{"id":80527,"date":"2018-02-20T23:50:30","date_gmt":"2018-02-20T23:50:30","guid":{"rendered":"https:\/\/writemyessayfree.com\/pharmacokinetics-problems"},"modified":"2017-08-18T07:41:36","modified_gmt":"2017-08-18T07:41:36","slug":"pharmacokinetics-problems","status":"publish","type":"post","link":"https:\/\/www.benedictsol.com\/blogs\/pharmacokinetics-problems\/","title":{"rendered":"PHARMACOKINETICS PROBLEMS"},"content":{"rendered":"<ol>\n<li>Assuming first order kinetics what fraction of an IV drug dose remains in the body after 4 half-lives?<\/li>\n<li>The t<sub>1\/2<\/sub> of a drug is 6 hours. What fraction is left in the body at 21h post drug administration?<\/li>\n<li>Twenty percent of a drug dose remains in the body at t=10hours. What is the half-life of the drug?<\/li>\n<li>The plasma concentration of a drug administered by IV bolus injection may be described by the following equation:<\/li>\n<\/ol>\n<p>C<sub>t <\/sub>= 0.92e <sup>-0.35t<\/sup><\/p>\n<p>where C<sub>t<\/sub> is in units of mg\/L and the time (t) is in hours.<\/p>\n<p>If the dose is 50mg calculate the following:<\/p>\n<ul>\n<li>The plasma concentration at 6.5h post dosing.<\/li>\n<li>The plasma half-life.<\/li>\n<li>The volume of distribution.<\/li>\n<li>The area under the plasma concentration versus time curve.<\/li>\n<li>The total clearance.<\/li>\n<\/ul>\n<p>&nbsp;<\/p>\n<ol start=\"5\">\n<li>Drug X is administered as an IV bolus dose of 100mg and the following plasma concentrations were obtained with time:<\/li>\n<\/ol>\n<table>\n<tbody>\n<tr>\n<td width=\"107\">Time (h)<\/td>\n<td width=\"73\">0.25<\/td>\n<td width=\"72\">0.5<\/td>\n<td width=\"72\">1.0<\/td>\n<td width=\"72\">3.0<\/td>\n<td width=\"73\">5.0<\/td>\n<td width=\"73\">7.0<\/td>\n<td width=\"73\">10.0<\/td>\n<\/tr>\n<tr>\n<td width=\"107\">Plasma Concentration (mg\/L)<\/td>\n<td width=\"73\">2.6<\/td>\n<td width=\"72\">2.4<\/td>\n<td width=\"72\">2.1<\/td>\n<td width=\"72\">1.2<\/td>\n<td width=\"73\">0.75<\/td>\n<td width=\"73\">0.45<\/td>\n<td width=\"73\">0.2<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p>Calculate the volume of distribution, plasma half-life and clearance of X.<\/p>\n<p>X was subsequently administered via the oral route at a dose of 200mg as both an aqueous solution and as a formulated product. The measured areas under the plasma concentration time curves were 14.3 mg\/L.h and 12.6 mg\/L.h for the solution dose and formulated product respectively.<\/p>\n<p>&nbsp;<\/p>\n<p>Using this data calculate the relative and absolute bioavailability of X.<\/p>\n<ol start=\"6\">\n<li>Drug W on IV administration to an experimental animal at a dose of 10mg\/kg (animal weight 2.3kg) gave the following plasma concentrations with time:<\/li>\n<\/ol>\n<table width=\"690\">\n<tbody>\n<tr>\n<td width=\"104\">Time (h)<\/td>\n<td width=\"57\">0.1<\/td>\n<td width=\"66\">0.25<\/td>\n<td width=\"66\">0.5<\/td>\n<td width=\"66\">0.75<\/td>\n<td width=\"67\">1.0<\/td>\n<td width=\"65\">1,5<\/td>\n<td width=\"66\">2.0<\/td>\n<td width=\"66\">3.0<\/td>\n<td width=\"66\">4.0<\/td>\n<\/tr>\n<tr>\n<td width=\"104\">Plasma Concentration<\/p>\n<p>(mg\/L)<\/p>\n<\/td>\n<td width=\"57\">4.2<\/td>\n<td width=\"66\">3.2<\/td>\n<td width=\"66\">2.3<\/td>\n<td width=\"66\">1.8<\/td>\n<td width=\"67\">1.5<\/td>\n<td width=\"65\">1.2<\/td>\n<td width=\"66\">1.09<\/td>\n<td width=\"66\">0.88<\/td>\n<td width=\"66\">0.71<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p>&nbsp;<\/p>\n<p>Using the above data:<\/p>\n<ul>\n<li>Draw a diagram of a compartmental model that describes the plasma disposition of the drug and indicate any relevant rate constants.<\/li>\n<li>Write an equation describing the plasma concentration versus time curve (use numbers rather than symbols as much as possible).<\/li>\n<li>Calculate the values of the rate constants you have indicated in part (a).<\/li>\n<li>What is the terminal half-life of drug W?<\/li>\n<li>What is the volume of distribution of W and what is the initial dilution volume (volume of the central compartment)?