How to build a differential equation of quantity by time of a drug that is in the digestive system and...











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I'm giving that a child has swallowed 11 pills of 100 milligrams of a drug and was rushed into the emergency room after 2 hours by that time the drugs have passed from his stomach to his intestines.



The drug is absorbed in the blood steam at a proportional rate to the quantity in the digestive system,and the drug is removed from the blood at a proportional rate to the quantity that is in the blood.



(**)
It is known there is half-life for 5-hour blood absorption and half-life for removal from the blood (The time when the amount of the drug decreases by half in the blood,assuming there is no any drug absorbtion) is 6 Hours.



I'm trying to write a differential equation for the quantity of the drug in the digestive system and an equation of the quantity of the drug in the blood both equations are by time and with a starting condition.



I'm having trouble understanding (**) to write my first equation ,i'm trying to understand by how much time the quantity of the drug gets absorbed by the digestive system and delivered to the bloodstream to build my first equation.
From the given i can say that



G(0)=1,100 (the quantity of the drug in the digestive system at the initial time is 1,100 milligrams)










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    up vote
    2
    down vote

    favorite












    I'm giving that a child has swallowed 11 pills of 100 milligrams of a drug and was rushed into the emergency room after 2 hours by that time the drugs have passed from his stomach to his intestines.



    The drug is absorbed in the blood steam at a proportional rate to the quantity in the digestive system,and the drug is removed from the blood at a proportional rate to the quantity that is in the blood.



    (**)
    It is known there is half-life for 5-hour blood absorption and half-life for removal from the blood (The time when the amount of the drug decreases by half in the blood,assuming there is no any drug absorbtion) is 6 Hours.



    I'm trying to write a differential equation for the quantity of the drug in the digestive system and an equation of the quantity of the drug in the blood both equations are by time and with a starting condition.



    I'm having trouble understanding (**) to write my first equation ,i'm trying to understand by how much time the quantity of the drug gets absorbed by the digestive system and delivered to the bloodstream to build my first equation.
    From the given i can say that



    G(0)=1,100 (the quantity of the drug in the digestive system at the initial time is 1,100 milligrams)










    share|cite|improve this question
























      up vote
      2
      down vote

      favorite









      up vote
      2
      down vote

      favorite











      I'm giving that a child has swallowed 11 pills of 100 milligrams of a drug and was rushed into the emergency room after 2 hours by that time the drugs have passed from his stomach to his intestines.



      The drug is absorbed in the blood steam at a proportional rate to the quantity in the digestive system,and the drug is removed from the blood at a proportional rate to the quantity that is in the blood.



      (**)
      It is known there is half-life for 5-hour blood absorption and half-life for removal from the blood (The time when the amount of the drug decreases by half in the blood,assuming there is no any drug absorbtion) is 6 Hours.



      I'm trying to write a differential equation for the quantity of the drug in the digestive system and an equation of the quantity of the drug in the blood both equations are by time and with a starting condition.



      I'm having trouble understanding (**) to write my first equation ,i'm trying to understand by how much time the quantity of the drug gets absorbed by the digestive system and delivered to the bloodstream to build my first equation.
      From the given i can say that



      G(0)=1,100 (the quantity of the drug in the digestive system at the initial time is 1,100 milligrams)










      share|cite|improve this question













      I'm giving that a child has swallowed 11 pills of 100 milligrams of a drug and was rushed into the emergency room after 2 hours by that time the drugs have passed from his stomach to his intestines.



      The drug is absorbed in the blood steam at a proportional rate to the quantity in the digestive system,and the drug is removed from the blood at a proportional rate to the quantity that is in the blood.



      (**)
      It is known there is half-life for 5-hour blood absorption and half-life for removal from the blood (The time when the amount of the drug decreases by half in the blood,assuming there is no any drug absorbtion) is 6 Hours.



      I'm trying to write a differential equation for the quantity of the drug in the digestive system and an equation of the quantity of the drug in the blood both equations are by time and with a starting condition.



