Antimicrobial Drugs & Antibiotics

• Selecting an appropriate antimicrobial drug involves isolating and identifying the microorganism, determining its susceptibility to drugs, considering the infection site, drug cost, potential adverse effects, and patient allergies.
• Treatment usually starts at assessment, then is re-evaluated when test results are obtained in 48 hours.
• Pathogen resistance is a limitation, where microorganisms can live and grow despite the presence of antimicrobial drugs.
• Resistance usually results from genetic mutation, which may lead to the microorganism's ability to resist bacteriostatic or bactericidal actions.

Antibacterial Drugs

• Antibacterial drugs (antibiotics) treat systemic bacterial infections.
• Classifications include Aminoglycosides, Penicillins, Cephalosporins, Tetracyclines, Lincomycin Derivatives, Macrolides, Vancomycin, Carbapenems, Monobactams, Fluoroquinolones, Sulfonamides, and Nitrofurantoin.

Aminoglycosides

• Aminoglycosides are effective against Gram-Negative Bacilli, some Aerobic Gram-Positive Bacteria, Mycobacteria, and some Protozoa.
• Common aminoglycosides include Amikacin Sulfate, Gentamicin Sulfate, Kanamycin Sulfate, Neomycin Sulfate, Paromomycin Sulfate, Streptomycin Sulfate, and Tobramycin Sulfate.
• Aminoglycosides are poorly absorbed from the GI tract, so parenteral administration is typical.
• After I.V. or I.M. administration, absorption is rapid and complete.
• Aminoglycosides are distributed widely in extracellular fluid, cross the placental barrier, but do not cross the blood-brain barrier.
• Aminoglycosides aren't metabolized and are excreted primarily unchanged by the kidneys.
• Aminoglycosides are bactericidal drugs and act by binding to the bacterium’s 30S subunit, thereby interrupting protein synthesis.
• Penicillin and aminoglycoside therapy combined alter the cell wall, allowing the aminoglycoside to penetrate the bacterial cell and treat gram-positive organisms such as staphylococcal or enterococcal infections, increasing the drugs’ effectiveness.
• Aminoglycosides treat infections caused by gram-negative bacilli, serious nosocomial infections, Urinary Tract Infections, and infections of the Central Nervous System (CNS) and the eye.
• They are inactive against anaerobic bacteria.
• Streptomycin is active against many strains of mycobacteria, including Mycobacterium tuberculosis, and against the gram-posi-tive bacteria Nocardia and Erysipelothrix.
• Amikacin, gentamicin, and tobramycin are active against Acine-tobacter, Citrobacter, Enterobacter, Klebsiella, Proteus, Providencia, Serratia, Escherichiacoli, and Pseudomonas aeruginosa.
• Carbenicillin and ticarcillin reduce the effects of aminoglycosides, especially when mixed in the same container or I.V. line.
• Combining aminoglycosides with neuromuscular blockers increases neuromuscular blockade, resulting in increased muscle relaxation and respiratory distress.
• The risk of renal toxicity increases when aminoglycosides are taken with cyclosporine, amphotericin B, or acyclovir.
• Antiemetic drugs may mask ototoxicity symptoms.
• Loop diuretics taken with aminoglycosides increase the risk of ototoxicity.
• Hearing loss may be irreversible with aminoglycosides.

Aminoglycosides: Nursing Considerations

• Assess for allergies, renal or hepatic disease, preexisting hearing loss, active infection with herpes, vaccinia, varicella, fungal infections, mycobacterial infections, myasthenia gravis, parkinsonism, infant botulism, lactation, pregnancy.
• Assess site of infection, skin color/lesions, orientation/reflexes, eighth cranial nerve function, P/BP, R/adventitious sounds, bowel sounds/liver evaluation.
• Assess urinalysis, BUN, serum creatinine, serum electrolytes, LFTs, CBC.
• Give by IM route if possible; give by deep IM injection.
• Culture infected area before therapy.
• Use 2 mg/mL intrathecal preparation for intrathecal use without preservatives.
• Avoid long-term therapies due to increased risk of toxicities, a reduction in dose may be clinically indicated.
• Patients with edema or ascites may have lower peak concentrations.
• BLACK BOX WARNING: Monitor hearing and renal function with long-term therapy.
• Apply ophthalmic preparations by tilting head back, place medications into conjunctival sac, close eye, apply light pressure on lacrimal sac for 1 minute.
• Ensure area is cleansed before applying dermatologic preparations.
• Patients may experience ringing in the ears, headache, dizziness, nausea, vomiting, loss of appetite, burning, blurring of vision, photosensitization.
• Instruct patients to report pain at injection site, severe headache, dizziness, loss of hearing, changes in urine pattern, difficulty breathing, rash or skin lesions, itching or irritation, or worsening of the condition.

