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Chapter 38 Antibiotics

Terms in this set (59)

Tetracycline
Natural and semisynthetic
Obtained from cultures of Streptomyces
Bacteriostatic - inhibit bacterial growth
Inhibit protein synthesis
Stop many essential functions of the bacteria.
Higher doses = bactericidal
Demeclocycline (Declomycin), Oxytetracycline (Terramycin), Tetracycline, Doxycycline (Doryx, Vibramycin), Minocycline (Minocin), Tigecycline (Tygacil)
Tetracycline: Indications
Wide spectrum: gram-negative and gram-positive organisms, protozoa, Mycoplasma, Rickettsia, Chlamydia, syphilis, Lyme disease, acne, others.
Demeoclocycline is also used to treat SIADH by inhibiting the action of ADH. Malaria prophylaxis.
Tetracycline: Adverse Effects
Strong affinity for calcium: discoloration of permanent teeth and tooth enamel in fetuses and children, or nursing infants if taken by the mother, may retard fetal skeletal development if taken during pregnancy.
Alteration in intestinal flora may result in: Superinfection (overgrowth of nonsusceptible organisms such as Candida), Diarrhea, and Pseudomembranous colitis. (Add probiotic)
May also cause: Vaginal candidiasis, Gastric upset, Enterocolitis, Maculopapular rash, and other effects. Most significant, especially with Doxycycline, is photosensitivity.
Tetracycline: Contraindications
Bind to Ca+, Mg+, and Al+ to form insoluble complexes.
Patients under 8 yrs. old don't get; will turn teeth brown.
Don't administer with milk, antacids, or iron salts; will reduce oral absorption.
Some products contain alcohol or bisulfites; avoid in patients with known hypersensitivities or intolerances.
Tetracycline: Lab
Monitor renal and hepatic function and CBC periodically during long-term therapy.
May cause increased AST, ALT, serum alkaline phosphatase, bilirubin, and amylase concentrations.
Except doxycycline, it may cause increased serum BUN.
Tetracycline: Patient Education
Finish medication. Take missed dose ASAP. Don't double dose. Don't share medication. Avoid taking milk or other dairy products. Avoid taking antacids, zinc, calcium, magnesium- or aluminum-containing meds, sodium bicarbonate, and iron supplements within 1-3 hr or oral tetracycline. Notify doc if rash, diarrhea, abdominal cramping, fever, or bloody stool occur. Use additional contraceptive. Minocycline commonly causes dizziness or unsteadiness. Avoid driving or activities that require alertness. Use sunscreen or protective clothing. Report signs of superinfection. Notify doc if taking any supplements or OTC meds. Notify doc of med regimen before treatment or surgery. Notify doc if symptoms don't improve. Discard outdated or decomposed meds. Malaria Prophylaxis: avoid being bitten by mosquitoes by using protective equipment. Doxycycline taken before, during, and after visiting malarious area; not exceeding 4 months.
What is a community-acquired infection?
Infection acquired outside of the hospital.
What is a health-care associated infection?
An infection acquired while in the hospital or health-care setting. Not present during admission. More difficult to treat and more virulent. 10% of hospitalized patients. MRSA most common. Nosocomial is other name.
How do you prevent health care associated infections?
Handwashing is #1
Disinfectant
Antiseptic
What is a disinfectant?
Kills organisms.
Used only on nonliving objects.
What is an antiseptic?
Inhibits growth of microorganisms but doesn't kill them.
Living tissue only.
What are antibiotics?
Medications used to treat bacterial infections.
Culture before antibiotic therapy. Identifies specific microorganism and reduces antibiotic resistance. Empirical treatment until results come back.
Why is gram negative bacteria harder to kill?
Cell wall is thicker.
Harder for antibiotic to penetrate membrane.
Longer to be effective.
What are the 6 sites of antibiotic activity?
Cell wall synthesis: Beta-lactams, Vancomycin, Polymyxin.
DNA replication: Metronidazole, Quinolones.
RNA synthesis: Rifampin, Rifabutin
Antimetabolites: Sulfonamides, Trimethoprim.
