IV drug administration

IV drug administration

1. Indications

   • 100% bioavailability, fast, systemic, patient may be unconscious, may not be available in another form, high/constant blood level of medicine needed, more effective

2. Guidelines for safe administration

   • 5 rights: Right patient, medicine, route, dose & time

3. Hazards and complications

   • fear phobia/pain, infection/sepsis, thrombophlebitis, extravasation/infiltration, emboli, anaphylaxis/hypersensitivity, overdose
     • Red man syndrome: hypersensitivity reaction due to histamine release. Erythematous rash of neck, face & upper torso. diffuse burning, itching generalised discomfort. Rare cases: hypotension, angioedema, chest pain, dyspnoea
       • Vancomycin (MRSA treatment) can cause this.
       • Incidence reduced by slowing infusion rate & more dilute drug solution
   • insufficient mixing, stability of medicines in solution (light, temp, conc, pH), interaction of medicines with syringe/bag

4. Pharmacokinetics

   • Bioavailibility: faction of unchanged drug that reaches the systemic circulation. IV gives 100%
   • Infusion vs repeated injections: intermittant is overall similar shape to continuous infusion, average peak is same and takes same time to plateau
   • If drug is infused at a constant rate and no drug is removed from body then the graph of plasma conc against time would be a straight line
     • BUT drug is eliminated from body as soon as it is in the circulation via kidneys
       • For most drugs the amount of drug eliminated per unit time is related to the conc of the drug in the plasma (1st order kinetics). Higher conc --> more drug removed per unit time, lower conc --> less drug removed
         • THEREFORE graph of plasma conc against time for most infusion will bend towards a plateau when the rate in = rate out "steady state"
       • CLEARANCE (CL) : volume of blood cleared of a drug per unit time. Whilst amount of drug eliminated varies, CL is constant
         • Css Plasma steady state conc. depends on = rate of drug administered (Ko) /volume of plasma cleared of drug per unit time (CL)
           • Time taken to reach Css depends on elimination 1/2 life
             • t1/2 = ln2 x Vd / CL

5. Disadvantages

   • Increase cost & time to administer, requires trained staff & location, rapid onset of action, volume of fluid needed to dilute medicine (may already be overloaded), can cause discomfort/pain, health risks e.g. infection

6. Types

   • Peripheral venous catheters
   • Central venous catheters CVCs
     • Peripherally inserted CVCs
     • Skin-tunneled CVCs hickman & broviac lines)
   • Arterial catheters

7. Methods of administering

   • Continuous: stable drugs, short half life, time dependent effects, needed dedicated IV site
   • Intermittent infusion: unstable drugs, long half life, conception dependent effects, less compatibility concerns
   • Bolus injection: rapid response required, incompatible, unstable drug