The document discusses various antibiotics and their preparations, focusing on their mechanisms of action, antibacterial spectra, and clinical uses. Key agents include topical antibiotics like sulfacetamide, ciprofloxacin, polymyxins, bacitracin, and new classes such as oxazolidinones. It highlights specific applications for treating infections caused by Gram-positive and Gram-negative bacteria, as well as potential side effects associated with their use.

1. Miscellaneous Antibiotics
Dr. D. K. Brahma
Associate Professsor
Department of Pharmacology
NEIGRIHMS, Shillong

2. ???
• Name some antibacterial agents having
topical preparations
• Sulfacetamide sod. (20 – 30% eye drop & oint., Mafendie & Silver
sulfadiazine (1% cream)
• Ciprofloxacin eye/ear drop (3 mg/ml)
• Freshly prepared penicillin solution
• Chlorampheincol eye drop (0.4-0.5%), otic solution (10%), cream (10%)
• Gentamicin eye/ear drop (0.3%), 0.1% cream; Tobramycin & sisomycin
0.3% eye drop, Neomycin – skin cream-oint-eye oint-ear drop etc.

3. Polypeptide Antibiotics
• Low molecular weight cationic polypeptide
• Powerful bactericidal agents – toxicity
• Elaborated from bacteria
• Names –
1. Polymyxin B - Bacillus polymyxa
2. Colistin - B. Colistinus
3. and Bacitracin - Bacillus subtillis

4. Polymyxin B and Colistin
• Antibacterial spectrum: Gm -ve bacteria only,
except Proteus, Serratia and Neisseria
– Colistin more potent in Pseudomonas, Shigella and
Salmonella
• MOA: Rapidly acting bactericidal
– Detergent like action – high affinity for phospholipids
– Orient between phospholipid and protein layers –
membrane distortion or pseudopore formation
– Leakage of ions and amino acids etc. – also inactivate
endotoxins
– Exhibits synergism with other AMA - penetration

5. Polymyxin B and Colistin
• ADRs: No oral absorption or denuded skin absorption
– Applied topically – safe - no systemic effects or sensitization
– Orally ? - Nausea, Vomiting and diarrhea
– Systemic on parenteral – flushing and parasthesia (Histamine?),
Kidney damage neurological disturbances and NM blockade
• Preparations: Polymyxin B – in combination with neomycin
and bacitracin/hydrocortisone – powder, eye/ear drop and
ointment; Colistin – Dry syrup
• Uses:
– Topically: in combination with others in skin infections, burns,
otitis externa, conjunctivitis and corneal ulcer
– Orally: Gm-ve bacillary diarrhea – Salmonella, Shigella, E. coli
etc) in children and also pseudomonas superinfection enteritis

6. Bacitracin
• Bactericidal
• Source – Bacillus subtillis
• Spectrum: Gm +ve cocci and bacilli; also Neisseria and
H. influenzae
• MOA: Inhibits cell wall synthesis (Penicillin) – efflux of
ions
• Kinetics: Not absorbed orally, high toxicity parenterally
(kidney) – topical only
• Uses: Infected wounds – ulcers, eye infections – in
combination with neomycin and polymyxin
– Does not penetrate intact skin
– NEBASULF, NEOSPORIN

7. Others …
• Spectinomycin: Spectromyces spectabilis – narrow spectrum
antibiotic similar to aminoglycosides – effective against limited no.
of gm-ve bacteria
– MOA: Inhibits bacterial protein synthesis – 30S rhibozome
– Uses: IV - Drug resistant gonorrhoea / beta lactum allergy or
contraindicated
• Quinupristine/Daflopristine – semisynthetic antibiotic – like
macrolides and lincosamides -
• Streptogramins group – Gr. A and Gr. B – naturally occurring
bacteriostatic
• 30: 70 mixture – bactericidal – administered parenterally
– MOA: Inhibition of bacterial protein synthesis – (i) 50S fraction -
inhibition of incorporation of aminoacyl tRNA and mRNA translation
– Spectrum: Gm +ve cocci including MRSA, VRSA, VRE, Neisseria,
Legionella and Chlamydia pneumoniae – not in E. faecium
– Uses: Nosocomial MRSA, VRE and other resistant gm+ve infections

8. Mupirocin and Fusidic acid
• Mupirocin: Topical antibiotic - Obtained from Pseudomonas
(pseudomonic acid)
– Specturm: Gm +ve bacteria – Stre. pyogenes (sensitive penicillin &
resistant), Staph. aureus, MRSA
– Bacteriostatic – at high conc. bactericidal
– Uses: furunculosis, folliculitis, impetigo, infected insect bites and small
wounds
– Preparation – 2% ointment – local use only
– BACTROBAN, MUPIN, T-BACT
• Fusidic acid: narrow spectrum steroidal antibiotic – blocks protein
synthesis
– Effective against penicillinase producing Staph. aureus and few gm
+ve bacteria
– Uses: Boils, furunculosis and other cutaneous infections
– FUSIDERM, FUSIBACT

9. Oxazolindinone
• Linezolid - New Class of syntheic antibiotic - 2 rings –
Oxazolidine and Oxazoline
• Spectrum: Useful in resistant gm+ve coccal (aerobic and
anaerobic) and bacillary infection
– MRSA, VRSA, VRE, penicilin resistant – Strep. pyogens, Strep. Viridans,
Strep. pneumoniae, M. tuberculosis, Corynebacterium, Listeria,
Clostridia and Bact. Fragilis
• MOA: Binds to 23S fraction (p site) of 50S ribosome and
interfere with formation of N-formylmethionine – tRNA
(tRNAfMet
) -70S initiation complex
– Distorts tRNA binding site – overlapping of 50S and 30S ribosomal
subunits – stops protein synthesis – (Resistance – mutation of 23S)

10. Linezolid
• Kinetics: Completetly absorbed orally, metabolized non-
enzymatically and excreted in urine – half life – 5 hours
• Uses: Complicated and uncomplicated skin and soft tissue
infections, community and hospital acquired pneumonias,
bacteraemias and other gm+ infections
– However – hospital acquired pneumonias, febrile neutropenia, wound
infections others due to multidrug resistant gm +ve bacteria – VRE,
VRSA etc.
• ADRs: Mild – abdominal pain, nausea, taste disturbance
– Rash, pruritus, headache, oreal/vaginal candidiasis
– Neutropenia, thrombocytopenia and optic neuropathy
– MAO inhibitor

11. Khublei shibun