A patient requires an intravenous (IV) infusion of an active pharmaceutical ingredient (API) which
obeys the one-compartment pharmacokinetic model. The therapeutic plasma concentration (Ç) for
the API is 35 mg L'², the API's volume of distribution (v) is 18.4 L and the API's elimination constant
(k_) is 0.165 hr2.
Calculate a suitable infusion rate (in mghr² which will achieve the therapeutic
plasma concentration when administered over 30min.
Calculate the infusion rate (in mg hr² which will maintain the therapeutic plasma
concentration once steady state has been achieved by the loading infusion
performedin (a) above.
The maintenance infusion was terminated because the patient developed 20 % renal
failure due to the illness. The plasma concentration upon stopping was found to be
mg L' (i.e. ) Indicate how and why renal failure is likely to affect a patient's
plasma level of a drug substance.
Therapeutic drug monitoring determined Cp 5 hr after stopping the infusion to be
15.72mg L' Calculate kd and an appropriate infusion rate which would maintain the
therapeutic plasma concentration
The drug cournarin is metabolised to aconjugate as shown below:
(a) Draw the structure of metabolite A and identify the type of conjugate produced
(b) Discuss the conjugation enzyme involved, highlighting its subcellular localisation, cofactor
requirements and the biosynthetic pathway of the conjugate moiety
(c) The conjugate is further metabolised to a mercapturate as shown below: Draw the
structures of metabolites B and C and discuss their formation and excretion.
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1. For an intravenously administered drug, the bioavailability F will equal 1, since the drug is directly introduced to the bloodstream. If the patient requires an oral dose, bioavailability will be less than 1 (depending upon absorption, first pass metabolism etc.), requiring a larger loading dose.
The infusion rate needed to achieve the 35mg/L concentration can be determined as follows...