Amino-glycosides Lecture Notes
Overview
- Aminoglycosides are antibiotics targeting mainly gram-negative microorganisms.
- They have a bactericidal effect, meaning they kill bacteria rather than merely inhibiting their growth.
Targeted Bacteria
- Gram-negative bacteria:
- E. coli
- Klebsiella pneumoniae
- Pseudomonas aeruginosa
- Serratia marcescens
- Enterobacter
- Gram-positive bacteria: Limited effect, except on:
- Staphylococcus aureus
- Enterococcus
- Mycobacteria infections:
- Mycobacterium tuberculosis
Clinical Uses
- Treatment for:
- Septicemia
- Severe urinary tract infections
- Infections in eyes, ears, bones, abdomen, pelvic areas
- Endocarditis
- Severe hospital-acquired pneumonia
Combination Therapy
- Often used with other antibiotics like Penicillin for a synergistic effect.
- Penicillin allows aminoglycosides to penetrate cell walls more effectively.
Medication Mnemonic: GNATS
- G: Gentamicin
- N:Neomycin
- *A: Amikacin
- T: Tobramycin
- S: Streptomycin
Administration
- Preferably given via parenteral routes (IM or IV).
- Exceptions:
- Tobramycin: Inhalation for cystic fibrosis lung infections.
- Neomycin: Oral for targeting gut bacteria, e.g., hepatic encephalopathy or bowel surgery prep.
Mechanism of Action
- Inhibit protein synthesis by targeting the 30S subunit of ribosomes.
- Bind to the 'A' site of 30S, causing misreading of genetic code.
- Result in production of nonfunctional "junky" proteins, leading to bacterial death.
- Nursing Considerations
- Confirm no allergies and obtain necessary cultures.
- Monitor peak and trough levels to guard against toxicity.
- Peak:Highest concentration; check 1 hour after IM or 30 minutes post IV infusion.
- Trough:Lowest concentration; check right before next dose.
- Indicators of effectiveness:
- Fever reduction
- Stable blood pressure and heart rate
- Normal white blood cell count
Toxicity and Side Effects
- Nephrotoxic (Kidney Injury):
- Reversible if monitored carefully.
- Monitor urine output and renal function tests (BUN, creatinine levels, GFR).
- Ototoxic (Ear Injury):
- Often irreversible. Increased risk with concurrent ototoxic drugs (e.g., Loop Diuretics).
- Watch for hearing loss, tinnitus, dizziness.
- Neuromuscular Blockade:**
- Can cause muscle weakness and respiratory failure.
- Special caution in patients with neuromuscular disorders or using neuromuscular blocking drugs.
For further details on antibiotics, refer to additional lectures in the series.