Pharmacokinetics

[Firaskais]

Hello.

How imporant is the pharmacokinetics to clinical pharmacists?

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[Firaskais]

What's kinetics???

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huh?

 

[Rouelle]

huh?

I think @msweph is saying that they don’t calculate (ln 2)/k very often.

 

[owlegrad]

Personally I find it so critical that I let a free website do all of it for me.

 

[Firaskais]

Thank you all for your reply

 

[lord999]

Unless you go out of your way to make it your practice (so Maricopa County's Burn unit in Phoenix more or less exclusively treats hard kinetic patients), the average pharmacist either looks at an autocalculated dose by the EMR, looks at a simple protocol, or (in very unusual cases) uses a calculator for it. This is hardly 5% of the majority of hospital pharmacists time unless they decide to make a ritual out of it. And even in scenarios like geriatric (renal/hepatic insufficiency being assumed), the protocols are fairly straightforward.

Pediatrics, burn patients, initial neurological diagnoses (the antiepileptics do require some level of judgment), and amputees are the ones that you *may* consider doing something special for, but even then, this becomes a fair routine after the first year such that even the custom stuff becomes practice habit. If you are going to do kinetics as a significant portion of your time, you have to volunteer for a practice area that has that feature as a job matter.

As for learning it in school, it's more important that you know a couple of things:
1. How the orders work between zeroth (doesn't matter how much a patient weighs or has function, it's a constant) and higher orders (differing things matter)
2. What goes renal versus hepatic and what happens in insufficiency (some drugs becomes suprapotent from concentration, some drugs become worthless as conversion from their prodrug form is now impossible)
3. The idea of the CYP450 system even if you don't memorize the interacting drugs (although that really helps).
4. You should memorize the list of drugs that could have manual kinetics calculations (phenytoin, carbemazepine, aminoglycosides, etc.) simply to remember that if you see an order, there may be more to it than just pressing the button.

 

[El Trombopag]

Kinetics for me is 90+% of the time protocol-driven, the remaining 10% is a combination of global rph, an online half-life calculator, and/or common sense. There is basic stuff that just comes with experience— obese elderly, e.g.

 

[Firaskais]

Unless you go out of your way to make it your practice (so Maricopa County's Burn unit in Phoenix more or less exclusively treats hard kinetic patients), the average pharmacist either looks at an autocalculated dose by the EMR, looks at a simple protocol, or (in very unusual cases) uses a calculator for it. This is hardly 5% of the majority of hospital pharmacists time unless they decide to make a ritual out of it. And even in scenarios like geriatric (renal/hepatic insufficiency being assumed), the protocols are fairly straightforward.

Pediatrics, burn patients, initial neurological diagnoses (the antiepileptics do require some level of judgment), and amputees are the ones that you *may* consider doing something special for, but even then, this becomes a fair routine after the first year such that even the custom stuff becomes practice habit. If you are going to do kinetics as a significant portion of your time, you have to volunteer for a practice area that has that feature as a job matter.

As for learning it in school, it's more important that you know a couple of things:
1. How the orders work between zeroth (doesn't matter how much a patient weighs or has function, it's a constant) and higher orders (differing things matter)
2. What goes renal versus hepatic and what happens in insufficiency (some drugs becomes suprapotent from concentration, some drugs become worthless as conversion from their prodrug form is now impossible)
3. The idea of the CYP450 system even if you don't memorize the interacting drugs (although that really helps).
4. You should memorize the list of drugs that could have manual kinetics calculations (phenytoin, carbemazepine, aminoglycosides, etc.) simply to remember that if you see an order, there may be more to it than just pressing the button.

Thank you so much for your clarification. I'm a actually a pharmacy student and I will be taking pharmacokinetics after a few weeks so I was just wondering if it's really important to clinical pharmacists.. anyway thanks again!

 

[flip33]

The concept of pharmacokinetics is important, but it's like engineering where very few engineers use calculus after they graduate.

 

[CetiAlphaFive]

Unless you go out of your way to make it your practice (so Maricopa County's Burn unit in Phoenix more or less exclusively treats hard kinetic patients), the average pharmacist either looks at an autocalculated dose by the EMR, looks at a simple protocol, or (in very unusual cases) uses a calculator for it. This is hardly 5% of the majority of hospital pharmacists time unless they decide to make a ritual out of it. And even in scenarios like geriatric (renal/hepatic insufficiency being assumed), the protocols are fairly straightforward.

Pediatrics, burn patients, initial neurological diagnoses (the antiepileptics do require some level of judgment), and amputees are the ones that you *may* consider doing something special for, but even then, this becomes a fair routine after the first year such that even the custom stuff becomes practice habit. If you are going to do kinetics as a significant portion of your time, you have to volunteer for a practice area that has that feature as a job matter.

