Study with the several resources on Docsity
Earn points by helping other students or get them with a premium plan
Prepare for your exams
Study with the several resources on Docsity
Earn points to download
Earn points by helping other students or get them with a premium plan
Various pharmacokinetic calculations for different drugs, including phenobarbital, MTX, gentamicin, and phenytoin. The calculations involve determining loading doses, maintenance doses, predicted concentrations, and adjusting doses based on serum albumin concentrations and creatinine clearance.
Typology: Exams
1 / 20
This page cannot be seen from the preview
Don't miss anything!
Spring 2008 Final Exam (Version A)_Answers
On my honor, I have neither given nor received unauthorized aid in doing this assignment.
Print: Sign:
Name
Total points for exam 100 points (16 questions)
Question #1: (5 points) What is the general reason that the ultimate desired maintenance dose of Carbamazepine is much higher than the beginning dose?
A) Pharmacodynamic drug tolerance B) Disease progression C) Metabolic enzyme autoinduction D) Renal function increased E) Carbamazepine is a high hepatic extraction drug
Question #3: (10 points) T.X. is a 53 kg female patient (47 years) to receive methotrexate therapy. Her serum creatinine is 1.2 mg/dL. She is treated with a loading dose (20 mg) followed by an infusion of 25 mg/h over 36 hours. She will then receive a 10 mg/m^2 dose of leucovorin q6h (four doses) followed by eight oral doses (q6h) of 20 mg. Calculate the expected MTX concentration at 48 hour after the start of the infusion and the expected time that the methotrexate level will fall below 0.1 μM by using the typical half-life parameters? After the drug sampling report [14 μM (24h), 0.40 μM (60 h), and 0.20 μM (75h)], adjust your prediction according to data. (You can assume the plasma concentration already reached steady state after 24 hrs infusion.).
A) Expected: C48h=0.75uM, t0.1uM=73 hr; Adjusted: C48h=1.74uM, t0.1uM=90 hr B) Expected: C48h=2.12uM, t0.1uM=85 hr; Adjusted: C48h=0.75uM, t0.1uM=90 hr C) Expected: C48h=0.75uM, t0.1uM=90 hr; Adjusted: C48h=0.82uM, t0.1uM=90 hr D) Expected: C48h=1.74uM, t0.1uM=80 hr; Adjusted: C48h=0.74uM, t0.1uM=108 hr E) Expected: C48h=0.55uM, t0.1uM=68 hr; Adjusted: C48h=1.74uM, t0.1uM=95 hr
Calculate the expected MTX steady-state concentration (in μM).
Calculate the predicted concentrations at 24, 48 and 60 h after the start of the MTX infusion. 36 h: 11.87 μM
The reported levels were 14 μM (24h), 0.40 μM (60 h), and 0.20 μM (75h)
1
Question #5: (5 points) D.H. is a male 71kg patient with methicillin-resistant S. aureus infection. Which of the following would be a recommended dosing regimen if a gentamicin plasma concentration of 5mg/L 8 hours after the start of the infusion was measured? Please assume average population PK parameters for D.H.
A) 500mgQ24h B) 500mgQ36h C) 500mgQ48h D) All of the above E) None of the above
Question #6: (5 points) A 65 year old male (75kg) is admitted to the ER with ventricular tachycardia. He is started on procainamide with a loading dose of 15 mg/kg over 1 hr and a maintenance dose of 120 mg/hr. Serum levels are measured at one hour and twenty-four hours. Concentrations are 6mg/L and 8mg/L. Upon release this patient is to be switched to oral procainamide. Calculate a dosing regimen to give a steady state average concentration of 6 mg/L. Assume the twenty-four hour concentration is at steady state. Hint: use the IV bolus equation for a loading dose to find the Vd. Please calculate ke as ke=Cl/Vd. Do not use any other method.
A) 850 mg BID B) 800 mg QD C) 700 mg TID D) 850 mg TID E) 700 mg BID
Cl=MDS/Cavess=120mg/hr1hr0.87 / 8mg/L=13.05 L/hr Vd=LD S/Cp0=15mg/kg75kg0.87/ 6mg=163.13L Ke=Cl/Vd=13.05 L/hr/163.13L ~ 0.08hr- Tau=ln(8/4)/0.08=8.66hr~8hr Dose=CavessCltau/(0.85*0.87)=847.1 ~ 850mg Dosing Regimen=850mg TID
Question #8: (5 points) F.W. is a 55-year-old, 75kg male with glomerular nephritis. His creatinine clearance is reasonably good, but he has a serum albumin concentration of 2.2g/dL. F.W. is receiving 350mg/day of phenytoin and has a steady-state phenytoin concentration of 7mg/L. What would be his phenytoin concentration be if his serum albumin concentration was normal? (Normal serum albumin=4.4g/dL).
