Drug interactions with Zofran for nausea

[Tsadeeq]

I have been taking Zofran (ondanstron) for nausea for a couple of months now and was wondering whether there is anything known about drug interactions between this drug and HIV (and other) meds.  Since Zofran is usually only used for short periods during cancer chemotherapy and is almost never used for sustained periods, I thought this might explain the lack of data in regular databases (including the AIDSMEDS database).  I therefore thought that somebody here might have experience with taking Zofran continually or might be able (and/or willing) to track down studies from other sources, such as the manufacturer, GlaxoSmithKline.
Incidentally, in addition to completely clearing the nausea, it has been of enormous help with my peripheral neuropathy.  After 15 years of only moderate control with opiates, I am almost opiate-free for the first time.  That has been an amazing positive side-effect!
Thanks!
- David

[allopathicholistic]

that's good to hear about it helping your nausea and PN  ... of course you totally need to ask your doctor about the interactions ... . what do you plan on doing if the doctor says not to overuse it? you did say it is almost never used for sustained periods

[newt]

There are no known interactions with ARVs.  Based on what is known about the chemsitry of this drug, in therory there may be a (probably not serious) intereaction with tipranavir (Aptivus).

University of Liverpool HIV Drug Interactions website

[Tsadeeq]

Thanks Newt:
I figured I might get a helpful answer from you and I was right.  I would be most interested in setting up a dialogue with you.  I believe my email address is available on the site but, if not, I can send it through this thread.  Incidentally, I am a retired professor of Pharmacology, which is why I asked the very specific question that I did!
- David

[gerry]

David,

I didn't find any studies specific to your inquiry.  I guess that's partly because it's not used that commonly in this setting.  The drug itself does not induce or inhibit P450 so theoretically, it should not affect the metabolism of ARVs.  It's metabolized extensively in the liver and can be affected by P450 inducers, but there are no dose adjustment recommendations, even with anticonvulsants.

I'm very intrigued by your experience regarding improvement of PN symptoms when you started Zofran, especially since you were requiring opiates to control it prior.  Did you notice it immediately or did it happen gradually?  You might be on to something here.

Gerry

[Tsadeeq]

The effect on the PN pain was immediate and is still apparent.  I am taking far fewer opiates for my pain control than before.  I have done a little search of the literature and it is known that 5-HT3 receptors (at which ondansetron is an antagonist) are known to be involved in spinal nociceptive (pain retransmission) mechanisms.  One paper of particular interest can be found at the following website and I suggest that you read the abstract at least: http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=14570668&dopt=Abstract.  There are a number of other references on the subject and another interesting one can be viewed at: https://www.haworthpress.com/store/ArticleAbstract.asp?sid=X9J3RKU7E9VA9G4PTVL0VCU0V5DAE187&ID=51229.

Thanks for your interest!

Incidentally, I have myself published several papers on ondansetron and other 5-HT3 drugs and had hoped that the drug company might feel inclined to provide me with the stuff for free.  The cost through my insurance is $3,000 per month, but some Canadian pharmacies are a whole lot more dollar-friendly if anyone needs to know.