Question

1. RM (65 kg) is a 78 years old-man with a heart condition. He is hospitalized and administered DRUG-A (F 0.02; fe 0.03; t24 hours; Vd 1.2 L/kg) as an iv-infusion. The effective plasma concentration for Drug A is 3 ug/mL a. Calculate the infusion rate necessary to maintain a steady state plasma concentration of 3 ug/mL. b Calculate how long it will take to reach 90% of steady state c. Calculate the loading dose. 2. After three days of Drug-A IV-infusion, RM complains of hand tremors and heat intolerance, typical side- effects of Drug-A. The Physician decides to switch RM to Drug-B (F0.60; fe0.6; t12 hours; Vd 2.1 L/kg). However, Drug-A must be completely eliminated from RM body before starting the new therapy with Drug-B because of severe interactions between the two drugs. a. How long it will take before they can start RM on Drug-B7 (e.g., 90% of Drug-A is eliminated) b. Calculate the infusion rate necessary to maintain a steady state plasma concentration of Drug-B at 2.5 ug/mL c Calculate how long it will take to reach 90% of steady state d. Calculate the loading dose for Drug-B 3. A blood sample taken at steady state has a plasma concentration of 3.5 μg/mL. What does it means? 4. RM is doing well on Drug-B. The Physician decides to send RM home and to switch him to oral dose. Drug- B is available as 200 mg tablets. a. How many 200 mg tablets of Drug-B RM must take per day to have the same therapeutic benefits (same exposure)? HINT: Calculate the IV-Dose (administered in one day)

Answer 1

1.i don't know what do you mean by Fe and F.

If,fe is clearance then

Infusion rate=clearance xsteady state plasma concentration

=0.03x(3/1000)=0.00009

[3 microgram=31000mg]

If,fe is not clearance

T1/2=0.693x(vd/clearance)

Clearance=(0.693xvd)/T1/2

=0.693x(1.2x1000)/4

=207.9

Infusion rate=clearance×steady state plasma concentration

=207.9(3/1000)

=0.6