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 +2  (nbme22#9)

I thought this image was helpful.

https://doctorlib.info/physiology/medical/49.html





Subcomments ...

submitted by usmleuser007(112),

Someone care to explain why [time to steady-state concentration] is not the correct answer?

omerta  In pharmacokinetics, steady state refers to the situation where the overall intake of a drug is fairly in dynamic equilibrium with its elimination. In practice, it is generally considered that steady state is reached when a time of 4 to 5 times the half-life for a drug after regular dosing is started. The time to reach steady state is defined by the elimination half-life of the drug. So in a patient with renal dysfunction, the plasma half-life is going to be prolonged and the time to reach steady state will increase proportionally. +4  
belleng  loading dose is independent of the concentration of the drug in the plasma and the dose frequency...this is why you give a patient who is seizing a huge dose of anti-seizure meds in order to reach a theraputic range on the first dose despite the high risk of toxicity and side effects...primary objective when seizing is stoping the seizure so you want to increase the dose response curve with a massive load +  
belleng  loading dose is independent of DOSE (should have said dose, not concentration in plasma) & FREQUENCY +  


submitted by jooceman739(11),

Retinoblastoma:

The physician said the boy is unlikely to develop any other neoplasms, so he doesn't have the inherited Rb mutation.

In this case, he has the sporadic retinoblastoma. Sporadic retinoblastoma requires two somatic mutations of Rb in the same retinal cell.

Just as a side note: Inherited retinoblastomas tend to be bilateral. Sporadic are unilateral.

carls14  aren't retinal cells a type of somatic cell? Why not is the mutation not considered in the somatic cell of the child? +  
omerta  Although this mutation would be considered somatic, I believe the question is just asking you to be specific as to which cells. If you answered "somatic cells of the child," that's quite broad and could apply to almost anything. +3  
kernicterusthefrog  I had the same struggle and thought process. +  
eacv  There is a Uworld qx that explain this in detail> ID: 863 +