Half-Life, Steady State, & Drug Interactions Case Analyses

Assignment Instructions

Read all three of the following cases and questions. Then, type your numbered responses to the questions in a document. Use complete sentences and support your answers with the textbook, and/or other scholarly sources. This should not be written in the format of an essay, but you must support your answers with the textbook and/or scholarly sources. This should be no more than 1-3 sentences. Format your in-text citations in APA-style and include an APA-style reference page in your document.

Case 1: Half-Life

JH is a 45 yo male who is currently on paroxetine (Paxil ) 40mg daily for depression. He has been on this med for about 6 months and has gained about 30lbs despite diet and a solid exercise routine. His Physician has attributed the weight gain to the paroxetine. He wishes to try fluoxetine (Prozac) to see if he can successfully treat his depression and lose weight.

How long would it take for the paroxetine to reach a level of about 2.5mg so you may safely start the fluoxetine regimen assuming the half life of paroxetine is 24hrs?

Case 2: Steady State

HT is a 26 yo female who has just started phenytoin (Dilantin) for her newly diagnosed seizure disorder. As she is just starting therapy, there is still a risk she may develop further seizures. How many days after starting the phenytoin would you expect her to be virtually free of that seizure risk?

Case 3: Drug Interaction

WR is a 67 yo male who has been placed on warfarin (Coumadin) for stroke prevention due to his atrial fibrillation. He has been on this medication about 3 months now and his last INR (international normalized ratio) was therapeutic via blood draw at 2.6 (goal INR 2-3).

He calls your clinic as he has recently started the antibiotic trimethoprim/sulfamethoxozole (Septra DS) 800mg twice daily for a sinus infection.

Are you concerned about a drug interaction at this time and if so, how is this drug interaction occurring? Also, do you expect to see a change in his INR level? Will it go up or down?

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