Ai : Outline potential problems associated with additives used to make medications suitable for IV injection

  • IV medications are common to critical care practice

→ rapid admin/onset

→ delivery when unconscious possible

  • Additives added to drug preparations to:
    1. ↑ drug solubility (storage)
    2. Stabilise agent (prevents hydrolysis/oxidation)
    3. Maintain pH/osmolarity (soluble)
    4. Preserve (prevent contamination)

1) ↑ Drug Solubility

Emulsifiers

    • Soyabean oil (propofol) → Allergy, anaphylaxis, ↑calories, pain on injection

Solvents

  • Propylene glycol (phenytoin) → Thrombophlebitis, pain on injection, ↓BP 2° VD
  • Benzyl alcohol (diazepam) → peripheral VD & ↓inotropy @ large dose/rapid bolus
  • Freeze drying (vecuronium) → H2O causes hydrolysis of drugs → requires them to be freeze dried → contamination, ↑$$ of drug

2) Stabilisers (prevent hydrolysis/oxidation in storage)

  • Lethicin (propofol) → allergy
  • Sulphites (metabisulfite with adrenaline) → bronchospasm, anaphylacatoid (itch)

3) Maintain pH/Solubility

  • HCl (midazolam) maintains pH <4 → closes Midaz ring to make it ↑H2O soluble and allow easy storage
  • Sodium carbonate Na2CO3– (thio) → mixing with acid (atracurium) can cause precipitation/crystallisation

4) Preservatives (prevent contamination)

  • Parabens → present in multiple agents g. LA
    • Prevents yeast/fungal growth > bacteria
    • Low allergenicity
  • Benzyl alcohol (diazepam, hydrocortisone) → peripheral VD & ↓inotropy @ large doses