Penicillins

• Penicillins are divided into Natural Penicillins, Penicillinase-Resistant Penicillins, Aminopenicillins, and Extended-Spectrum Penicillins.
• Natural Penicillins include Penicillin G Benzathine, Penicillin G Potassium, Penicillin G Procaine, Penicillin G Sodium, and Penicillin V Potassium.
• Penicillinase-Resistant Penicillins include Dicloxacillin, Nafcillin, and Oxacillin.
• Aminopenicillins include Amoxicillin and Ampicillin.
• Extended-Spectrum Penicillins include Carbenicillin and Ticarcillin.
• After oral administration, Penicillins are absorbed mainly in the duodenum and the upper jejunum.
• Absorption of oral penicillin varies and depends on the particular penicillin used, pH of the patient’s stomach and intestine and presence of food in the GI tract.
• Most Penicillins should be given on an empty stomach unless it is amoxicillin, penicillin V, and amoxicillin/clavulanate potassium.
• Penicillins are distributed widely, and will appear in the lungs, liver, kidneys, muscle, bone, and placenta.
• High concentrations also appear in urine, making penicillins useful in treating UTIs.
• Penicillins are metabolized to a limited extent in the liver and are excreted 60% unchanged by the kidneys, the remaining amounts of Nafcillin and oxacillin are excreted in bile.
• Penicillins bind reversibly to penicillin-binding proteins (PBPs), which are involved in cell-wall synthesis and cell division, causing a rapid destruction of the cell.
• No other class of antibacterial drugs provides as wide a spectrum of antimicrobial activity as the penicillins as they cover gram-positive, gram-negative, and anaerobic organisms.
• Penicillin is given by an I.M. injection when oral administration is inconvenient due to long-acting preparations.
• Probenecid increases the plasma concentration of penicillins.
• Penicillins reduce tubular secretion of methotrexate in the kidney, increasing the risk of methotrexate toxicity.
• Tetracyclines and chloramphenicol reduce the bactericidal action of penicillins and Neomycin decreases the absorption of penicillin V.
• Penicillin V or ampicillin reduces the effectiveness of hormonal contraceptives, so alternative methods of contraception should be used during therapy.
• Large doses of I.V. penicillins can increase the bleeding risk of anticoagulants and Nafcillin and dicloxacillin have been implicated in warfarin resistance.
• High dosages of penicillin G and extended-spectrum penicillins inactivate aminoglycosides and penicillins shouldn’t be mixed in the same I.V. solutions with aminoglycosides.

Penicillins: Precautions

• Penicillins are contraindicated if an allergy is present or if a severe drug hypersensitivity reaction has happened in the past, including anaphylaxis, Stevens-Johnson syndrome (SJS), or toxic epidermal necrolysis (TEN).
• Common side effects include diarrhea, headache, stomach upset, nausea/vomiting, rash or hives, injection site pain, black hairy tongue, oral thrush, and vaginal yeast infection.

Penicillins: Nursing considerations

• Assess allergies to penicillins, cephalosporins, or other allergens; renal disorders; pregnancy; lactation.
• Assess the culture infection on the skin, R, bowel sounds and test CBC, LFTs, renal function, serum electrolytes, Hct, urinalysis.
• Culture infection and reculture if the response is not as expected.
• Continue therapy for at least 2 days after infection has disappeared, typically 7–10 days.
• Do not administer the oral drug with milk, fruit juices, or soft drinks, water is preferred.
• Avoid self-treating infections other than the one being treated and complete the full course of drug therapy.
• You may experience side effects of nausea, vomiting, diarrhea, or mouth sores.
• Report difficulty breathing, rashes, severe diarrhea, mouth sores, and unusual bleeding or bruising.