Drugs Used to Treat Infections

1. Drugs Used to Treat Infections Chapter 5

2. Antimicrobials • Drugs used to prevent or treat infection caused by pathogens

3. Two Classifications • Bactericidal drugs kill bacteria directly • Bacteriostatic drugs prevent bacteria from dividing

4. Infectious Disease • Infections disease involves the presence of pathogen plus clinical signs and symptoms indicating infection. • Microorganisms spread by direct contact with infected person or contaminated hands, food, water, or objects.

5. Common Bacterial Pathogens • Gram positive • Staphylococcus aureus • Streptocci • Enterococci • Gram negative • Escherichia coli or E-coli • Klebsiella • Proteus • Pseudomonas

6. Streptococci • Part of the normal microbial flora of throat and nasopharynx • Common cause of pneumonia, otitis media (ear infection), sinusitis, and meningitis • Pneumococcal vaccination available for children / adults • Often follows a viral illness that injures the ciliated epithelium of respiratory tract

7. Opportunistic Infections • Severe burns • Cancer • HIV • Indwelling IV catheter or urinary catheter • Corticosteroid therapy • Fungal or viral infections

8. Laboratory Tests • Gram stain – microscopic identification of organism • Culture – identifies causative agent and susceptibility to specific antibiotics • Serology – titers or antibodies measured • CBC – looking at WBC

9. Cultures • Throat • Wound • Urine • Sputum • Blood

10. Clinical Pearl • Always collect culture: urine, sputum, wound drainage, or blood prior to starting antibiotic therapy. • If technician is drawing blood make sure it has been done before starting antibiotics.

11. Two Types of Bacteria • Aerobic – grow and live in presence of oxygen • Staph & Strep • Anaerobic – cannot grow in presence of oxygen • Deep wounds • Characterized by abscess formation, foul-smelling pus and tissue destruction

12. Community-Acquired Infection • Less severe and easier to treat, although drug resistant strains are increasing • Remember Staph is everywhere – it is normal flora on skin and in the upper respiratory tract • MRSA: methicillin-resistant-Staphylococcus aureus

13. Nosocomial Infections • More severe and difficult to manage because they often result from drug-resistant microorganisms and occur in clients whose resistance is impaired • Pseudomonas • Proteus

14. Bacterial Resistance • Bacteria develop the ability to produce substances which block the action of antibiotics or change their target or ability to penetrate the cells.

15. What causes resistance? • Widespread use of antimicrobial drug • Interrupted or inadequate antimicrobial treatment of infection • Type of bacteria – gram-negative strains have higher rates of resistance • Re-occurring infections • Condition of the host • Location – critical care areas

16. Host Defense Mechanisms • Skin • Mucous membranes • Secretions in GI, GU and respiratory tract • Coughing, swallowing, peristalsis • WBC – phagocytes – battling white cells • Elevated in the presence of infection

17. Break-down of Natural Barriers • Breaks in skin, open lesions, prosthetic devices (total hip or knee) • Urinary catheters • Intravenous catheters • Impaired blood supply • Malnutrition • Poor personal and oral hygiene • Neonate / Geriatric

18. Client History / Assessment • Allergies • Previous drug reactions • Baseline renal and liver function • Review culture reports for appropriate antibacterial drug choice • Patient response to antibiotics therapy • Are they getting better? • Any side effects?

19. Drug Selection • Empiric therapy – antibiotics may need to be started before the organism is identified • Cultures take 48 to 72 hours • A single broad spectrum may be used to cover suspected organism

20. Switching Antibiotics • If cultures indicate a specific antibiotic • If the infection is not getting better

21. Cost • Designer drugs are more expensive • Generic brands may work just as well

22. Beta-Lactam Antibacterials Chapter 30

23. Penicillin • First generation IM or IV • Newer penicillins have been developed that increase gastric acid stability of penicillin • Good drug since it enters most bodily fluids: joint, pleural, and pericardial. • Not effective against intraocular (eye) or cerebral spinal fluid infection (CNS)

24. Penicillin • Bactericidal action against sensitive bacteria • Action: binds to bacterial wall, resulting in cell death

25. Nursing Implications • Vital signs • Review lab values especially culture results • Ask about previous drug reactions or allergies • Observe for allergic reaction • IM or IV may occur within 20 to 30 minutes after administration • PO may occur in a few days

26. Client Teaching • Take around the clock as ordered • Observe for super-infections: vaginal discharge, diarrhea, rash or allergic reaction • Call MD is fever persists after 24 to 36 hours.