A) 10.9 mg/L B) 12.7 mg/L C) 15.0 mg/L D) 20.0 mg/L E) 9 .0 mg/L
mg L g dL
g dL
mg L NormalAlbu
PatientsAlbu Cp (^) normal Cp 12. 7 / 1 0. (^142) .. 42 // 0. 1
7 / 1 ' minmin 0. 1
'
Question #9: (10 points) G.V., a 57-year-old, 55kg woman (5’4”) with congestive heart failure, was admitted to the hospital with for possible digoxin toxicity. Her serum creatinine was 2.8mg/dL, and her dosing regimen at home had been 0.25mg digoxin (tablets) daily for a year. Her digoxin plasma concentration on admission was 3.8μg/L. How long will it take for the digoxin concentration to fall from 3.8 to 2μg/L if no further doses are given?
A) 2.6 days B) 5.1 days C) 3.7 days D) 4.3 days E) 7.4 days IBW ( female ) 45. 5 2. 3 4 54. 7
85 2. 8 19.^18 min
( ) (^14057 )^55 mL dL
mg Cl (^) Cr female kg
day
L L day g
g Css Cl S F Dose 46. 05 1 3. 8
1 0. 7 250
V (^) d 3. (^8) kgL IBW 3. 1 ClCr 3. (^8) kgL 54. 7 kg 3. 1 19. (^18) min mL 267. 32 L
172 1
32
05 dayL day
L V k Cl e d
dayL days
gL
g
k
C
C t e 0. 172 3. 73
2
ln^3.^8 ln (^21)
1
Ritonavir inhibits P-gp in renal tubule, and Digoxin could be also eliminated by P-gp mediated renal tubular secretion as the renal clearance for digoxin decreases when Ritonavir is co- administered and Digoxin is a P-gp substrate. Base on the graph and table, it is clearly shown that Ritonavir could decrease Digoxin Total clearance, renal clearance, and increase volume of distribution, but Quinidine decreases the volume of distribution of Digoxin. Digoxin concentration could exceed its therapeutic window, resulting in toxicity when total clearance of Digoxin decreases.
Question #11: (5 points) Moxifloxacin is a new quinolone anti-infective agent. This class of antiinfective agents can complex with dietary minerals (calcium, iron, etc) and may cause reductions in bioavailability. The following data were obtained after IV bolus administration, oral administration, and oral administration with 100 mg iron (II) sulfate.
Which of the following statement is FALSE? A) Iron slows down the absorption rate of moxifloxacin as indicated by the change of the time to maximal concentration after the addition of iron (II) sulfate. B) Iron has effects on the absolute bioavailability of moxifloxacin. C) The oral bioavailability of moxifloxacin is relatively high (>95%). D) Co-administration of TUMS® (antacid, calcium carbonate) results in the increase of moxifloxcin exposure. E) The reason that bioavailability of an oral dosage form is less than 100% could be nurmerous, such as degradation, solubility/dissolution rate, and first-pass effect.
Question #13: (10 points) I.M. is a 50 year old male, 75 kg, 5’10”, intermittent asthmatic who presents to the emergency room with severe dyspnea, coughing, and wheezing. He is treated there with aerosol albuterol, but only partially clears. He is then given 400 mg of IV aminophylline (S = 0.8) over 30 minutes. Thirty minutes after the loading dose was administered ( minutes from time zero) the theophylline concentration was 14μg/ml. He has normal liver, kidney, and cardiac function and is afebrile. He is not receiving any other drugs. After the loading dose, M.P. was immediately started on an IV theophylline constant infusion of 55 mg/hr, Solu-Medrol IV and albuterol nebulization. Eight hours after the first serum level, a second level was 8μg/ml. Please calculate I.M.’s total body clearance, a second IV loading dose to increase his level from 8 μg/ml to 15 μg/ml, and a IV aminophylline infusion rate to maintain the concentration at 15 μg/ml.
A) Cl: 3.65L/h; LD: 185mg; MD: 150mg/h B) Cl: 2.99L/h; LD: 220mg; MD: 50mg/h C) Cl: 3.65L/h; LD: 185mg; MD: 70mg/h D) Cl: 6.56L/h; LD: 200mg; MD: 120mg/h E) Cl: 3.44L/h; LD: 200mg; MD: 80mg/h
L L
mg
mg C V Dose F S d (^) p 14 22.^86 400 1 0. 8
h
L h
L h
L
mgL h L L mg L
mgh
mg C C t t
V C C C C Cl R d
5 1. 56 6. 56
( 14 8 ) 8
2 22. 86 ( 14 8 ) ( 14 8 )
2 55 ( ) ( )
2 ( ) ( )
2 1 2 2 1
1 2 1 2
0
mg
mgL L S F LD Cp^ Vd 200
7 22. 86
h
h mg
mg S F MD Cpss^ Cl 123
Question #15: (5 points) In the following Mullen-plot of phenytoin, identify x1, y1 and x2.
A) x1=Vmax, y1=Km, x2=Css_ B) x1=Km, y1=Vmax, x2=Css_ C) x1=Vmax, y1= Css_3, x2=Km D) x1= Css_3, y1=km, x2=Vmax E) none of above
Question #16: (5 points)
Which combination of the following factors makes the serum creatinine level a good choice to estimate renal function?
E) All of the above