As for learning it in school, it's more important that you know a couple of things:
1. How the orders work between zeroth (doesn't matter how much a patient weighs or has function, it's a constant) and higher orders (differing things matter)
2. What goes renal versus hepatic and what happens in insufficiency (some drugs becomes suprapotent from concentration, some drugs become worthless as conversion from their prodrug form is now impossible)
3. The idea of the CYP450 system even if you don't memorize the interacting drugs (although that really helps).
4. You should memorize the list of drugs that could have manual kinetics calculations (phenytoin, carbemazepine, aminoglycosides, etc.) simply to remember that if you see an order, there may be more to it than just pressing the button.

There was a pharmacist that I met who served as my sub-preceptor when mine wasn't available.

She'd do it all via TI-89, put in some Q18 hour order, then it'd be promptly changed by the ID MD, and she'd get chewed out at rounds.

 

[Rubisco]

The majority of us use calculators and protocols. Those long winded calculations/formulas you do in school isn't done on a day to day basis (in my opinion if you did everything but hand that just introduces more room for a calculation error). I think school just tries to illustrate the idea behind the concepts.

It's like writing out pages of proof of why E= mc^2; we just plug it in and use clinical judgement (on special considerations) for work

 

[confettiflyer]

Important, but we use calculators and tools to cut out unnecessary calculation time.

BUT in order to apply clinical judgment, you need to have a deep understanding of how those tools work and what the variables represent.

Don’t be the dummy who’s chasing tobra levels on a hemodialysis patient because you don’t understand the underlying concept of what hemodialysis does to someone’s volume of distribution.

EDIT:
Okay dialysis is a bad example for kinetics, but just sayin’....know your tools before you use them.


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[Firaskais]

Important, but we use calculators and tools to cut out unnecessary calculation time.

BUT in order to apply clinical judgment, you need to have a deep understanding of how those tools work and what the variables represent.

Don’t be the dummy who’s chasing tobra levels on a hemodialysis patient because you don’t understand the underlying concept of what hemodialysis does to someone’s volume of distribution.

EDIT:
Okay dialysis is a bad example for kinetics, but just sayin’....know your tools before you use them.

Thank you.

 

[nampa]

Kinetics for me is 90+% of the time protocol-driven, the remaining 10% is a combination of global rph, an online half-life calculator, and/or common sense. There is basic stuff that just comes with experience— obese elderly, e.g.

I use global and clin calc for vanc. Nomogram for amino I adjust vd for weight bmi and lower for renal, but it doesn’t reach Target trough enough.
Additionally how do you guys deal with creatinine below 30 with non traditional dosing and lack of in house blood values for aminos

 

[confettiflyer]

I use global and clin calc for vanc. Nomogram for amino I adjust vd for weight bmi and lower for renal, but it doesn’t reach Target trough enough.
Additionally how do you guys deal with creatinine below 30 with non traditional dosing and lack of in house blood values for aminos

No amg levels??

“Patient?! CAN TOU HEAR ME??”
“Patient...are you peeing?”

That’s about it.


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[nampa]

No amg levels??

“Patient?! CAN TOU HEAR ME??”
“Patient...are you peeing?”

I’ve seen barnes jewish nomogram used. Didn’t know if other hospitals used traditional dosing instead

 

[confettiflyer]

I mean you can reasonably estimate peak so at least you know you’re being efficacious, but using an amg in a renally impaired patient with no levels available sounds like a really bad idea.


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[nampa]

I mean you can reasonably estimate peak so at least you know you’re being efficacious, but using an amg in a renally impaired patient with no levels available sounds like a really bad idea.

I meant I have seen barnes jewish nomogram used with these patients. Is this common

 

[PolarPop]

I meant I have seen barnes jewish nomogram used with these patients. Is this common

Most hospitals use nomograms but even then you still need to get a level to use them. You are asking for a lawsuit if you are giving more than one dose of these drugs without levels in a country like the US.

 

[nampa]

Most hospitals use nomograms but even then you still need to get a level to use them. You are asking for a lawsuit if you are giving more than one dose of these drugs without levels in a country like the US.[
We get a level but it takes a couple days. In the meantime we use barnes jewish nomogram as opposed to the hartford because the former can dose crcl under 30

 

[lane one]

I think PK is actually pretty important. Not the math stuff, but the conceptual stuff. Vd and t1/2 are probably the most important. Sure there are nomograms for AG and Vanc but there are plenty of other applications. Anticoag transitions, dose timing for desired effect of certain meds, antipsychotics, benzos, when to use reversal agents and when not to....the list is endless.