DAN recently reported this:
SPAM -- ignore™/SPAM -- ignore™ and the Risk of Oxygen Toxicity - "Reports to DAN suggested that oxygen toxicity risk might be increased by these drugs. This was found to be true in a rat model."
Do you have any information regarding this? Should men not take SPAM -- ignore before diving NITROX? If so, how long do they have to wait to dive after taking SPAM -- ignore? I believe the article in Alert Diver (page 87. Winter 2013) suggested that men on SPAM -- ignore change their partial pressure setting (or avoid high partial pressure). What should a man with SPAM -- ignore in his system consider his upper limit on partial pressure? Duke University was doing the research, as I recall. Any input would be appreciated. AxxxR.”
The material to which you are referring is mentioned within the text of a paragraph entitled "Oxygen Toxicity and Erectile Dysfunction Drugs" by Dr. Petar Denoble (Senior Director of DAN Research). It appears on page 87 of the Winter 2013 issue of Alert Diver. The conclusions are at least in part based on work done by Dr. Ivan Demchenko and colleagues at the Center for Hyperbaric Medicine and Environmental Physiology, Duke University Medical Center. Findings of note to your inquiry include a reduction in seizure threshold in rats given PDE-5 inhibitors (such as SPAM -- ignore (sildenafil) & SPAM -- ignore (tadalafil)) under conditions of hyperbaric 02. You may read the abstract of the study here -->
Demchenko, IT; Ruehle, A; Allen, BW; Vann, RD; Piantadosi, CA. EFFECTS OF PHOSPHODIESTERASE-5 INHIBITORS ON CEREBRAL BLOOD FLOW AND SEIZURES IN RATS EXPOSED TO HBO2. (Abstract) Undersea Hyperb Med. 2008 July-Aug;35(4) RRR ID: 7893 ([abstract] EFFECTS OF PHOSPHODIESTERASE-5 INHIBITORS ON CEREBRAL BLOOD FLOW AND SEIZURES IN RATS EXPOSED TO HBO2.)
Another related & informative work can be found at --> Demchenko, IT; Piantadosi, CA. Nitric oxide amplifies the excitatory to inhibitory neurotransmitter imbalance accelerating oxygen seizures. Undersea Hyperb Med. 2006 May-Jun;33(3):169-74. RRR ID: 5056 (http://archive.rubicon-foundation.or
I'll only mention in passing that there can be multiple issues in generalizing findings from studies done on rodents to humans. You'll also want to note that the rats in the experiment were compressed to 6 ATA 02.
As mentioned in the Alert Diver paragraph, of importance is the effective duration of the chosen medication. In this regard, studies show a plasma elimination half-life for SPAM -- ignore (sildenafil) of about 3–4 hours. As might reasonably be inferred from the ads for SPAM -- ignore (tadalafil), it's half-life is very much longer, on the order of 15-18 hours. Of course for those on once-daily chronic administration, plasma levels don't decrease for the duration of the regimen. Clearly these facts can have implications for the diver and should be discussed with an appropriately knowledgeable physician.
There simply isn't enough known about this topic to allow for accurate & detailed answers to questions such as, "What should a man with SPAM -- ignore in his system consider his upper limit on partial pressure?" What can comfortably be said is that based on theory and very limited research in rats, a diver taking erectile dysfunction medication of the PDE-5 inhibitor class might be prudent to control plasma levels during dives and to dive profiles designed to minimize pp02 such as diving air rather than EAN and keeping depths relatively shallow.
This is educational only and does not constitute or imply a doctor-patient relationship. It is not medical advice to you or any other individual and should not be construed as such.”