      I'm having trouble understanding (**) to write my first equation ,i'm trying to understand by how much time the quantity of the drug gets absorbed by the digestive system and delivered to the bloodstream to build my first equation.
      From the given i can say that



      G(0)=1,100 (the quantity of the drug in the digestive system at the initial time is 1,100 milligrams)







      calculus differential-equations






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      asked Dec 1 at 13:25









      user3133165

      1758




      1758






















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          You get as equations
          begin{align}
          dot G &= -k_1G\
          dot L &= k_1G-k_2L
          end{align}

          and from the half-life times $e^{-5k_1}=0.5$ and $e^{-6k_2}=0.5$, where time is measured in hours.






          share|cite|improve this answer





















          • So the first equation is quantity of the drug in the digestive system, and the second one is the quantity that is in the bloodstream?
            – user3133165
            Dec 1 at 13:37










          • Could you please let me understand the $e^{-5k_{1}}=0.5 $ and $e^{-6k_{2}}=0.5$ this is the part that is giving me a hard time understanding
            – user3133165
            Dec 1 at 13:39












          • Yes. I interpreted the naming convention to take the second consonant of "digestive" and "blood", you might want to take more conventional variable names, if such a convention exists.
            – LutzL
            Dec 1 at 13:39






          • 1




            The solution is $G(t)=e^{-k_1t}G(0)$. For $G(t)=0.5G(0)$ you need thus $e^{-k_1t}=0.5$. $t=5$ is given, which allows to compute $k_1$.
            – LutzL
            Dec 1 at 13:41










          • I'm trying to solve the first equation by separating and then integrating is this correct?
            – user3133165
            Dec 1 at 13:50











          Your Answer





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          1 Answer
          1






          active

          oldest

          votes








          1 Answer
          1






          active

          oldest

          votes









          active

          oldest

          votes






          active

          oldest

          votes








          up vote
          1
          down vote



          accepted










          You get as equations
          begin{align}
          dot G &= -k_1G\
          dot L &= k_1G-k_2L
          end{align}

          and from the half-life times $e^{-5k_1}=0.5$ and $e^{-6k_2}=0.5$, where time is measured in hours.






          share|cite|improve this answer





















          • So the first equation is quantity of the drug in the digestive system, and the second one is the quantity that is in the bloodstream?
            – user3133165
            Dec 1 at 13:37










          • Could you please let me understand the $e^{-5k_{1}}=0.5 $ and $e^{-6k_{2}}=0.5$ this is the part that is giving me a hard time understanding
            – user3133165
            Dec 1 at 13:39












          • Yes. I interpreted the naming convention to take the second consonant of "digestive" and "blood", you might want to take more conventional variable names, if such a convention exists.
            – LutzL
            Dec 1 at 13:39






          • 1




            The solution is $G(t)=e^{-k_1t}G(0)$. For $G(t)=0.5G(0)$ you need thus $e^{-k_1t}=0.5$. $t=5$ is given, which allows to compute $k_1$.
            – LutzL
            Dec 1 at 13:41










          • I'm trying to solve the first equation by separating and then integrating is this correct?
            – user3133165
            Dec 1 at 13:50















          up vote
          1
          down vote



          accepted










          You get as equations
          begin{align}
          dot G &= -k_1G\
          dot L &= k_1G-k_2L
          end{align}

          and from the half-life times $e^{-5k_1}=0.5$ and $e^{-6k_2}=0.5$, where time is measured in hours.






          share|cite|improve this answer





















          • So the first equation is quantity of the drug in the digestive system, and the second one is the quantity that is in the bloodstream?
            – user3133165
            Dec 1 at 13:37










          • Could you please let me understand the $e^{-5k_{1}}=0.5 $ and $e^{-6k_{2}}=0.5$ this is the part that is giving me a hard time understanding
            – user3133165
            Dec 1 at 13:39












          • Yes. I interpreted the naming convention to take the second consonant of "digestive" and "blood", you might want to take more conventional variable names, if such a convention exists.
            – LutzL
            Dec 1 at 13:39






          • 1




            The solution is $G(t)=e^{-k_1t}G(0)$. For $G(t)=0.5G(0)$ you need thus $e^{-k_1t}=0.5$. $t=5$ is given, which allows to compute $k_1$.
            – LutzL
            Dec 1 at 13:41










          • I'm trying to solve the first equation by separating and then integrating is this correct?
            – user3133165
            Dec 1 at 13:50













          up vote
          1
          down vote



          accepted







          up vote
          1
          down vote



          accepted






          You get as equations
          begin{align}
          dot G &= -k_1G\
          dot L &= k_1G-k_2L
          end{align}

          and from the half-life times $e^{-5k_1}=0.5$ and $e^{-6k_2}=0.5$, where time is measured in hours.






