Anti-infective Drugs Flashcards
what are some examples of penicillin beta lactams?
Flucloxacillin
Amoxicillin
Benzylpenicillin
Penicillin V
what is the mechanism of action of penicillins?
Attaches to penicillin-binding-proteins on forming bacterial cell walls.
This inhibits the transpeptidase enzyme which cross-links the bacterial cell wall.
Failure to cross-link induces bacterial cell autolysis.
Amoxicillin provides some amount of gram-negative cover in addition to gram-positive drugs
what are the indications for penicillins? - specifically flucloxacillin and amoxicillin?
Different penicillins have different indications as different spectrum of cover.
Flucloxacillin provides Staphylococcus aureus cover whereas Amoxicillin does not.
Flucloxacillin: Soft tissue infection; Staphylococcal endocarditis; Otitis externa
Amoxicillin: Non-severe community acquired pneumonia
list some side effects of penicillins?
diarrhoea
vomiting
liver function impairment
hypersensitivity reactions
what is important clinically regarding Pharmacokinetics/dynamics for penicillin?
good oral absorption
Flucloxacillin: Beta-lactamase stable/insensitive. (Beta-lactamase producing bacteria are vulnerable to it)
Amoxicillin: Beta-lactamase susceptible. (Beta-lactamase producing bacteria are resistant to it).
what info should be given to a patient before commencing on a penicillin?
Return if symptoms persists after the course of antibiotics, may be infected with resistant organism.
Diarrhoea is a common side effect.
Report any incidence of a rash after use – risk of hypersensitivity reactions.
how is resistance in bacteria that secrete beta lactamase overcome?
by a beta lactamase inhibitor given with the penicillin e.g. clavulanic acid along with amoxicillin - co-amoxiclav
what are some examples of cephalosporin beta lactams?
ceftriaxone
cephalexin
what is the MoA of cephalosporins?
Attaches to penicillin-binding-proteins on forming bacterial cell walls.
Inhibiting transpeptidase enzyme which cross-links the bacterial cell wall.
Failure to cross-link induces bacterial cell autolysis.
Less susceptible to beta-lactamases than penicillins.
Provides both gram-positive and gram-negative cover.
What are the indications for cephalosporins?
Serious infection: septicaemia / pneumonia / meningitis
list some side effects of cephalosporins
Hypersensitivity reactions
Antibiotic-associated C.Difficile diarrhoea
Liver function impairment
what is important clinically regarding Pharmacokinetics/dynamics for cephalosporins?
renal excretion
longer half life - needs to be given once daily
what info should be given to a patient before commencing on a cephalosporin?
diarrhoea is a common side effect
report incidence of a rash after use
what is an example of a glycopeptide?
vancomycin
what is the MoA of vancomycin?
bactericidal - inhibiting cell wall synthesis in gram positive bacteria
what are the indications for vancomycin?
severe gram positive infections
MRSA
severe C. diff infection
list some side effects of vancomycin:
- Fever
- Rash
- Local phlebitis at site of injection
- Nephrotoxicity
- Ototoxicity (Rare)
- Blood disorders, including neutropenia
- Anaphylactoid reaction “red-man syndrome” if infusion rate too fast
what is important clinically regarding Pharmacokinetics/dynamics for glycopeptides?
can be given as continuous IV or pulsed infusion
long duration of action - can be given every 12 hours
therapeutic monitoring as narrow therapeutic window
what info should be given to a patient before commencing on vancomycin?
Risk of kidney damage.
Patients should report any changes in hearing.
Regular blood tests required for monitoring.
what is an example of an aminoglycoside?
gentamicin
what is the MoA of gentamicin?
binds to 30s ribosomal subunit, inhibiting protein synthesis, inducing a prolonged post-antibiotic bacteriostatic effect
bactericidal on cell wall causes rapid killing early on
synergistic when used with other antibiotics
what are the indications for gentamicin?
Severe gram-ve infections (e.g. biliary tract infection, pyelonephritis, hospital-acquired pneumonia).
