PK + PC Flashcards
What are parenteral medicines?
Injections, infusions and implants
What are the three most common routes of injection through the skin?
Subcutaneous, intramuscular and intravenous
What are the other 7 parenteral routes?
- intradermal
- intrathecal (into cerebrospinal fluid)
- epidural
- intra-articular (into synovial fluid)
- intracardiac
- intra-arterial
- intraocular
What are the 8 advantages of parenteral formulations?
- Immediate physiological response (IV route) for acute medical situations
- Drugs which have poor bioavailability or are rapidly degraded within GI tract
- Unconscious/uncooperative patients, patients with nausea/vomiting
- Control of dosage and frequency of administration by trained medical staff (an exception being self-administration of insulin)
- Requirement for localized effect
- Correction of electrolytes
- Range of drug release profiles
- Total parenteral nutrition (TPN)
What are the 5 disadvantages of parenteral formulations?
- More complicated and expensive
- Skill of administration
- Pain on administration
- Allergy to the formulation
- Difficult to reverse the effects
What are the 6 types of excipients used in paraenteral formulations?
- co-solvents
- surfactants
- buffers
- perservatives
- anti-oxidants
- tonicity agents
What are the 4 colligative properties?
- Vapour pressure depression
- Boiling point elevation
- Freezing point depression
- Osmotic pressure
What is vapour pressure depression?
Addition of a solute to a solvent, reduces the vapour pressure above the liquid
What is boiling point elevation?
The dissolution of a solute in a solvent increases the boiling point of the solution:
ΔTb= Kb m
What is freezing point depression?
The dissolution of a solute in a solvent decreases the freezing point of the solution:
ΔTf= Kf m
What is osmotic pressure for non-electrolyte solutions?
n R T = c R T
———- .
V
What is osmotic pressure for electrolyte solutions?
i c R T
What is osmolality?
number of osmoles/kg of solvent (i.e., water)
What is osmolarity?
number of osmoles/litre of solution
What is Isosmoticity?
if two solutions are separated by a perfect semi-permeable membrane and there is no net movement of solvent, the solutions are Isosmotic
What is Isotonicity?
solute conc inside = solute conc outside
What is the result of excessive infusion of isotonic formulations?
possible increase in extracellular
fluid volume and circulatory overload
What is the result of excessive infusion of hypotonic formulations?
RBC swelling, haemolysis, water ingress in to cells and tissues, eventually water intoxication (convulsion, oedema)
What is the result of excessive infusion of hypertonic formulations?
numerous possible complications, e.g. rapid high % dextrose causes hyperglycaemia, glycosuria & intracellular dehydration, osmotic diuresis, water & electrolyte loss, dehydration and coma
How do you prepare an isosmotic solution using the freezing point depression method?
Using tables, calculate the ΔTf caused by the drug and all other components of the formulation in order to determine the ΔTf required from the adjusting substance
ΔTf (required) = 0.52 – ΔTf (components)
Tables provide experimentally-determined ΔTf values for different concentrations of drugs and excipients
Must be freezing point of -0.52 ºC
How do you prepare an isosmotic solution using the NaCl equivalents method?
The sodium chloride equivalent (ENaCl) of a solute is the mass of NaCl that lowers the freezing point of a solvent (water) to the same extent as 1 g of the solute
Experimentally-determined ENaCl values for drugs and excipients can be found in tables
Must be 0.9 % NaCl
How do you prepare an isosmotic solution using the White-Vincent method?
Water is added to the drug and excipients in a sufficient amount to form an isotonic solution
The preparation is then made to its final volume with an isotonic or buffered isotonic diluting vehicle
Must be 285 mOsm/litre
What are the 7 most commonly monitored drugs?
- anticonvulsants
- antiarrhythmics
- antiasthmatics
- immunosuppresives
- antidepressants
- antineoplasics
- antibiotics
What are the 5 reasons for requesting TDM?
- a narrow therapeutic range
- assessment of adherence
- toxicity suspected
- lack of response
- no clear observable endpoint to therapeutic success