27. Ampicillin – Synthetic Penicillin • Broad spectrum effective against several gram-positive and gram-negative bacteria • E-coli, proteus, Salmonella, Shigella • Not effective against staphylococci on gonococci • Bronchitis, sinusitis, and otitis media

28. Ampicillin • Bactericidal action – spectrum is broader than penicillin • Binds to bacterial wall resulting in cell death

29. Nursing Implications • Same as penicillin • Ask client about oral contraceptive use – drug may cause transient decrease in effectiveness • Advise to use additional BC – barrier protection during antibiotic therapy

30. Amoxicillin • Oral equivalent of Ampicillin • Readily absorbed and reaches therapeutic levels rapidly • Drug of choice in prevention of bacterial endocarditis • Clients with total knee or hip replacement, heart valve replacement need to take prior to any dental work, endoscopy exams

31. Amoxicillin • Action: binds to bacterial cell wall causing cell death. • Therapeutic effects: bactericidal action • Spectrum is broader than penicillin • Well absorbed from duodenum • More resistant to acid inactivation than other penicillins

32. Nursing implication / client teaching • Same as penicillin • Instruct female clients taking oral contraceptives to use an alternate or additional non-hormonal method of contraception during antibiotic therapy

33. Dosing for Amoxicillin • Adults: 250 to 500 mg q8h • Infants and children less than 20 kg: • 20 – 40 mg / kg / day divided into doses q 8 hours

34. Cephalosporins • Widely used drug derived from fungus • Used against gram–negative bacteria • Widely absorbed and distributed in most bodily fluids – placenta and breast milk • First generation Cephalosporin drugs do not reach therapeutic levels in CNS but 2nd, and 3rd generation drugs do – especially important in treating meningitis

35. First Generation Cephalosporins • Not used very much since better drugs have been developed • Bactericidal action – binds to bacterial cell wall, causing cell death • Keflex (PO) still used extensively in treatment of skin infections • Ancef – often ordered preoperatively

36. Keflex • First generation cephalosporin • Action: binds to bacterial cell wall membrane, causing cell death • Therapeutic effect: bactericidal action against susceptible bacteria • Active against many gram-positive cocci – step and staph

37. Client teaching • May be taken with or without food but food may minimize the GI irritation • Distribution: may cross placenta or enter breast milk in low concentrations. • Excreted entirely by the kidneys.

38. Keflex Dosing • Adults: 250 – 500 mg q 6 hours • Children: 25 – 50 mg / kg / day in divided doses q 6 h

39. Cefazolin or Ancef • Cefazolin – first generation cephalosporin • Well absorbed following IM or IV administration • Crosses to placenta and breast milk in small concentrations • Minimal CSF penetration • Excreted by kidneys

40. Ancef Dosing • IV • Used for UTI, bone and skin infections, endocarditis • Not suitable for treatment of meningitis • Perioperative prophylaxis – 1 gram within 60 minutes of incision and than every 8 hours for 24 hours

41. Second-Generation Cephalosporins • More active against some gram-negative organisms and anaerobic organisms than the first generation drugs. • May be effective in infections resistant to other antibiotics • Penetration into CSF is poor but adequate to be used in meningitis • Action: bactericidal – binds to cell wall

42. Ceclor • PO Cephalosporin: • Adult: 250 – 500 mg q 8 h • Children: 20 - 40 mg/kg/d in 3 divided doses

43. Practice Problem • 22 pound child • Minimal dose of 20 mg per kg • Given q 8 hours • 22 pounds to kilogram = 10 kg • 20 mg x 10 kg = 200 mg po q day • 200 divided by 3 = 66 mg / dose

44. Cefuroxime • UTI (urinary tract infection), otitis media (ear infection), pharyngitis (throat infection) or URI (upper respiratory infection) • Meningitis

45. Cefuroxime • PO • Adults – 250 to 500 mg every 12 hours • Children – 15 mg / kg / q 12 hours • IM or IV • Adults – 1.5 grams every 12 hours • Children – • 16.7 – 33.3 mg / kg / q 8 hours • 15 – 50 mg / kg / q 12 hours

46. Second – Generation Cephalosporin • Cefuroxime: penetrates cerebrospinal fluid in presence of inflamed meninges • Bacterial meningitis: 200 to 240 mg / kg / d in divided doses reduced to 100 mg / kg / dose • Moderate infections: • > 3 months 50 to 100 mg / kg / d in 3 divided doses

47. Third – Generation Cephalosporins • Extended protection against gram-negative organisms • Used against some resistant organisms to the first and second generation Cephalosporins • Increased activity against – Enterobacter, Haemophilus influenza, E. Coli

48. Cephalosporins • Third – Generation: Claforan – serious infections resistant organisms – E. Coli, Proteus, Klebsiella • Fourth – Generation: only used if organism resistant

49. Aminoglycosides and Fluoroquinolones Chapter 31

50. Aminoglycosides • Bactericidal action – inhibits protein synthesis at level of 302 ribosome • Treatment of serious gram-negative bacilli and infections caused by staphylococci when penicillin or less toxic drugs are contraindicated