After several hours of blood draws, a giant needle poke or two, some tears, screaming, and in-depth analysis of the blood levels, we got to enjoy the status quo…for a mere six weeks. But starting Monday night (after our long weekend jaunt to Seattle), Addison’s dose of Tacrolimus will be going up from 3mg twice a day to 3.5mg. I suppose it’s better than the 4mg twice a day – equalling a 50% increase in her dose once again – our transplant team had been pushing on us before the pharmacokinetic (PK) testing.
The PK results showed Addison is metabolizing her main immune suppression drug ‘normally’. And on the day of her test, her trough level was 4.9. Right where her cardiologist wants to see it, somewhere between 4 to 6. That’s the one and only time it’s been in the target zone. Compare this to her pre-PK test levels at 2.1, 3.9, and 2.6. But Addison’s blood tests from this week put her back out of range at 3.9. Hence the request by our team to bump up the Tac dose. Sigh.
At least now that we know her body doesn’t do anything weird with the Tac, such as spike abnormally high levels, we feel a bit more comfortable increasing her dose. It’s such a fine line, and pediatric patients are anything but predictable.
The PK testing is a great tool, but even our transplant pharmacist if the first to acknowledge this an inexact science, “All of this has to be taken with the knowledge that this is a mathematical projection based on our best knowledge. It is a time capture for that day.” I even asked if it would be worth it to get Addison’s labs done more frequently. But she said it wouldn’t be helpful because you could take blood every day for a week and get different numbers each day. Knowing that, you can see why I feel like we are constantly chasing our tails.
I also find it frustrating to see how long it takes innovation to get to the clinic. I have been learning so much about pharmacogenomics, which is the study of how genes affect a person’s response to drugs. Personalized medicine is exactly what pharmacogenomics is all about. Current tests will look at your specific genetic response to hundreds of drugs. Tacrolimus is one of them. There are many companies offering these tests at a fairly reasonable cost of a few hundred dollars. So you might think it would make sense to test all transplant patients to get a better sense of how each person is responding to the drugs, but when we asked about it, we were told that even if the results were ‘interesting’, it currently has no clinical implications. “We wouldn’t know what to do with it.” THIS IS WHY WE NEED RESEARCH!!!
To focus on the good news, her other immune suppression drug Mycophenolate Mofetil, or MMF, is exactly where it should be. All her other numbers look great. She’s doing well. So we keep on living transplant life, and starting Monday, with just a little extra boost of Tacrolimus.
Elaine, Aaron, Addison and Charlie