Protein synthesis (30S ribosomes): Tetracyclines.
Protein synthesis (50S ribosomes): Macrolides, Clindamycin.
What is empiric therapy?
Treatment of an infection before specific culture information has been reported or obtained.
What is definitive therapy?
Antibiotic therapy tailored to treat organism identified with cultures.
Doxycycline treats spirochetes.
Ciprofloxacin is good for pseudomonas.
What is prophylactic therapy?
Treatment with antibiotics to prevent an infection, as in intraabdominal surgery or after trauma.
What is a therapeutic response?
Decrease in specific signs or symptoms of infection are noted (fever, elevated WBC, redness, inflammation, drainage, pain). Normal WBC = 5-10,000 Normal Albumin = 3.5-5.5.
What is a subtherapeutic response?
Signs and symptoms of infection do not improve.
Serum albumin is low.
Consider route that alters effectiveness.
What are some negative things that can occur while taking antibiotics?
Superinfection: from antibiotic use; yeast, thrush, fungal. Can't cure = superbug.
Pseudomembranous colitis = Clostridium difficile (one med to treat); killing off good bacteria.
Resistance: some strains of TB.
Secondary infection
Food-drug interactions: Tetracycline and milk inhibits absorption.
Host factors: a lot of comorbid conditions?
Allergic reactions: anaphylaxis to penicillin.
What does bactericidal mean?
Kill bacteria
What does bacteriostatic mean?
Inhibit growth of susceptible bacteria, rather than killing them immediately; will eventually lead to bacterial death.
Sulfonamides
First group of antibiotics.
Combined with another antibiotic due to drug resistance issues. (Ex: sulfamethoxazole combined with trimethoprim (SMZ-TMP) also known as Bactrim, Septra, or co-trimoxazole.)
Sulfonamides: Mechanism of Action
Bacteriostatic action
Prevent synthesis of folic acid required for synthesis of purines and nucleic acid.
Don't affect human cells or certain bacteria - they can use performed folic acid.
Only affect organisms that synthesize their own folic acid.
Sulfonamides: Indications
Effective against both gram-positive and gram-negative bacteria.
Treatment of UTIs caused by susceptible strains of: Enterobacter spp., E. coli, Klebsiella spp., etc.
Sinuses and MRSA.
Pneumocystis jirovecii pneumonia (PJP) - AIDS pneumonia.
Upper respiratory tract infections.
SMZ-TMP for outpatient Staph infection.
Used for patients allergic to penicillin.
Sulfonamides: Adverse Effects
Most common is photosensitivity.
Stevens-Johnson syndrome: bruises on face leading to necrosis.
Delayed cutaneous reactions; fever followed by a rash.
Sulfa allergy.
Crystalluria and Hepatotoxicity.
Penicillin
Bactericidal antibiotics.
Broad spectrum for both gram positive and negative bacteria.
Usually combined with beta-lactamase inhibitor to prevent beta-lactam ring in penicillin from being destroyed by the bacteria.
Inhibitors include clavulanic acid, tazobactam, and sulbactam.
Resistant drugs used last case scenario.
Natural penicillin
Penicillin G is injectable form. Penicillin V is PO form.
Amniopenicillin
Most commonly used. Gram positive organisms. Biggest complaint is diarrhea.
Amoxicillin and Ampicillin.
Extended-spectrum drugs
Only used in hospital for severe infections. Given IV.
Bactericidal. Low protein = less therapeutic effect.
Penicillin: Mechanism of Action
Enter the bacteria via the cell wall
Inside the cell they bind to penicillin-binding protein.
Once bound, normal cell wall synthesis is disrupted.
Result: bacteria cell lysis.
Do not kill other cells in the body.
Penicillin: Indications
Prevention and treatment of infections caused by susceptible bacteria, such as: Gram positive bacteria, including Strep, Enterococcus, and Staph.
Penicillin: Adverse Effects
Allergic reactions are common; including urticarial, pruritis, and angioedema. Increased risk of allergy to other beta-lactam antibiotics. If there is a reaction, we will never give it again. Won't receive cephalosporins either.
Common: Nausea, vomiting, diarrhea, and abdominal pain.
