Aminoglycosides
Aminoglycosides
For Local action: Kanamycin, Neomycin
For Systemic action: Streptomycin, Gentamicin,
Tobramycin, Amikacin....
Aminoglycosides
Common Properties
• Poor absorption from GIT
• Synergistic action if combined with β lactam antibiotics
• ...
Aminoglycosides
Mechanism of Action
• Bind to 30 S subunit of ribosomes, inhibit initiation
complex=> misreading of mRNA, ...
Aminoglycosides
Uses:
Streptomycin - Tuberculosis, Brucellosis, Plague & enterococcal
endocarditis.
Gentamicin
• ( Along w...
Macrolides
Macrolides
• Erythromycin, Clarithromycin & Azithromycin
Mechanism of action:
• Bind 50 S ribosomal RNA, inhibits protein ...
Macrolides
Erythromycin
• Effective against Mycoplasma, Chlamydia, Legionella,
Campylobacter, Gm+ve & some Gm-ve organisms...
Macrolides
Adverse effects:
• Vomiting & Diarrhea
• Acute Cholestatic hepatitis (Erythromycin estolate)
• Skin rashes
Drug...
Clarithromycin
• Same antibacterial spectrum & uses as erythromycin.
• Less GI upset & less frequent dosing i.e. administe...
Azithromycin
• Similar antibacterial spectrum, but is more active against H
influenza, Moraxella catarrhalis, & Neisseria
...
Antitubercular drugs
Tuberculosis
Tuberculosis is a chronic granulomatous disease caused by
mycobacterium tuberculosis bacteria affecting lung...
Anti-TB drugs
First line drugs
1. Isoniazid (INH)
2. Rifampicin
3. Pyrazinamide
4. Ethambutol
5. Streptomycin
All are bact...
Anti-TB drugs
INH
Mech of action:
• Inhibits synthesis of mycolic acids, an essential component of
mycobacterial cell wall...
Anti-TB drugs
PYRAZINAMIDE
• More active at acidic pH effective only against intracellular
bacilli (macrophages)
Adv effec...
Anti-TB drugs
STREPTOMYCIN
Mech of action;
• Binds S 12 subunit of ribosomal proteins & inhibits bacterial
protein synthes...
Treatment of Tuberculosis
SHORT COURSE CHEMOTHERAPY
Combination therapy:
• Rapid killing of the organisms, ↓ resistance & ...
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5 aminoglycosides,macrolides, anti tb dental

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Pharmacology
Third Year

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5 aminoglycosides,macrolides, anti tb dental

