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Old 03-28-2013
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Question pharmacokinetics:

57 years male in ICU because of ARDS diagnosed with pseudomonas aeruginosa infection. treatment with cftazidine + gentamicin started. gentamicin t 1/2 = 3 hrs in this patient then what % of initial dose drug wil remain in his body 6hrs later??

a) 12.5
b) 25
c)50
d) 75
e)37.5
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Old 03-28-2013
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Quote:
Originally Posted by neha_subh View Post
57 years male in ICU because of ARDS diagnosed with pseudomonas aeruginosa infection. treatment with cftazidine + gentamicin started. gentamicin t 1/2 = 3 hrs in this patient then what % of initial dose drug wil remain in his body 6hrs later??

a) 12.5
b) 25
c)50
d) 75
e)37.5
I think 25%
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Old 03-28-2013
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Its goinna be 25%
Explanation: Beause ceftazidime doesn't affect the pharmacokinetics of gentamicin in any way, almost no known effect on P450 , further gentamycin donot bind to any protien or strored so no chances of displacement and altered kinetics. Rest is plane explanation , a druge with a half life of 3 hourswould remain 50% of its plasma concentration, likewise after 6 hours of the administration it would be reduced to 1/4th of the original i.e 25%.
However this combination is synergistic in itself i.e more or potentiated effect than the plain sum of their individual effects.Just like 2+2= 5

Last edited by dr_ali_khan; 03-28-2013 at 07:46 AM. Reason: further detail
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Old 03-29-2013
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Default corect answer:B)

57 years male in ICU because of ARDS diagnosed with pseudomonas aeruginosa infection. treatment with cftazidine + gentamicin started. gentamicin t 1/2 = 3 hrs in this patient then what % of initial dose drug wil remain in his body 6hrs later??

b) 25


corect answer is B)

Explanation:

for any given First order elimination processes, 50% of initial amount eliminated at 1st t 1/2 life, 50% remaining amount of drug eliminated at 2nd half life, and so on..therefore:

after 3 hrs ---50% drug remains in the body--eg: from 100--50% remains
after another 3 hrs (at 6hr)---another 50% of remaining 50% wil be eliminated--eg: from 50%---25% remains
or we can say after 6hrs, 75% drug eliminated and 25% of initial dose of drug remains in the body.
hence after 6hrs of initial dose 25% of drug remains in the body.
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