Miscellaneous Antibiotics

1. Miscellaneous Antibiotics Polymyxins • Active against gram-negative including pseudomonas. • Polymyxin B is only available. • Bactericidal inhibits cell wall synthesis. • Used only topically . • Highly nephrotoxic.

2. Spectinomycin • Bactericidal ,inhibits protein synthesis by binding to 30S ribosomal subunits. • Active against gram positive & gram negative organisms. • Rapidly absorbed after intramuscular injection. • Excreted through kidney .

3. Clinical uses • As an alternative treatment for drug- resistant gonorrhea or gonorrhea in penicillin –allergic patients. • No cross-resistance with other drugs used in gonorrhea. • A single intramuscular dose is given

4. Adverse effects • Pain at the site of injection • Fever And nausea • Nephrotoxicity ( rare )

5. Clindamycin • Active against gram-positive cocci • Gram negative anaerobic organisms • Inhibits protein synthesis by binding to 50S ribosomal subunits.

6. Pharmacokinetics • Given orally or intravenously • Highly bound to plasma proteins • Distributes well into all body fluids & tissues except brain &CSF. • Penetrates well into abscess & is taken up by phagocytic cells.

7. Metabolized by the liver. • Both active drug & active metabolites are excreted in bile & urine • No dosage adjustment is needed for renal failure.

8. Clinical uses • Severe anaerobic infections ( bones and joints) . • Conjunctivitis. • In combination with aminoglycoside or cephalosporin to treat penetrating wounds of the abdomen & the gut. • Infections in female genital tract ( septic abortion ,pelvis abscess ).

9. For prophylaxis of endocarditis in patients with valvular heart disease • Plus primaquine is an effective alternative to co-trimoxazole for moderate or severe pneumocystis jiroveci pneumonia in AIDS patients

10. Adverse Effects • Diarrhea , nausea, Skin rash • Antibiotic-associated colitis • Impaired liver function • Neutropenia ( not common )

11. Vancomycin • Bactericidal • Inhibits bacterial cell wall synthesis • Active on gram-positive bacteria including β-lactamase producer & those resistant to methicillin.

12. Pharmacokinetics • Poorly absorbed from GIT • Slow IVI is used for treatment of systemic infections. • Widely distributed • Cerebrospinal fluid levels are achieved in meningeal inflammation • Excreted mainly through renal route

13. Clinical uses • Endocarditis or sepsis mainly caused by methicillin –resistant staphylococci. • Alternative to penicillin in enterococcal endocarditis( in combination with gentamicin). • Meningitis( in combination with cephalosporin) • Orally only for the treatment of antibiotic -associated enterocolitis

14. Adverse effects • Phlebitis at the site of infusion • Fever • Ototoxicity & nephrotoxicity ( not common). • Red man or red neck syndrome. • Hypotension

15. Bacitracin • Bactericidal • Inhibits cell wall synthesis • Active against gram +ve organisms • Usedonly topically in skin ,eye ,nose infections . • As ointment in combination with polymyxin or neomycin for mixed bacterial infections. • As solution in saline for irrigation of joints, wounds or pleural cavity.

16. Adverse Effects • Highly nephrotoxic producing proteinuria, hematuria • Hypersensitivity reactions

17. Teicoplanin • Similar to vancomycin in : Mechanism of action Antibacterial activity • Given I.M. or I.V. • long half-life(45-70 h). once daily.

18. Cycloserine • Bactericidal • Inhibits bacterial cell wall • Effective on gram- positive & gram- negative organisms as well as M.tuberculosis. • Rapidly absorbed orally • Widely distributed in body tissues & fluids. • Excreted as active form in urine • Used in treatment of pulmonary & extrapulmonary tuberculosis • C.N.S. toxicity ( headaches, tremors, acute psychosis, convulsions) • Contraindicated in epileptic & psychotic patients