Amoxicillin (amoxycillin)

Amoxicillin (aka amoxycillin)

[one tablet 6 cents; 1 vial for IV injection $2.17]

ADMINISTRATION ROUTES:

• IV, PO, NG

ALTERNATIVE NAMES:

• Apo-Amoxi , Ospamox, Ranbaxy-Amoxi, Ibiamox

ICU INDICATIONS:

1. treatment of infections caused by susceptible organisms
2. empirical treatment to cover enterococcus

PRESENTATION AND ADMINISTRATION:

• IV:
  1g vial (powder). Dilute to total of 5ml if part dose is required (making concentration of 200mg/ml). Inject slowly over 3-4 minutes or in 100ml of compatible fluid over 30-60 minutes.
  Compatible for 6 hours with normal saline, 3 hours with Hartmanns, 1 hour with D5W and glucose and sodium. (note that amoxicillin is less stable in solutions that contain glucose so it is preferable to avoid these solutions).
  Store at room temperature

• PO / NG:
  Apo-Amoxi 250mg tablets & 500mg tablets (red/gold, marked APO and strength), Ospamox capsules 500mg capules (yellow), Ospamox suspension (125mg/5ml and 250mg/ml), Ranbaxy-Amoxi (125mg/5ml and 250mg/5ml), Amoxil paediatric drops (125mg/1.25ml), Ospamox paediatric drops (100mg/ml). administration.

• DOSAGE:
  IV:
  1-2gm IV Q6hrly
  PO:
  500mg-1gm Q8hrly
  Liquid is preferred for NG

DOSAGE IN RENAL FAILURE AND RENAL REPLACEMENT THERAPY:

• Dose in renal impairment [GFR (ml/min)]
  <10: 500mg every 8 hours
  10-20: dose as in normal renal function
  >20-50: dose as in normal renal function
• Dose in renal replacement therapy
  CAPD: 500mg every 8 hours
  HD: 500mg every 8 hours
  CVVHDF: dose as in normal renal function

DOSAGE IN PAEDIATRICS:

• IV:
  Severe infections:
  1st week of life 50mg/kg 12hrly; otherwise 50mg/kg 6hrly

CLINICAL PHARMACOLOGY:

• Amoxicillin is bactericidal against susceptible organisms during the stage of active multiplication. It acts through the inhibition of biosynthesis of cell wall mucopeptide.
• Amoxicillin has been shown to be active against most strains of the following microorganisms:
  Aerobic Gram-Positive Microorganisms:
  Enterococcus faecalis. Staphylococcus spp*. (beta-lactamase-negative strains only). Streptococcus pneumoniae.
  *Staphylococci which are susceptible to amoxicillin but resistant to methicillin/oxacillin should be considered as resistant to amoxicillin.
  Aerobic Gram-Negative Microorganisms:
  Escherichia coli (beta-lactamase-negative strains only). Haemophilus influenzae (beta-lactamase-negative strains only). Neisseria gonorrhoeae (beta-lactamase-negative strains only). Proteus mirabilis (beta-lactamase-negative strains only).
• Amoxicillin diffuses readily into most body tissues and fluids, with the exception of brain and spinal fluid, except when meninges are inflamed.

CONTRAINDICATIONS:

1. A history of allergic reaction to any of the penicillins is a contraindication.

WARNINGS

• Anaphylaxis:
  Penicillins are a common cause of anaphylactic reactions
• Pseudomembranous colitis:
  Pseudomembranous colitis has been reported with nearly all antibacterial agents, including amoxicillin, and may range in severity from mild to life-threatening. Therefore, it is important to consider this diagnosis in patients who present with diarrhoea subsequent to the administration of antibacterial agents.

PRECAUTIONS

• General:
  Prescribing Amoxicillin in the absence of a proven or strongly suspected bacterial infection or a prophylactic indication is unlikely to provide benefit to the patient and increases the risk of the development of drug resistant bacteria.
  
• Laboratory Tests:
  No tests in addition to routine ICU tests are required.
• Drug/Laboratory Test Interactions:
  None noted.

IMPORTANT DRUG INTERACTIONS FOR THE ICU

• None of significance

ADVERSE REACTIONS

• Body as a Whole:
  Serum sickness like reactions, Anaphylaxis
• Digestive System:
  Nausea, vomiting, diarrhea, and hemorrhagic/pseudomembranous colitis. Hepatic dysfunction including cholestatic jaundice, hepatic cholestasis and acute cytolytic hepatitis have been reported.
• Nervous System:
  Reversible hyperactivity, agitation, anxiety, insomnia, confusion, convulsions, behavioral changes, and/or dizziness have been reported rarely.
• Skin:
  Stevens-Johnson Syndrome, exfoliative dermatitus, toxic epidermal necrolysis, acute generalized exanthematous pustulosis, hypersensitivity vasculitis and urticaria have been reported
• Haematological System:
  Anaemia, including hemolytic anaemia, thrombocytopaenia, thrombocytopenic purpura, eosinophilia, leukopaenia, and agranulocytosis have been reported during therapy with penicillins.