CBM - Antibiotics Flashcards
Antibiotics
PENICLLIN β-lactams
Indications
Benzylpennicilin (penicillin G) phenoxymethylpennicilin (penicillin V) INDICATION-
- acute pharyngitis,
- tonsillitis, sore throat,
- otitis media,
- oral infection,
- cellulitis,
- streptococcal (including pneumococcal ),
- erysipelas,
- clostridail infection,
- meningococcal, gonococcal,
- lyme disease, gas-ganrene
Antibiotics
MECHANISM OF ACTION
- β-lactams block bacterial cell walls and inhibit enzyme responsible for cross-linking peptidoglycan in bacterial cell.
- This weakens cell wall preventing them from osmotic gradient.
- They diffuse well into body tissue and fluid, but penetration into the CSF is poor except when meninges are inflamed.
- Excreted in urine in therapeutic concentration Bacteria can resist the action of penicillin by making β-lactamase an enzyme which break β-lactams ring and prevent activity
Antibiotics
Beta-Lactams?
Dose?
Dose:
Benzylpennicilin (penicillin G) hydrolysis by gastric acid prevent GI absorption
IV OR IM 1.2g every 4-6hrly
Phenoxymethylpennicilin (penicillin V) orally
Adult 500mg 6hrly increase dose if necessary
Antibiotics
Side Fx (Beta-Lactams)?
- Allergy and cross-sensitivity ,30% of people have penicillin allergy can be fatal (anaphylactic reaction-bronchospasm, hypotension, rash, oedema, angioedema,
- CNS toxicity- encephalopathy, convulsion, coma can occur in high dose or where sever renal impairment delay excretion
- Patient with hx of hypersensitivity with penicillin may also react to other β-lactams abx including cephalosporins, Carbapenem
Antibiotics
Warnings (Beta-Lactams)?
- Dose reduction for pt with renal impairment
- Hx of allergy
- Accumulation of sodium from injection Benzylpennicilin (penicillin G) can occur renal failure
- High dose may cause neurotoxicity including cerebral irritation, convulsion and coma.
INTERACTION
Penicillin reduce renal excretion of methotrexate increasing risk toxicity
Antibiotics
Penicillin (Broad Spectrum)
Amoxicillin/Co-Amoxiclav
Indications
- sinusitis,
- otitis media,
- oral infection,
- respiratory track,
- acute bronchitis,
- UTI,
- CAP,
- salmonellosis,
- cellulitis,
- genito-urinary and abdominal infection,
- sepsis
CO-AMOXICLAV-due to β-lactamase producing strains where amoxicillin alone are not appropriate
CONTRA-INDICATION-hx of CO-AMOXICLAV associate hepatic jaundice or hepatic dysfunction
Antibiotics
Penicillin (Broad Spectrum)
Amoxicillin/Co-Amoxiclav
Side Fx
- GI upset diarrhoea
- Abx associated colitis
- Penicillin allergy
- Cholestatic Jaundice
Antibiotics
Penicillin (Broad Spectrum)
Amoxicillin/Co-Amoxiclav
Warnings/Interactions
- Reduce dose in pt with renal impairment risk of crystalluria
- Hx of penicillin allergy
- Monitor liver function in pt with liver impairment
INTERACTION
- Reduce renal excretion of methotrexate, increase toxicity
- Can enhance anticoagulant effect of warfarin by killing normal gut flora the synthesis vitamin K
Antibiotics
Penicillin (Broad Spectrum)
Amoxicillin/Co-Amoxiclav
Dose?
- AMOXICILIN orally –adult 500mg 8hrly
- CO-AMOCILAV-250/125 mg 8hrly, increase dose 500/125mg in severe infection
Antibiotics
Macrolides
Indications?
MACROLIDES -
- Have antibacterial spectrum that is similar but not identical to penicillin
- Erythromycin, azithromycin, clarithromycin (alternative to penicillin)
Indications-
- respiratory tract infection (mycoplasma pneumonia, skin,
- soft tissue and oral infection, otitis media,
- legionella infection,
- cambylobacteria enteritis, chlamydia)
Mechanism of action-
- Inhibits bacterial protein synthesis (BATERIOSTATIC ACTIVITY).
- They bind to the 5os subunit of bacterial ribosome and block translocation, a process required for elongation of polypeptide chain, inhibition of protein synthesis
Antibiotics
Macrolides
Dose?
Clarithromycin mostly prescribed:
- in the UK 250mg-500mg 2xdaily 7-14day
Erythromycin:
- 250-500mg 4x daily or 500-100mg for 5day
Antibiotics
Macrolides
Side Fx?
- QT prolongation
- Irritant- abdominal pain, nausea and vomiting, diarrhoea
- Ototoxicity at high dose
- Allergic antibiotic associated colitis
Antibiotics
Macrolides
Warnings?
Metabolized by the liver, small amount in the kidney:
- Avoid in severe hepatic /renal impairment
- Avoid in pregnancy/ breastfeeding except if benefit outweigh risk( manufacturers instruction)
- Prescribed with caution in taking other drugs that prolong OT interval eg amiodarone, antipsychotic drugs and SSRI, quinine Also interact with digoxin, theophylline, carbamazepine
Antibiotics
Macrolides
Interactions?
- Erythromycin and clarithromycin inhibit cytochrome p450 an enzyme in the liver.
- This reduces the metabolism of other drugs increasing their effects.
- Drugs metabolized by p450 enzymes eg warfarin there is an increased risk of bleeding.
- Statin- increase risk of myopathy
