Case #2

A 30 year old female patient comes to your retail pharmacy topick up a prescription for Tylenol #3 (acetaminophen + codeine) forpain control. You enter the prescription into the computer systemand the computer’s interaction checker flags an interaction betweenTylenol #3 and the patient’s fluoxetine prescription. Answerquestions 1-3 regarding this case.

. What would you expect to see if you give codeine to:a) a poor metabolizer for the enzym CYP2D6 and b)an ultra-rapid metabolizer of the enzymeCYP2D6.

Case #3

C.G., A 29 year-old female (yof) patient, presents for inpatientcare. You are working as a staff pharmacist in the hospitalpharmacy and are asked to verify/fill her prescriptions. Hercurrent medications are for rifampin, nifedipine, amitriptyline,and fluoxetine, valproate sodium, and lamotrigine. Please identifyat least three potential biotransformation-related druginteractions in the scenario above and describe the potentialmechanism for the interaction. Describe the expected effect (i.e.,increased/decreased parent drug concentration, increased/decreasedmetabolite concentration).

Interaction #1 & effect on plasmaconcentrations –

Interaction #2 & effect on plasmaconcentrations –

Interaction #3 & effect on plasma concentrations-

A week later, C.G. is still in the hospital. She is veryhypertensive and the physician elects to start IV propranolol 2 mg.Is this an appropriate dose of propranolol for hypertensionmanagement when the patient goes home? If not, why not?

In addition to her hypertension, C.G. developed an arrhythmia.The physician ordered lidocaine to be given IV. Initially, thisdrug produced a therapeutic plasma concentration (Css total of 4mg/L). This drug has a high extraction ratio and is highly bound toalpha-1-acid glycoprotein. A few days after starting the drug, thetotal plasma concentration remained the same, but the free drugconcentration was found to be increased.

What is a potential explanation for this change in freedrug concentration?

Why would total concentration stay the same? Whatfactors would alter the total drug concentration(Css) of lidocaine?