiagnosed sepsis and for cephalosporin-sensitive gram negative organisms.
Carbapenems are members of the beta-lactam group of antibiotics that act by inhibition of bacterial cell wall syntheses, and have a wide spectrum of activity against both gram-positive and gram-negative organisms.
Monobactam (Azactam) is a synthetic bactericidal that is effective against a wide range of gram-negative aerobic organisms.