| Transcript |
"So today I'm going to be talking about hydroxychloroquine, also known as Plaquenil. You need to know about this, and you can watch the hydroxychloroquine video about what the current American Academy of Ophthalmology guidelines are for this, but in Neuro-Ophthalmology the thing that we face is when patients have both idiopathic intracranial hypertension (IIH) and hydroxychloroquine on board then it changes a little bit what we do and makes it a lot more difficult to follow these patients. Hydroxychloroquine as you know is Plaquenil, it's used for a wide variety of conditions, but the most common indications that we see are rheumatoid arthritis and lupus. You need to know the dose, and the toxicity occurs at doses as low as five milligrams per kilogram, so you need to know the patient's weight. And so that's already one of the problems when you have IIH, which is typically in an obese female, that is a risk factor for both the hydroxychloroquine toxicity and the pseudotumor cerebri. So, you need to calculate their dose. You really should be starting to think about high risk as soon as you get to 6.5 milligrams per kilogram dosing. Most patients are on 200 milligrams twice a day, which is 400 milligrams; and at that level of dosing the risk is moderately low. So, then the second thing you need to know is the duration: how long have you been on the drug; and the cumulative dose threshold that we are worried about is one kilogram. That normally doesn't occur until you're five years into therapy and so normally we don't really even have to worry about screening these patients until year five. However, the current recommendations are to follow the patient yearly, just like regular people over age 35, which is the current academy recommendation for regular people. The dose and the duration are important but there are other things that are important as well, which include patient-related factors. The patient-related factors are whether they have liver or kidney disease; and in patients who have lupus as their indication for Plaquenil, we have to worry about glomerulonephritis and secondary renal dysfunction. The dose has to be modulated if you have renal failure and the risk goes up, a lot, if you have renal failure and you're on hydroxychloroquine. So you got really got to be thinking about the lupus nephritis patients, in this setting. In addition, you know about the weight and then the age. The age isn't as important but the older patient, over age 60, is moving into a higher risk, as well as previous macular disease. So if you have a previous age-related macular degeneration or you have a, some other comorbidity like IIH, it's going to be a lot harder to follow these people. Now, the screening recommendations for the hydroxychloroquine are slightly different than what you would do on an IIH patient so normally in IIH, we're doing a 24 or a 30-2 Humphrey, but in hydroxychloroquine toxicity, because we're looking at the central macula for the bullseye maculopathy that is a 10-2 field. You should also know that in Asian people they're more likely to have the peripheral version and so Asians need both the 24-2 and the 10-2. As opposed to IIH where we're only doing the 24-2. The second thing is, OCT (Optical coherence tomography) and we're going to do macular OCT for hydroxychloroquine, versus the optic nerve OCT that we're doing in IIH; and we need to make sure that we're doing the spectral domain OCT of the macula because it's higher resolution. You should not be using the time-domain OCT. The last thing is we have to have some sort of structural imaging and that's either OCT or fundus autofluorescence, but not fluorescein angiogram. We could also do an electrical test and that's MERG (multifocal electroretinogram) but that's not universally available but not the ERG (electroretinogram), the full-field ERG is no go, we don't want to be doing that. We're going to be taking a fundus photograph at baseline especially if they have pre-existing macular disease so that you know what that fundus looked like in advance. So we need a Humphrey, not the 24-2, unless you're Asian, a 10-2, we need one of the following: either OCT fundus autofluorescence or multi-focal ERG. Because multi-focal ERG is not normally available, you're really down to spectral-domain OCT and fundus autofluorescence; and then an IIH patient that means we have to do the OCT of the macula and the optic nerve; and that's a problem because normally the insurance company is not going to pay for both, so you're going to have to take a hit here. You're also going to have to take a hit here because we can only do one field. They're only going to pay for one of those. So, in order to do the right thing in a hydroxychloroquine plus pseudotumor patient, you as the doctor have to take a little bit of a hit; and that means we have to take the loss on doing the right test, which is OCT of the macula and optic nerve, two visual fields. So, this is also a problem, and having to take a fundus photograph of the disc and the macula. So, it's a big problem when we have hydroxychloroquine and IIH, and so normally I'm going to write to the prescribing doctor of this one and say, "hey do we really need this medicine because you're making it really hard on me, and also it's really hard to get paid for all the tests that are going to be necessary to do the standard of care for both of these conditions. So, it'd be a lot easier on me, if you just chose something else here. However, if that's the best medicine we still got to do what's best for the patient." So, in summary, you need to know a little bit about hydroxychloroquine, the risk factors on the patient side, the risk factors on dose duration, and cumulative dose. That the workup is totally different: 24 versus 10, except in Asians. Spectral-domain and not time-domain OCT of the macula, and multifocal ERG but not full-field ERG. Take a photo, document everything, explain it to the patient and it'd be better if you didn't have to do both." |