<\/li>\n<li>Calculate the area under the plasma concentration versus time curve and compare this value with that obtained using the trapezoidal method.<\/li>\n<\/ul>\n<p>&nbsp;<\/p>\n<ol start=\"7\">\n<li>Drug Y is administered orally to a patient at a dose of 100mg and the following plasma concentrations were obtained with time:<\/li>\n<\/ol>\n<table>\n<tbody>\n<tr>\n<td width=\"92\">Time (h)<\/td>\n<td width=\"59\">0.2<\/td>\n<td width=\"59\">0.4<\/td>\n<td width=\"59\">1.0<\/td>\n<td width=\"59\">2.0<\/td>\n<td width=\"59\">3.0<\/td>\n<td width=\"59\">4.0<\/td>\n<td width=\"59\">6.0<\/td>\n<td width=\"59\">8.0<\/td>\n<td width=\"55\">10.0<\/td>\n<\/tr>\n<tr>\n<td width=\"92\">&nbsp;<\/td>\n<td width=\"59\">&nbsp;<\/td>\n<td width=\"59\">&nbsp;<\/td>\n<td width=\"59\">&nbsp;<\/td>\n<td width=\"59\">&nbsp;<\/td>\n<td width=\"59\">&nbsp;<\/td>\n<td width=\"59\">&nbsp;<\/td>\n<td width=\"59\">&nbsp;<\/td>\n<td width=\"59\">&nbsp;<\/td>\n<td width=\"55\">&nbsp;<\/td>\n<\/tr>\n<tr>\n<td width=\"92\">Plasma Concentration (mg\/L)<\/td>\n<td width=\"59\">0.33<\/td>\n<td width=\"59\">1.0<\/td>\n<td width=\"59\">1.8<\/td>\n<td width=\"59\">2.02<\/td>\n<td width=\"59\">2.0<\/td>\n<td width=\"59\">1.6<\/td>\n<td width=\"59\">1.0<\/td>\n<td width=\"59\">0.6<\/td>\n<td width=\"55\">0.38<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p>&nbsp;<\/p>\n<p>Calculate the absorption and elimination rate constants, the volume of distribution and clearance of Y assuming that F, the bioavailability, is equal to 0.75.<\/p>\n<p>If the 100mg oral dose is repeated at 8 hourly intervals calculate the maximum, minimum and average steady-state plasma concentrations.<\/p>\n<ol start=\"8\">\n<li>Drug A is administered IV to a patient according to the following table:<\/li>\n<\/ol>\n<p>&nbsp;<\/p>\n<table>\n<tbody>\n<tr>\n<td width=\"59\">Day<\/td>\n<td width=\"85\">Time<\/td>\n<td width=\"85\">Dose (mg)<\/td>\n<\/tr>\n<tr>\n<td width=\"59\">1<\/td>\n<td width=\"85\">4.00pm<\/td>\n<td width=\"85\">80<\/td>\n<\/tr>\n<tr>\n<td width=\"59\">&nbsp;<\/td>\n<td width=\"85\">11.00pm<\/td>\n<td width=\"85\">160<\/td>\n<\/tr>\n<tr>\n<td width=\"59\">2<\/td>\n<td width=\"85\">7.00am<\/td>\n<td width=\"85\">120<\/td>\n<\/tr>\n<tr>\n<td width=\"59\">&nbsp;<\/td>\n<td width=\"85\">1.30pm<\/td>\n<td width=\"85\">80<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p>&nbsp;<\/p>\n<p>At 4.00pm on day 2 a plasma sample was analysed for A and a concentration of 6mg\/L was obtained.<\/p>\n<p>Is this measured concentration consistent with the expected value?<\/p>\n<p>Volume of distribution of A is 14.5L and clearance is 40mL\/min.<\/p>\n<p><strong>&nbsp;<\/strong><\/p>\n","protected":false},"excerpt":{"rendered":"<p>Assuming first order kinetics what fraction of an IV drug dose remains in the body after 4 half-lives? The t1\/2 of a drug is 6 hours. What fraction is left in the body at 21h post drug administration? Twenty percent <a href=\"https:\/\/www.benedictsol.com\/blogs\/pharmacokinetics-problems\/\" class=\"read-more\">Read More &#8230;<\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[],"tags":[],"class_list":["post-80527","post","type-post","status-publish","format-standard","hentry"],"_links":{"self":[{"href":"https:\/\/www.benedictsol.com\/blogs\/wp-json\/wp\/v2\/posts\/80527","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.benedictsol.com\/blogs\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.benedictsol.com\/blogs\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.benedictsol.com\/blogs\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.benedictsol.com\/blogs\/wp-json\/wp\/v2\/comments?post=80527"}],"version-history":[{"count":0,"href":"https:\/\/www.benedictsol.com\/blogs\/wp-json\/wp\/v2\/posts\/80527\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.benedictsol.com\/blogs\/wp-json\/wp\/v2\/media?parent=80527"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.benedictsol.com\/blogs\/wp-json\/wp\/v2\/categories?post=80527"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.benedictsol.com\/blogs\/wp-json\/wp\/v2\/tags?post=80527"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}