meningitis antibiotics mechanism of action
TRANSCRIPT
Antibiotics in Bacterial Meningitis
by Mario Wilmath, MD
Objectives
Describe the general mechanisms of antibiotic action.
Understand the antibiotics used in bacterial meningitis.
Describe the parenteral dosage forms and routes of administration of antibiotics.
Relate to case of John D.
Cell Wall Synthesis Blockade
Cephalosporins (3rd generation)Example: cefotaxime
Overview: Beta-lactam Increased activity and
distribution
MOA: Interference with cell wall
synthesis (transpeptidation) Activating autolytic enzymes
PenicillinsExample: PenG, oxacillin
Overview: Beta-lactam Resistance and allergy
MOA: Interference with final step in cell
wall synthesis (transpeptidation) Activating autolytic enzymes
http://www.itqb.unl.pt
http://www.itqb.unl.pt
Cell Wall Synthesis Blockade Example: Vancomycin
Overview: Treat beta-lactamase resistance Wide distribution
MOA: Large glycopeptide Hydrogen bonds to NAM and NAG subunits Inhibits murein synthesis and peptidoglycan cell wall
http://www.itqb.unl.pt
http://www.itqb.unl.pt
www.nlm.nih.gov
Disruption of Cell Membranes
Overview:
Selective toxicity to bacterial membrane.
MOA:
May disrupt membrane structure (sterols) or function (pores).
Examples: Polymixins
Imidazoles
http://content.answers.com
Inhibition of Protein SynthesisChlormaphenicol
Overview: Broad spectrum Used for penicillin allergy Bacteriostatic only
MOA: Binds 50S ribosomal unit Block peptidyl transferase Inhibit mitochondrial synthesis.
RifampinOverview: Wide distribution into CNS Prophylaxis for meningitis
MOA: DNA-dependent RNA polymerase
inhibition
http://wpcontent.answers.com
Inhibition of Nucleic Acid Synthesis
Example: Ciprofloxacin
Overview: » Quinolone» Poor CNS penetration » Cannot be used: Children or
pregnancy
MOA: » Inhibits bacterial DNA gyrase » Supercoiled DNA cannot relax» Transcription and replication
blocked
http://www.pharmainfo.net
www.pharmainfo.ne
Inhibition of Nucleic Acid Synthesis Example: Sulfisoxazole
Overview: » Sulfonamide: PABA-like structure » Only moderate tissue penetration
MOA: » Dihydropeteroate synthase:
Competitive inhibitor Substrate becomes nonfunctional folic acid
analogue
http://www.elmhurst.edu
Penicillin G
Powder Frozen solution IV preferred, supplement IM 250000 U/kg/d IV or IM q4-6h
x 7-14d
http://userweb.port.ac.uk/~norrismj/antimicrobial_agents/Penicillins.html
http://www.drsfostersmith.com/product/prod_display.cfm?pcatid=16196
Cefotaxime
Powder Frozen solution ADD-Vantage System IV or IM 150–225 mg/kg/d IV or IM q6-8h Case study: 250mg/kg/d IV q12h
http://www.appdrugs.com/ProductDetail.html?pfid=18&name=Cefotaxime_for_Injection_USP
Courtesy of Dr. Mobley’s lecture on parenteral delivery systems
Vancomycin
Powder Frozen solution IV Intrathecal / Intraventricular 50 – 60 mg/kg/d IV q6 – 8 h Case study: 60mg/kg/d IV
q6h
http://www.mrsapedia.com/vancomycin-and-mrsa/
Chloramphenicol
Powder IV or PO 75 – 100 mg/kg/d IV or
PO q6h
http://www.supplierlist.com/photo_images/53922/Chloramphenicol_Caps.jpg
http://www.apppharma.com/ProdJPGs/ChloramphenicolLg.jpg
Ciprofloxacin
Oral Nasal carrier state Prophylaxis 500 mg PO q12h X
5d
http://onlyhealth.wordpress.com/2009/09/16/generic-cipro-is-preeminent-antibacterial-drug/
Conclusion
The 4 mechanisms of action for antibiotics:
1. inhibit cell wall synthesis
2. membrane permeability
3. protein synthesis
4. nucleic acid synthesis
Case study received vancomycin + cefotaxime and his contacts received rifampin prophylaxis
References
Acute Bacterial Meningitis. Mace, SE. Emergency Medical Clinics of North America. Volume 26, issue 2, May 2008. Accessed Tuesday March 30, 2010 from http://www.mdconsult.com.lp.hscl.ufl.edu/das/article/body/192106220-2/jorg=journal&source=&sp=20587149&sid=0/N/638565/1.html?issn=0733-8627#tblfn3
Clinical Pharmacology. Accessed on Sunday March 28, 2010 from http://www.clinicalpharmacology-ip.com.lp.hscl.ufl.edu/default.aspx
Katzung BG and Trevor AJ. Examination and Board Review Pharmacology, 4th edition. Appleton & Lange. Norwalk, Connecticut. 1995.
RX List. Accessed on Sunday March 28, 2010 from http://www.rxlist.com/bicillin-c-r-drug.htm