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Pceut532_Exam3_2008 Key - PHARMACEUTICS 532 Winter 2008...

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Unformatted text preview: PHARMACEUTICS 532 Winter 2008 Midterm #3 February 29th Name K 6 ‘1 Student # I Questions Points (30303040 15 10 21 ©P°N95919>P°N9 A p . U‘l Toial 100 Page 2 of 9 1) (9 pts) Answer the following questions true or false a. As plasma concentrations increase and approach the Km of the drug’s major clearance pathway, a change in the dose produces more than a proportional change in the plasma AUC. TRUE_X_ FALSE b. The rate of decline of effect with time is dependent on the elimination rate constant (K) and the slope of the effect-Log concentration curve. TRUE_X_ FALSE 0. For a drug demonstrating Michaelis-Menten pharmacokinetics, the clearance of the drug is independent of the plasma drug concentration when it is much below the Km. TRUE_X_ FALSE 2) (10 pts) A patient who was given phenytoin at 300 mg/d had a phenytoin plasma concentration of 10.5 mg/L. The same patient was given phenytoin at 350 mg/d that resulted in a plasma phenytoin concentration of 13.5 mg/L. Using the Ludden method, determine the Vmax and Km for this subject and the dosing rate necessary to achieve a plasma phenytoin concentration of 17mg/L. DR/Css DR 300m Ida I105 m IL=28.57 l 300m Ida 350 m Iday/13.5 mg/L=25.93 350m Ida ‘ Slope: (350—300)/(25.93-28.57)=-18.9 Km=18.9 mglL Vmax =DR+££KM e300mg/day+W*18.9=84omg/day Coo 10.5mg/L V 840mg/day DR: max =————=398 Id 2400 Id K 18.9mg/L mg ay mg ay 1+1 1+———— C°° 17mg/L 3) (6pts) Provide a definition for the following parameters: a. Emax: __The maximum effect/response b. EC5O:__ The concentration of drug that produces half—maximal effect/response __ Page 3 of 9 4) (6 pts) In the space next to the plots below, identify which parameter is different between the two curves, and indicate how it differs (example: Emax of A >B). 125 100 75 Effect 50 25 D 25 50 75 100 125 150 175 200 Concentration 250 200 150 Effect 100 50 -; 0 25 50 75 100 125 150 175 200 Concentration Emax B>A 125 100 7S Effe cl: 50 25 0 25 50 75 100 125 150 175 200 Concentration ECso B>A Page 4 of 9 5) (6 pts) For a drug demonstrating one compartment behavior, indicate the regions where the effect vs. time curve has the following characterisitcs: a. Essentially flat (does not change much with time): Region 3 b. Declines linearly with time: Region 2 c. Declines exponentially with time: Region 1 120 100 Region 3 80 60 Effect 40 2.0 Region 1.”. 0.1 1. 10 100 1000 Concentration 6) (3 pts) The duration of effect is increased by _2XT1,2_ when the dose is increased fourfold. Page 5 of 9 7) (15 pts total) BL is a 50 year old female who has been receiving propranolol 40 mg/day for the last‘5 years. Fluoxetine has .now been prescribed. Fluoxetine is a known inhibitor of CYP2019 and CYP2D6. a. (12 pts) Given the following metabolic scheme and the percent of dose accounted for by each metabolite, calculate the maximum increase in steady state propranolol concentrations that BL could have when fluoxetine is added. Not CYP or UGT ———-————-——> Propranolol other unknown (10%) CYP2C19 CYP2D6 ‘ NLA Propranolol 4—OH—Propranolol (5 %) (25%) Glucuronide (20%) Wt ST UGT 05996 5 0.35 °l9 W” 0 cl Cl 09": 0.05 4.05) r02 :: OJ-ts’ vL “WOH—sulfate. 4—OH—g1ucuronide l (20%) (20%) T H741 {Mn west 2 O.Q$*o.‘l§e 6.70 U I 9 l—— (3.7 = 03 Cl “mm“mfi V. 1 N a 53/0/12 mlnbl‘ml a ,_ F‘D!’E UhW‘W C55 -"‘"'"’ $5 «J (9 3 eCJ b. ( 3 pts) If BL is a poor metabolizer of CYP2D6, would the percent increase in WE concentrations of propranolol caused by fluoxetine be GREATER, ESSE R THE SAME compared to someone who is an extensive metabolizer of D6? ' Page 6 of9 8) (10 pts) There is an increase incidence of peripheral neuropathy associated with the use of isoniazid in slow acetylator unless dosage adjustment is made. Explain, ’using equations, why targeting a therapeutic serum concentration in all patients if an assay was available could reduce the incidence of toxicity in slow acetylators to levels comparable to the incidence found in fast acetylators lsoniazid C NAT (UNC— t? 2 Cir (“MEG K.) Acetyllsoniazid Hydrazone Metabolite ---—? COW Cl NM9 7 to Jim manager» then slow alt-2,4360% Wm ' M' tc “m 5 ‘0‘») MM «i! Cl {awe 'h Will“ It? ream. t PM“: Cw T F” “‘67.... 3, Cl J’ D l re 09“” {a ‘b C Dem Jr W l” P —- am: 059 a L; KW 1033 Ct ”17‘ Com calw 74L 9) Fill in the Blank: (3 pts each/21 total) Wflflm a. Codeine will not be an effective analgesic in poor metabolizers of (59300 J’ W b. 5“ L.) 09:93le and PA enftol- N are two drugs that are predominately metabolized by CYPZCQ. c. CK and ST are two patients who are treated with the same dose of the proton pump inhibitor, omeprazole, for gastroesophagel reflux disease (GERD). CK is of Asian ethnic background and ST is of Caucasian ethnic background. Which patient has the highest probability of being successfully treated with the omeprazole. CK . d. The incidence of slow acetylators of N—acetyltransferase is approximate/lg! . [O 290 “Z? in the Asian population compared to 559 in the Caucasian and African—American populations. 5 ANolgfiouO, Caué/wucolm/ 4h! 0 GLIQ e. A“+‘&Fm°‘*’5 is a major therapeutic drug class thatfllude several drugs predominantly metabolized by CYP2D6. Page 7 of9 10) (5 pts) Using the following group of patients, fill in the bar—graph to describe the concept of gene-dosing for a CYP2D6 substrate. Group 1: CYP2D6*1/*1 Wild type Group 2: CYP2D6*10/*1O Homozygous for intermediate activity allele Group 3: CYP2D6*10/*1 Heterozygous for intermediate activity allele Group 4: CYP2D6*4/*4: Poor metabolizers Group 5: CYP2D6*2/*2 (13 copies): ' Ultrametabolizer Concentration Dose Group 1 Group 2 Group 3 Group 4 Group 5 11) Fill in the Blank or circle best answer: (3 pts each/9 total) a. For high extraction ratio drugs. protein binding effects are only important for those that are highly protein bound, narrow therapeutic index and are administered by which route? 0 on— 0 "GA b. For low extraction ratio drugs that are highly protein bound, When albumin concentrations decrease, usino total concentrations for therapeutic drug monitoring will (reflect or overestimate) unbound or active concentrations. 0. Given a drug with a free fr predict that the infant ' concentrations after bre 'on of 30% that the mother is receiving, would you - mr would not) have measurable serum —eeding Page 8 of9 ...
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