new_dream77
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pt with an arrythmia is to receive lidocaine by constant I.V infusion,the target plasma conc. is 3mg/ml.the pharmacokinetic parametrs of lidocaine are Vd 70l, CL 35l/hr, t1/2 1.4 hrs. an infusion is begun. plasma conc.of lidocaine is measured 2.8 hrs later and reported to b 1.5 mg/ml.this indicates tht final steady state plasma conc in this pt will be??
A> 1.5mg/l
B> 2.0mg/l
C > 3.0mg/l
D>6.0mg/l
E>insufficient data to answer
PLZ EXPLAIN UR ANS
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| new_dream77
Forum Newbie
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ok guys this q is from katzung,
ans given is 2.0mg/l ,
i cudnt understan how ?
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| ssrpk
Forum Fanatic
Topics: 154
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Vd CL are distractiors in this q
consider t1/2 only which is 1.4 hrs
now:
1st t1/2- 50%
2nd t1/2- 75%
3rd t1/2 87.5% and so on so forth!
so foloowing 2 half lives[2.8 hrs] after infusion 75% of steady state conc. will be acheived irrespctive of the dose [here in q- 1.5mg/ml]
therefore 1.5/0.75 = 2.0 mg/ml [100% of Css]
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life is guud
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| new_dream77
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thanks ssrpk
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| 99doc
Forum Elite
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The book explains the answer in a tough way.
But ssrpk u have done a great job.
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