T2i / 19B20: Compare the pharmacology of piperacillin-tazobactam and ciprofloxacin
19B20: Exam Report
Compare the pharmacology of piperacillin-tazobactam and ciprofloxacin.
58% of candidates passed this question.
This question was most effectively answered using a tabular format. Only a minority of candidates demonstrated a comprehensive knowledge of these level 1 drugs and very few candidates compared the two in areas which lent themselves to comparison. The spectrum of activity generally lacked detail. Few candidates mentioned that piperacillin-tazobactam had superior gram-positive cover, both have extensive gram-negative cover including Pseudomonas. Piperacillin-tazobactam is effective against anaerobes; whilst ciprofloxacin has some atypical cover against Mycoplasma.
The mechanism of action was generally well described for piperacillin; many candidates incorrectly stated the mechanism of action for ciprofloxacin, confusing the drug with a macrolide. Better answers included time- dependant and concentration-dependent killing. The concept of half-life was frequently confused with the dosing interval.
Minimal marks were awarded for “allergy” and “gastrointestinal side-effects”. Better candidates mentioned Liver function derangement, neutropenia, interstitial nephritis for piperacillin and tendonitis for ciprofloxacin.
T2i / 19B20: Compare the pharmacology of piperacillin-tazobactam and ciprofloxacin
Drugs
Tazocin
Ciprofloxacin
Comments
Class
Tazocin
Antipseudomonal
Beta-lactamase inhibitor
Mechanism: the beta lactamse inhibitor (tozobactam) uses itself as a substrate for the bacteria’s b lactamase, which leaves the piperacillin’s b-lactam ring free to bind to the penicillin binding proteins
Ciprofloxacin
Quinolone
Comments
Dose
Tazocin
4.5g tds
Ciprofloxacin
500-700mg q12-24h
Comments
Mechanism
Tazocin
Cell Wall Inhibitor
Ciprofloxacin
Bacteristatic & Bactericidal
Comments
MoA
Tazocin
- B lactam ring mimics shape of D-Ala-D-Ala sequence that is the substrate for cell wall transpeptidases
This is the final step in bac cell wall synthesis that allows cross linking
By pretending to be D-Ala-D-Ala, it binds transpeptidases -> inhibits enzyme activity → bac without cell wall → die
- Exerts bacterial autolytic effect
Inhibits certain penicillin binding proteins (PBP) related to the activation of autolysis →promotes bac lysis & cell death
Ciprofloxacin
Inhibits DNA gyrase enzymes
Promotes breakage of DNA
Commets
Time v Concentration
Tazocin
Time Dependent -> time spent above minimal inhibitory concentration determines efficacy
Ciprofloxacin
Combination concentration and time dependent killing
Comments
Post Dose Effect
Tazocin
Short 2hrs – bactericidal
Ciprofloxacin
Commets
Indication
Tazocin
V Broad Spectrum
Hospital acquired infections
Ciprofloxacin
UTI
Resp tract
Intra-abdm
Anthrax
Comments
Spectrum
Commets
Both have extensive G- cover
Cipro has some atypical cover
Tazocin has superior G+ cover
Tazocin
Covers
Staph auereus (methicillin susceptible)
Coag –ve Staph
Strep pneumonia
H influenza
Moraxella
Neisseria Meningitides
Neisseria gonnorrhoeae
E Coli
Pseudomonas aeruningosa
Doesnt
MRSA
VRE
Atypicals
Ciprofloxacin
Covers
G-
Enterobacter
H influenza
Haemophilus
N g & m
Atypicals –
Legionella
Excellent TB coverage
Doesnt
Almost no G+ cover
Commets
Both have extensive G- cover
Cipro has some atypical cover
Tazocin has superior G+ cover
PK
Tazocin
A
IV only
D
PPB 20%
Vd 0.2L/kg
M
Minor hepatic metabolism
E
Renally excreted
Needs dose adjusted in renal impairment
Ciprofloxacin
A
70% OBA. Delayed by food
D
20% PPB
M
4 metabolites, probably hepatic
E
Renal excretion of metabolites
Comments
Tazocin can only be administered IV
Cipro has good OBA
Both have similar PPB
Cipro is hepatically metabolised whereas Tazocin is renally cleared
AE
Tazocin
High Na+ load
Interacts w Vecuronium – prolongs neuromuscular blockade
Ciprofloxacin
CNS – headache, insomnia, dizziness, hallucinations
Renal – interstitial nephritis
CVS – QTC prolongation, TdP, arrhythmias
MSK – joint pain
Skin – toxic epidermal necrolysis
Drug Interaction – with warfarin, increases PT
Monitoring
Tazocin
UEC
Renal fn
LFTs
Ciprofloxacin
Renal fn
Comments
Both require monitoring of organ fn
Cipro will need monitoring of ECG & reconciliation of medications for drug interactions
- Author: Krisoula Zahariou