C. diff can occur.
Recommended to use probiotics.
Penicillin: Interactions
NSAIDs (compete for protein binding sites), Oral contraceptives, Warfarin (decrease vitamin K in gut which is a clotting factor; patient may hemorrhage), others.
A patient is receiving Augmentin (amoxicillin and clavulanic acid) liquid solution through a PEG tube. What is the purpose of the clavulanic acid?
It inhibits the action of the enzymes produced by beta-lactamase-producing bacteria.
Cephalosporins
Five generations based on antimicrobial activity.
Semisynthetic antibiotics
Structurally and pharmacologically related to penicillins.
Bactericidal action.
Broad spectrum.
Cephalosporins: First Generation
Good gram positive coverage.
Poor gram negative coverage.
Parenteral and PO forms.
Examples: Cefadroxil (Duricef, Ultracef), Cephradine (Velosef), Cefazolin (Ancef)-IV or IM, Cephalexin (Keflex)-PO.
Used for surgical prophylaxis, and for susceptible staph infections.
E. coli and Klebsiella.
Respiratory (#3) and urinary infections.
Excellent for bone, joint, and skin infections.
Cephalosporins: Second Generation
Good gram-positive coverage
Better gram-negative coverage than first generation.
Examples: Cefaclor (Ceclor) - government has stockpiled incase of biological terrorism, Cefprozil (Cefzil), Cefoxitin (Mefoxin) - IV and IM; prophylactically for abdominal or colorectal surgeries; also kill anaerobes; meningitis, Cefuroxime (Zinacef) - parenteral form; Ceftin is PO; surgical prophylaxis; doesn't kill anaerobes, Cefotetan (Cefotan).
Cephalosporins: Third Generation
Most potent group against gram-negative bacteria.
Less active against gram-positive bacteria.
Examples: Cefotaxime (Claforan), Ceftazidime (Fortaz), Cefdinir (Omnicef), Ceftizoxime (Cefizox), Ceftriaxone (Rocephin)
Ceftriaxone (Rocephin)
Third generation Cephalosporin
IV and IM, long half-life, once-a-day dosing
Elimination is primarily hepatic.
Easily passes meninges and diffused into CSF to treat CNS infections.
Ceftazidime (Ceptaz, Fortaz, Tazidime)
Third generation Cephalosporin
IV and IM forms
Excellent gram-negative coverage
Used for difficult-to-treat organisms such as Pseudomonas spp.
Excellent spectrum of coverage.
Resistance is limiting usefulness.
Cephalosporins: Fourth Generation
Broader spectrum of antibacterial activity than third generation, especially against gram-positive bacteria.
Staph and Strep infections.
Cephalosporins: Fifth Generation
Ceftaroline (Teflaro): broader spectrum of antibacterial activity, effective against a wide variety of organisms including MRSA.
Cephalosporins: Adverse Effects
Similar to penicillins: mild diarrhea, abdominal cramps, rash, pruritus, redness, edema.
Potential cross-sensitivity with penicillins if allergies exist.
Well tolerated unless IV or high dosages.
Superinfections occur if on it too long.
Concerned with kidneys (BUN, evaluate kidney function, 5-20, higher the number = more likely to have renal disease)
Creatinine should be 0.6-1.2
Some ill patients in hospital have a slightly elevated BUN anyways.
Carbapenems
Broadest antibacterial action of any antibiotics to date.
Reserved for complicated body cavity and connective tissue infections in acutely ill hospitalized patients.
May cause drug-induced seizure activity
Risk can be reduced with proper dosage.
Imipenem/cilastatin (Primaxin): treatment of bone, joint, skin, and soft-tissue infections; many other uses; highly potent -used with severely ill patients; Cilastatin inhibits an enzyme that breaks down imipenem.
Other examples: meropenem (Merrem), ertapenem (Invanz), doripenem (Doribax).
Monobactams
Aztreonam (Azactam): synthetic beta-lactam antibiotic, primarily active against aerobic gram-negative bacteria (E. coli, Klebsiella spp., Pseudomonas spp.), bactericidal, parenteral use only, used for moderately severe systemic infections and UTIs.