Some severe gram+ve infections (e.g. soft tissue infection and endocarditis).
list the side effects of aminoglycosides?
nephrotoxicity
ototoxicity
^related to prolonged exposure to high conc.
what is important clinically regarding Pharmacokinetics/dynamics for aminoglycosides?
Give high initial dose to take advantage of rapid killing
Leave long dosing interval to minimise toxicity
Measure trough level to ensure gentamicin is not accumulating before giving more doses.
Try to limit use to approximately 3 days to minimise risk of side-effects.
what info should be given to a patient before commencing on gentamicin?
patient should report any change in hearing
risk of kidney damage so need to monitor drug levels and renal function
what is an example of a quinolone?
ciproflaxin
what is the MoA of a quinolone?
interferes with bacterial DNA replication and repair
broad spec bactericidal antibiotics, provides gram +ve and -ve cover
what are the indications for ciprofloxacin?
Gram negative bacterial infection Respiratory tract infection Upper urinary tract infection Peritoneal infection Gonorrhoea Prostatitis
what are some of the side effects of quinolones?
GI toxicity
QT wave prolongation
Clostridium difficile infection
Tendonitis (this is extremely rare a type B adverse drug reaction)
what info should be given to the patient before commencing on ciprofloxacin
risk of diarrhoea after use
what are some examples of macrolides?
clarithromycin
erythromycin
what is the MoA of macrolides?
binds to 50s ribosomal subunit
inhibits bacterial protein synthesis
what are the indications for macrolides?
Atypical organisms causing pneumonia/Severe CAP Severe campylobacter infection Mild/mod skin and soft-tissue infection Otitis media Lyme disease Helicobacter pylori eradication therapy
list the side effects of macrolides?
diarrhoea
vomiting
QT wave prolongation
ototoxicity with long-term use
what is important clinically regarding Pharmacokinetics/dynamics for macrolides?
Uses hepatic enzyme Cytochrome P450 pathway
Can interact with all drugs using this pathway, especially Simvastatin, Atorvastatin and Warfarin.
what info should be given to the patient before commencing on macrolides?
Risk of Diarrhoea
Senses of smell and taste may be disturbed during therapy.
Tooth and tongue discoloration may occur during therapy.
what is an example of an inhibitor of folate synthesis?
trimethoprim
what is the mechanism of action of inhibitors of folate synthesis?
inhibits folate metabolism pathway and leads to impaired nucleotide synthesis
therefore interferes with bacterial DNA replication
what are the indications for inhibitors of folate synthesis?
First line antibiotic in uncomplicated UTI.
Acute / chronic bronchitis
Pneumocystis pneumonia (PCP)
Good range of action against gram -ve and gram +ve bacteria. And some MRSA cover.
list the side effects of inhibitors of folate synthesis
Elevated serum creatinine
Hyperkalaemia
Depressed haematopoiesis
Rash and GI disturbance both relatively common
what is important clinically regarding Pharmacokinetics/dynamics for trimethoprim?
- Penetrates well into the prostate, suitable for men with uncomplicated UTI
- Avoid in the 1st trimester
- Resistant organisms are a major problem in clinical use.
- Hyperkalaemia is more common in patients with impaired renal function.
what info should be given to the patient before commencing on trimethoprim?
Blood tests required in those at risk of hyperkalaemia.
Return to the doctor if symptoms do not clear after trimethoprim course, resistance does occur.
Rash and GI disturbances are common adverse reactions.
what is an example of an anti-viral?
aciclovir
what is the MoA of aciclovir?
A guanosine derivative, converted to triphosphate by infected host cells.
Aciclovir triphosphate then inhibits DNA polymerase, terminating the nucleotide chain and inhibiting viral DNA replication.
what are the indications for anti-virals?
herpes simplex infection
varicella zoster infection
what are the side effects of aciclovir?
nausea
vomiting
local inflammation at infusion site (IV)
what is important clinically regarding Pharmacokinetics/dynamics for aciclovir?
Can be oral, IV or topical.
Penetrates well into the CSF with CSF concentrations being 50% concentration of that of plasma.
Excreted by the kidneys so dose adjustment is needed in renal impairment.
what info needs to be given to the patient before commencing on aciclovir?
multiple/repeat doses may be required in immunosuppressed patients