  1. 1. Aminoglycosides
  2. 2. Aminoglycosides For Local action: Kanamycin, Neomycin For Systemic action: Streptomycin, Gentamicin, Tobramycin, Amikacin. For Both routes; Gentamicin, Tobramycin
  3. 3. Aminoglycosides Common Properties • Poor absorption from GIT • Synergistic action if combined with β lactam antibiotics • Show Concentration dependent killing • Post antibiotic effect –Persistent killing of bacteria even below MIC, greater effect with single large dose than small multiple doses • Narrow margin of safety • Exhibit Ototoxicity, Nephrotoxicity, & Neurotoxicity • Unchanged excretion by kidneys, dosage adjustment or discontinuance in renal impairment
  4. 4. Aminoglycosides Mechanism of Action • Bind to 30 S subunit of ribosomes, inhibit initiation complex=> misreading of mRNA, non functioning monosomes Adverse effects: • Ototoxicity ( irreversible) • Nephrotoxicity ( reversible) > 5 days of therapy • Neuro Muscular blockade • Teratogenicity=> Neonatal deafness. Contraindications - Pregnancy
  5. 5. Aminoglycosides Uses: Streptomycin - Tuberculosis, Brucellosis, Plague & enterococcal endocarditis. Gentamicin • ( Along with β lactams) – Sepsis, Pneumonia, & Enterococcal endocarditis • Topical: Conjunctivitis, Wounds, Burns Neomycin - Topically-infective wounds, Amikacin ( Resistant to many inactivating enzyme) • Multi Drug resistant Tuberculosis.
  6. 6. Macrolides
  7. 7. Macrolides • Erythromycin, Clarithromycin & Azithromycin Mechanism of action: • Bind 50 S ribosomal RNA, inhibits protein synthesis by blocking aminoacyl translocation & initiation complex (bacteriostatic) Resistance • Efflux pump mechanism & ribosomal protection by methylase • Drug metabolising esterases ( Enterobacteria)
  8. 8. Macrolides Erythromycin • Effective against Mycoplasma, Chlamydia, Legionella, Campylobacter, Gm+ve & some Gm-ve organisms Pharmacokinetics: • Food interferes with the absorption • Erythromycin stereate & esters are acid resistant hence better absorbed, erythromycin estolate is best absorbed. Uses • Community acquired pneumonia (Mycoplasma pneumoniae) • Diphtheria, ( Corynebacterium Diphtheriae) • Infections due to Chlamydia, Legionella & Campylobacter • Prophylaxis against endocarditis during dental procedures in patients with valvular heart disease.
  9. 9. Macrolides Adverse effects: • Vomiting & Diarrhea • Acute Cholestatic hepatitis (Erythromycin estolate) • Skin rashes Drug Interactions: • Inhibition of CYP 450 enzymes: ↑serum concentration of theophylline, oral anticoagulant, cyclosporine etc.
  10. 10. Clarithromycin • Same antibacterial spectrum & uses as erythromycin. • Less GI upset & less frequent dosing i.e. administered twice daily Uses • Eradication of H pylori in the treatment of peptic ulcer. • Prophylaxis & treatment of M avium complex, toxoplasmosis
  11. 11. Azithromycin • Similar antibacterial spectrum, but is more active against H influenza, Moraxella catarrhalis, & Neisseria • Because of its long half-life, a single dose is effective (once daily) and reduce the duration of treatment • Does not inhibit CYP 450 enzymes, hence free from drug interactions Uses • Community acquired pneumonia, • Urogenital infections caused by Chlamydiae trachomatis
  12. 12. Antitubercular drugs
  13. 13. Tuberculosis Tuberculosis is a chronic granulomatous disease caused by mycobacterium tuberculosis bacteria affecting lungs causing pulmonary tuberculosis. It may infect many other organs of the body, GIT, lymph nodes, CNS, skin, bones etc
  14. 14. Anti-TB drugs First line drugs 1. Isoniazid (INH) 2. Rifampicin 3. Pyrazinamide 4. Ethambutol 5. Streptomycin All are bactericidal except Ethambutol (bacteriostatic) Second line drugs 1. Ethionamide 2. Para amino salicylic acid 3. Cycloserine 4. Clarithromycin 5. Capreomycin All are bacteriostatic except Capreomycin (bactericidal)
  15. 15. Anti-TB drugs INH Mech of action: • Inhibits synthesis of mycolic acids, an essential component of mycobacterial cell walls. Adv effects: • Peripheral neuritis (prevented by Pyridoxine (B6) ) • Hepatotoxicity • Hemolysis in G6PD deficiency patient RIFAMPICIN Mech of action: Inhibits DNA-dependent RNA polymerase, thereby blocking production of RNA. Adv effects: • Orange discoloration of urine and other body fluids • Flu like syndrome, • Hepatitis
  16. 16. Anti-TB drugs PYRAZINAMIDE • More active at acidic pH effective only against intracellular bacilli (macrophages) Adv effects: • Hyperuricemia (precipitates gouty arthritis) • Teratogenicity -Spina bifida (contraindicated in pregnancy) ETHAMBUTOL • Inhibits Arabinosyl transferase involved in polymerization of Arabinoglycan ( Myco cell wall) Adv effects; Retrobulbar Optic neuritis=>loss of visual acuity & Colour blindness hence contraindicated in children <8 yrs
  17. 17. Anti-TB drugs STREPTOMYCIN Mech of action; • Binds S 12 subunit of ribosomal proteins & inhibits bacterial protein synthesis • Effective against extracelluar organisms • Given IM Adv effects: • Ototoxicity ( Vertigo & Deafness), nephrotoxicity, & neurotoxicity Neonatal deafness (contraindicated during pregnancy)
  18. 18. Treatment of Tuberculosis SHORT COURSE CHEMOTHERAPY Combination therapy: • Rapid killing of the organisms, ↓ resistance & ↓ duration of therapy Initial intensive phase (rapid killing) 2-3 months Continuation phase (elimination of remaining bacilli) 4-6 months • Initial Phase Continuation Phase Total duration (months) • 2 HRZE (S) 4 HR 6 • 3 HRZE (S) 6 HR 9 H=INH, R=Rifampicin, Z=Pyrazinamide, E=Ethambutol, & S=Streptomycin

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