Aminoglycosides

Question 1

MOA

Answer 1

• Active against gram -ve + some gram +ve bacteria - not anaerobe
• Binds irreversibly to bacterial ribosomes (bactericidal)
• Broad spec

Question 2

Examples of abx

Answer 2

• Gentamicin (choice of drug)
• Neomycin (parenteral route toxic, use: bowel sterilization)
• Streptomycin (Use: TB)
• Tobramycin (inhaler: pseudomonal infection in cystic fibrosis

Question 3

What is the indication of gentamicin?

Answer 3

• Septicaemia
• Endocarditis
• Hospital acquired pneumonia
• Pseudomonas aeruginosa infection

Question 4

Route of gentamicin?

Answer 4

Parenteral

Question 5

What is the therapeutic index of gentamicin?

Answer 5

• 5/10MG/L POST DOSE
• <2MG/L PRE DOSE
• Endocarditis: post dose 3-5mg/L and <1mg/L pre dose
• Monitoring: Parenteral administration, Patient groups: elderly, renal impairment, obesity, cystic fibrosis, high dose, pregnancy

Question 6

What is the dose of gentamicin?

Answer 6

• Loading and maintenance doses are calculated using a patient’s weight and renal function
• To avoid excessive doses in obese patients, use ideal weight for height and closely monitor
• OD (Avoid: severe RI <20ml HACEK, gram +ve endocarditis, burns >20%)
• Multiple daily (Monitor after 3 to 4 doses, dose change, RI: more frequent + earlier)
• Post dose too high: red dose
• Pre dose too high: inc interval

Question 7

Gentamicin and pregnancy

Answer 7

Avoid - ototoxicity during 2nd + 3rd trimester

Question 8

Side effects of gentamicin

Answer 8

Ototoxicity

Nephrotoxic

Neuromuscular
- CI: Myasthenia gravis

Peripheral neuropathy
MHRA: gentamicin histamine related adverse reactions with some batches - cause allergies

Question 9

What are the interactions of gentamicin?

Answer 9

Ototoxicity
- Loop diuretic - separate dose by long period
- Platin + vinca alkaloid chemo

Nephrotoxicity
- Ciclosporin + tacrolimus
- NSAID
- Methotrexate
- Vancomycin
- Platin chemo