Antibiotics

ANTIBIOTICS Antibiotics: • disrupts proteins or enzymes within a bacterium.  bacteriostatic – prevents multiplication  bactericidal – kills bacteria • Goal : to reduce the number of bacteria  immune system can deal with infection. Culture & Sensitivity test • identify the causative bacteria & the antibiotic which it is most sensitive  Gram- positive bacteria  cell wall retains stain or resist decolorization by alcohol  MC in respiratory & soft tissue infections  Gram – negative bacteria  cell wall loses stain or decolorized by alcohol  MC in GI & GU tract infections  Aerobic bacteria

vs

Anaerobic bacteria

 Broad – spectrum Antibiotic • used for both gram – positive & gram negative bacteria  Narrow – spectrum antibiotics • used for either gram – positive or gram – negative bacteria  Synergistic effect  combination of antibiotics produce greater effects ex. amoxicillin + clavulanic acid ( Augmentin) ampicillin + sulbactam (Unasyn)  Prophylaxis  prevention of potential infection. Antibiotic resistance: • bacteria mutate that they become resistant to certain antibiotics. • common in nosocomial infections • cause: indiscriminate antibiotic use Cross – resistance • resistance that occurs bw antibacterials with similar actions. General adverse reactions to antibacterials: 1. allergy / hypersensitivity reactions

2. superinfections 3. organ toxicity Classes of Antibiotics: I.

Aminoglycosides  gentamicin (Garamycin) • amikacin • • • •

II.

neomycin tobramycin streptomycin kanamycin

Cephalosporins  cefaclor (Ceclor) a. 1st generation • cephalexin (Keflex) • cefazolin (Zolicef)

IV.

V. Lincosamides  clindamycin • lincomycin VI. Monobactam Antibiotic  aztreonam VII. Penicillins & Penicillinase Resistant Antibiotics  Amoxicillin a. Penicillins • penicillin G • penicillin V

b. 2nd generation • cefaclor • cefuroxime ( Zinacef) • cefoxitin

b. extended- spectrum penicillin • amoxicillin • ampicillin

c. 3rd generation • ceftazidime • ceftriaxone (Rocephin) • ceftizoxime

c. penicillin – resistant antibiotics • dicloxacillin • nafcillin • oxacillin

d. 4th generation • cefepime • ceftditoren III.

• azithromycin (Zithromax) • clarithromycin

Fluoroquinolones  ciprofloxacin (Cipro) • levofloxacin • norfloxacin • ofloxacin • gatifloxacin Macrolides  erythromycin

VIII. Sulfonamides  sulfasalazine • sulfadiazine • cotrimoxazole IX. Tetracyclines  tetracycline • doxyclcine • minocycline X. Antituberculosis drugs XI. Leprostatic drugs

I. Aminoglycosides  gentamicin (Garamycin) • amikacin • neomycin • tobramycin • streptomycin • Kanamycin Indic: Tx of serious infections • Gm (-) infections {Kleb, enterobacter, E. coli. Proteus, Pseudomonas, Serratia- ( KEEPPS) } • Methicillin-resistant staph aureus (MRSA) Action: inhibits protein synthesis of gram (–) negative bacteria (bactericidal) Monitor for:     

nausea & anorexia ototoxicity nephrotoxicity neurotoxicity BM depression & superinfections

II. Cephalosporins  cefaclor (Ceclor) Indications: Tx of respiratory, dermatological, urinary tract & middle ear infections Actions: inhibits cell wall synthesis of wide-range of bacteria (bactericidal ) Monitor for:      

GI upsets & diarrhea Pseudomembranous colitis headache, dizziness nephrotoxicity superinfections & bone marrow suppression hypersensitivity reactions

b. 1st generation • cephalexin (Keflex) • cefazolin (Zolicef) Indications: same as gram – positive bacteria affected by Pen G & gram – negative bacteria ( Proteus mirabilis, E. coli, & Klebsiella pneumoniae) PEcK

c. 2nd generation • cefaclor • cefuroxime ( Zinacef) • cefoxitin Indications: same as above plus Haemophilus influenzae, Enterobacter aerogenes & Neisseria (HENPEcK) Less effective against gram – positive bacteria d. 3rd generation • ceftazidime • ceftriaxone (Rocephin) • ceftizoxime Indications: more potent against gram- negative bacilli as well as Serratia marcescens (HENPEcKS) e. 4th generation • cefepime • ceftditoren Indications: for gram – negative & gram – positive organisms including P. aeroginosa III.

Fluoroquinolones  ciprofloxacin (Cipro) • levofloxacin • norfloxacin • ofloxacin • gatifloxacin Indications: Tx of respiratory, skin, urinary tract, eye, ear, bone & joint infections. Tx after anthrax exposure, typhoid fever Action: inhibit synthesis of bacterial RNA & DNA in wide spectrum of gram – negative bacteria Monitor for:    

IV.

headache, dizziness GI upsets BM depression  CI in children < 18 yo risk of photosensitivity

Macrolides  erythromycin • azithromycin (Zithromax) • clarithromycin

Indications: Tx of respiratory, skin, urinary tract & GI infections Good alternative if allergic to penicillins Action: inhibit protein synthesis (bacteriostatic or bactericidal) Monitor for:   

nausea & vomiting, diarrhea, risk for pseudomonas colitis hepatotoxicity ototoxicty

V. Lincosamides  clindamycin • lincomycin Indications: similar to macrolides but more toxic. Tx of serious infections. Action: inhibit protein synthesis Monitor for:   

severe pseudomembranous colitis BM depression pain

VI. Monobactam Antibiotic  aztreonam Indications: Tx of lower respiratory, skin, urinary tract, intra-abdomina & gynecological infections caused by gram- negative bacteria including septicemia Alternative to pxs allergic to penicillins or cephalosporins. Action: inhibit cell wall synthesis of gram- negative enterobacteria Monitor for:    VII.

mild GI problems liver toxicity pain

Penicillins & Penicillinase Resistant Antibiotics  Amoxicillin a. Natural Penicillins • penicillin G • penicillin V b. extended- spectrum penicillin • amoxicillin • ampicillin

c. penicillinase – resistant antibiotics • cloxacillin • nafcillin • oxacillin Indications: Tx broad spectrum respiratory & urinary tract infections Action: inhibit cell wall synthesis (bactericidal) Monitor for:

VIII.

 GI effects  superinfections  hypersensitivity reactions Sulfonamides  sulfasalazine • sulfadiazine • cotrimoxazole Indications: Tx of rheumatoid arthritis, ulcerative colitis Action: blocks cellular metabolism of PABA for folic acid synthesis of susceptible grampositive & gram-negative baceria (bacteriostatic) Monitor for:    

IX.

hepatotoxicity nephrotoxicity Stevens- Johnson syndrome CNS effects & BM depression

Tetracyclines  tetracycline • doxyclcine • minocycline Indications: Tx of various infections, acne Action: inhibit protein synthesis Monitor for:    

damage teeth & bones GI effects BM suppression, photosensitivity & superinfections make oral contraceptives ineffective

X. Antituberculosis drugs a. 1st line drugs  isoniazid (INH)

• rifampin • ethionamide • rifapentine b. 2nd line drugs • ethambutol • pyrazinamide c. 3rd line drugs • capreomycin • cycloserine Indication: Tx & prophylaxis of tuberculosis

Monitor for:  discoloration of body fluids  hepatotoxicity  peripheral neuritis XI. Leprostatic drugs • dapsone • clofazimine • thalidomide

To Prevent Drug- resistant strains of bacteria: • use antibiotics cautiously • complete full course of therapy • avoid saving antibiotics for self-medication