Used when first or second line drugs aren't working.
Macrolides
Include erythromycin (E-mycin, E.E.S, others) - first drug for rheumatic fever, azithromycin (Zithromax), and clarithromycin (Biaxin).
Macrolides: Mechanism of Action
Prevent protein synthesis within bacterial cells.
Considered bacteriostatic.
Bacteria will eventually die.
In high enough concentrations, may also be bactericidal.
Patient won't feel better initially, because it takes time.
Macrolides: Indications
Strep infections (second choice for): Streptococcus pyogenes.
Mild to moderate URI and LRI: Haemophilus influenza
Spirochetal infections: syphilis and Lyme disease.
Gonorrhea, Chlamydia, and Mycoplasma.
Azith. and Clari. approved for Mycobacterium avium-intracellulare complex infection (opportunistic infection associated with HIV/AIDS).
Clarithromycin recently approved for use in combination with omeprazole for treatment of active ulcer disease associated with Helicobacter pylori infection. (Advise patient to have 30 mls pepto 3 times a day to coat stomach and relieve the burning).
Macrolides: Adverse Effects
GI effects, primarily with erythromycin: Nausea, vomiting, diarrhea, hepatotoxicity, flatulence, jaundice, anorexia.
Azith. and Clari.: fewer GI adverse effects, longer duration of action, better efficacy, better tissue penetration.
Hepatotoxicity is rare. Anorexia comes because of abdominal discomfort.
Careful when combining with Warfarin, antihistamines, and antifungals.
Before beginning antibiotic therapy, what should you do?
Assess drug allergies and lab studies (renal, liver, and cardiac function).
Get thorough patient history including immune status. Are they currently sick with something else?
Assess for conditions that may be contraindicative or indicate cautious use.
Assess for potential drug interactions.
OBTAIN CULTURE BEFORE GIVING ANTIBIOTICS.
Check medication name carefully (Sound alike, look alike drugs)
What should you instruct the patient to do while taking an antibiotic?
Finish the medication and take it as prescribed.
Assess for signs and symptoms of Superinfection: fever, perineal itching, cough, lethargy, or any unusual discharge.
Take with at least 6-8 oz of water to help with absorption.
Monitor for adverse effects including: diarrhea, nausea, vomiting or drug interactions.
Monitor for therapeutic effects: improvement of signs and symptoms of infection, return to normal vital signs, negative culture and sensitivity tests, and disappearance of fever, lethargy, drainage, and redness.
When completing an admission assessment, the patient states that she is allergic to sulfa drugs. What will the nurse do next?
Ask the patient for more information about the allergic reaction she had.
A patient has a prescription for a sulfa drug as treatment for a urinary tract infection. She is also taking an oral contraceptive, an oral sulfonylurea antidiabetic drug, and phenytoin for a history of seizures. Which drug may pose a potential serious interaction with the sulfa drug?
All of these (oral contraceptive, oral antidiabetic drug, and phenytoin).
What should be done when taking Sulfonamides?
Take with 2000 to 3000 mL of fluid every 24 hours.
Assess RBCs prior to beginning therapy.
Take oral doses with food.
What should be done when taking Penicillins?
Take oral doses with water (not juices) as acidic fluids may nullify drug's antibacterial action.
Monitor patients taking penicillin for an allergic reaction for at least 30 minutes after administration.
What should be done when taking Cephalosporins?
Assess for penicillin allergy; may have cross allergy.
Give orally administered forms with food to decrease GI upset, even though this will delay absorption.
What should be done when taking Macrolides?
These drugs are highly protein-bound and will cause severe interactions with other protein-bound drugs.
The absorption of oral erythromycin is enhanced when taken on an empty stomach, but because of the high incidence of GI upset (stabbing pain), many drugs are taken after a meal or snack.
What should be done when taking Tetracyclines?
Avoid milk products, iron preparations, antacids, and other dairy products because of the chelation and drug-binding that occurs.
Take all meds with 6-8 oz of fluid, preferably water.
Because of photosensitivity, avoid sunlight and tanning beds.
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