HIV meds causing false negative methadone tests

[adnrnstudent, ASN, RN]

This phenomenon may be we'll documented in the literature, or well known among you pros, but I'm just running into this.

I've been told that patients taking HIV meds and are also on a methadone program may get a false negative on the methadone when we test them.

I work on a Behavioral Health unit and had patient insist was on methadone but didn't test pos for it. The clinic confirmed patient does indeed take methadone and we found out patients can get false negatives that are on HIV drugs.

I don't know if it's all HIV drugs or just certain ones. I know Atripla for sure involved.

Any comments?

[Meriwhen, ASN, BSN, MSN, RN]

Reasons that the methadone test may be negative:

It's possible that the patient's body naturally metabolizes methadone very fast.

It's possible that another drug is speeding the metabolism and/or excretion of the methadone.

It could be that the patient isn't taking a high enough dose of methadone.

It could be that the patient isn't taking methadone frequently enough to maintain a detectable level of the drug.

It could be that the last done of methadone was a long time prior to the drug test and so has already cleared the system.

It could be that the patient missed a dose of methadone before testing.

It could be that the patient isn't taking the methadone at all. Unless someone is checking every administered dose to prevent cheeking, it's possible that the methadone isn't making it from the mouth down to the stomach. Though usually in addictions, patients more often ARE taking something than they aren't so it's probably not this. But there is quite the market for methadone on the street...

Anyhow...

I've never heard of HIV meds (Atripla, et al.) causing false negatives for drug tests. That being said, it could be possible that they are altering the metabolism and excretion of methadone in some way. What you could do is contact the manufacturers of the medications and ask them if there is a known interaction between the medication and methadone. See what they say...and share it here. I'd be interested in hearing what they tell you.

[latebirdie]

I remember reading that those on methadone who were taking HIV meds had to be in like 3 or 4 times the amount of methadone as a side effect of certain HIV meds. Can't remember which ones though, been too long :-)