L41 - IV Administration 1 Flashcards
What are the different types of injections?
- parenteral
- IV administration
- IV bolus
What are parenteral injections?
Sterile preparation of drugs to be injected through one or more layers of skin or mucous membrane
What are IV administrations?
- formulation directly injection into a vein
- ensure ALL dose enters systemic circulation
What is IV bolus?
Solution of drug directly injected in vein by syringe/needle over a short period of time
What are facts about IV bolus?
- gets high conc of the drug very fast
- useful for emergency treatments
- consider monitoring toxicity
What are ADME processes like in IV bolus injections?
- no absorption, only disposition
- metabolism into metabolites
- excretion by urine, sweat, saliva, bile
What are the different phases in plasma profile for IV bolus administration?
- distribution phase
- elimination phase
What is the distribution phase in the IV bolus administration plasma profile?
- decline in plasma levels
- determined by distribution of drug to tissues
What is the elimination phase in the IV bolus administration plasma profile?
- equilibrium of distributino plasma-tissue achieved
- decline plasma levels primarily due to loss of drug from the body
What is distribution phase like?
- very short
- equilibrium of distribution plasma-tissue achieved very fast
What happens when distribution phase very shorts. Bc eq of distribution achieved evry fast?
- only elimination phase observed
- body acts as one compartment from time 0
- use one compartment model
What is the one compartment model?
- most frequently used
- drug assumed to rapidly/instantaneously distribute into homogenous fluid vol in the body
- simple model - only accounts for drug elimination
what is the two compartment model?
- drug rapidly distributes to central compartment - plasma and tissue
- takes time to distribute to peripheral compartment - deeper tissue
- accounts for drug distribution and drug elimination
What are assumptions made in the one compartment model?
- volume of the compartment equals volume of distribution of the drug
- elimination is first order - k = rate constant
- elimination follows linear kinetics
What is the equation for one compartment model as first order?
Da/dt = -k x A
What is the equation for one compartment model as first order? (Integrated)
- A = A0 x e^-kxt (eq2)
- lnA = lnA0 - k x t (eq3)
what is the rate of elimination like for one compartment model?
- directly proportional to the amount od drug present
- elimination rate constant has units of time-1
What is k in one compartment model?
- fractional rate of drug removal
- k = rate of elimination/A
What is the eqn for one compartment models according to concentration profiles?
- C = C0 x e^-kxt (eq 4)
- lnC = lnC0 -kxt
What does eq2 tell us?
- amount of drug in the body after IV bolus inject
- t = 0, A = A0 = Dose
- t = t, A = A0 x e^-kt
What does eqn 4 tell us?
- concentration of drug in the body after IV bolus inject
- t = 0, C = C0 = A0 / V = dose / V
- t = t, C = C0 x e^-kt
How do you estimate k from IV bolus data?
- use linear form of eq2 (ln version)
- calculate gradient = k