          share|cite|improve this answer












          You get as equations
          begin{align}
          dot G &= -k_1G\
          dot L &= k_1G-k_2L
          end{align}

          and from the half-life times $e^{-5k_1}=0.5$ and $e^{-6k_2}=0.5$, where time is measured in hours.







          share|cite|improve this answer












          share|cite|improve this answer



          share|cite|improve this answer










          answered Dec 1 at 13:32









          LutzL

          54.3k41953




          54.3k41953












          • So the first equation is quantity of the drug in the digestive system, and the second one is the quantity that is in the bloodstream?
            – user3133165
            Dec 1 at 13:37










          • Could you please let me understand the $e^{-5k_{1}}=0.5 $ and $e^{-6k_{2}}=0.5$ this is the part that is giving me a hard time understanding
            – user3133165
            Dec 1 at 13:39












          • Yes. I interpreted the naming convention to take the second consonant of "digestive" and "blood", you might want to take more conventional variable names, if such a convention exists.
            – LutzL
            Dec 1 at 13:39






          • 1




            The solution is $G(t)=e^{-k_1t}G(0)$. For $G(t)=0.5G(0)$ you need thus $e^{-k_1t}=0.5$. $t=5$ is given, which allows to compute $k_1$.
            – LutzL
            Dec 1 at 13:41










          • I'm trying to solve the first equation by separating and then integrating is this correct?
            – user3133165
            Dec 1 at 13:50


















          • So the first equation is quantity of the drug in the digestive system, and the second one is the quantity that is in the bloodstream?
            – user3133165
            Dec 1 at 13:37










          • Could you please let me understand the $e^{-5k_{1}}=0.5 $ and $e^{-6k_{2}}=0.5$ this is the part that is giving me a hard time understanding
            – user3133165
            Dec 1 at 13:39












          • Yes. I interpreted the naming convention to take the second consonant of "digestive" and "blood", you might want to take more conventional variable names, if such a convention exists.
            – LutzL
            Dec 1 at 13:39






          • 1




            The solution is $G(t)=e^{-k_1t}G(0)$. For $G(t)=0.5G(0)$ you need thus $e^{-k_1t}=0.5$. $t=5$ is given, which allows to compute $k_1$.
            – LutzL
            Dec 1 at 13:41










          • I'm trying to solve the first equation by separating and then integrating is this correct?
            – user3133165
            Dec 1 at 13:50
















          So the first equation is quantity of the drug in the digestive system, and the second one is the quantity that is in the bloodstream?
          – user3133165
          Dec 1 at 13:37




          So the first equation is quantity of the drug in the digestive system, and the second one is the quantity that is in the bloodstream?
          – user3133165
          Dec 1 at 13:37












          Could you please let me understand the $e^{-5k_{1}}=0.5 $ and $e^{-6k_{2}}=0.5$ this is the part that is giving me a hard time understanding
          – user3133165
          Dec 1 at 13:39






          Could you please let me understand the $e^{-5k_{1}}=0.5 $ and $e^{-6k_{2}}=0.5$ this is the part that is giving me a hard time understanding
          – user3133165
          Dec 1 at 13:39














          Yes. I interpreted the naming convention to take the second consonant of "digestive" and "blood", you might want to take more conventional variable names, if such a convention exists.
          – LutzL
          Dec 1 at 13:39




          Yes. I interpreted the naming convention to take the second consonant of "digestive" and "blood", you might want to take more conventional variable names, if such a convention exists.
          – LutzL
          Dec 1 at 13:39




          1




          1




          The solution is $G(t)=e^{-k_1t}G(0)$. For $G(t)=0.5G(0)$ you need thus $e^{-k_1t}=0.5$. $t=5$ is given, which allows to compute $k_1$.
          – LutzL
          Dec 1 at 13:41




          The solution is $G(t)=e^{-k_1t}G(0)$. For $G(t)=0.5G(0)$ you need thus $e^{-k_1t}=0.5$. $t=5$ is given, which allows to compute $k_1$.
          – LutzL
          Dec 1 at 13:41












          I'm trying to solve the first equation by separating and then integrating is this correct?
          – user3133165
          Dec 1 at 13:50




          I'm trying to solve the first equation by separating and then integrating is this correct?
          – user3133165
          Dec 1 at 13:50


















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