Sudafed and Oxygen Toxicity

Discussion in 'Diving Medicine' started by rebharrop, Jul 26, 2002.

  1. rebharrop

    rebharrop Angel Fish

    Heh there medical peeps,


    Wonder if I can ask for a few opinions.

    I have always found that if I take a Sudafed the night before a dive (or even some days before) it makes ear equalisation sooooo much easier for me - both during and after diving.

    Now, I am just about to do my nitrox course and I have read that Psuedoehredrine (in Sudafed) is known to be a CNS exciter and so I am worried that taking Sudafed (even >24 hours before diving) may predispose me to oxygen toxicity.

    My LDS dive instructor effectively said not to worry too much about oxygen toxicity, and if something I am doing is making it considerably easier to dive then keep doing it.

    I would be interested in a second opinion (just to put my mind at ease) and/or any recommendations for alternatives.

    I know of the concerns about diving under the influence of decongestants of them 'wearing' off during the dive and you ending up with a reverse block. However, I suspect in my case that because I am taking it days before, the Sudafed is loosening the fluids in my ears and nose and throat subsequent to the dives and I am not 'under the (direct) influence' of the drug during the dive.

    What do we think?

    Kind regards
  2. iainwilliams

    iainwilliams Nassau Grouper

    # of Dives:
    Location: Hobart, Tasmania, Australia
    Hi - First of all taking any type of decongestent is not really a "good idea" before diving for the reasons you already have stated.

    Individual sucepability to CNS oxygen toxicity is not very well understood. Some divers "appear" to be not affected by high PO2 pressures, whilst others are effected above the currently established PO2 limits. Symptoms vary as does whether an affected diver suffers a convulsion (grand mall) or not.

    Sudafed which contains pseudoephedrine is a decongestant. pseudoephedrine as per the MIMS can cause hallucinations, palpatations, sweating, urinary retention and CNS disturbances. A diver's predisposition to CNS toxicity can be increased by all of the above to varying degrees. CO2 can also be a contender to increases risk of CNS disturbance.

    I am not sure what degree you may be affected (if at all). If I was takling this medication I would not dive to the maximum PO2 for the EAN mix I was using, but rather dive more conservatively.

    Dive safe Iain
  3. Wendy

    Wendy Divemaster

  4. NetDoc

    NetDoc Chairman of the Board

    as usual. Those are GREAT links.

    I went to a steroidal nasal spray (prescribed) precisely because of my chronic congestion. Now that the "cycle" has been stopped, I don't seem to get as congested anymore anyway... go figure. There are -no- undeserved hits, of Oxtox, CNS, or even DCS... just episodes that we don't understand. Stay safe... avoid Sudafed while diving NitrOx. Share this with your instructor too... it is his duty to keep you as safe as possible, and not his right to diminish what the medical community reccomends. Everyone likes to see themselves as the exception and not as part of the bell curve.
  5. rebharrop

    rebharrop Angel Fish

    Nice links - Dear God! So it seems that these statements in our Padi scuba manuals are based on no solid scientific experimentation and/or case study analysis! No association or cause and effect relationship between pseudoephedrine and CNS oxygen has never even been established and the 'workshop' cited in the Padi nitrox textbook has no formal write up!

    There's just a few individual cases of people using sudafed (and sometimes other confounding drugs) and then diving (sometimes beyond recreational limits) and it may or may not have been related!

    My apologies, as someone who gained a science degree, I just assumed that there was FACTUAL or experimental evidence to support the safety concerns raised. Silly me :stupid: (not).

    The other article which talks about the Naval studies at least indicates that there was some formal experimentation used to set the O p.p. limits, but most of the studies use extreme exposures and the unfortunately casualties were divers doing strenous exercise normally at over 1.6 ata. (Since, I just wanna float around looking at fish, well within recreational limits - I'm less worried now).

    Thank you Wendy for the links. You were right they really did help.

    Especially this:
    What's the bottom line? In normal, healthy divers breathing air, occasional use of pseudoephedrine at the recommended dose is probably safe. This presumes that the drug has been taken during periods when no diving has occurred and that no undesirable reactions have occurred. However, one should avoid chronic (daily) use when diving, and it seems reasonable to avoid the drug entirely if diving while using oxygen-nitrogen mixes where the PO2 during a dive might exceed 1.4 ata, the current recommended "safe" open-circuit scuba limit.

    Fine. As a healthy, young sensible recreational diver who doesn't take any form of regular medication. I think I can probably continue to take the odd sudafed days before a dive if it makes the fluid in my ears decongest so they won't give me pain during a dive days later. I have no intention of going over 1.4 ata on Nitrox (or deeper than recreational limits on air for that matter).

    More to the point though. WHY are there no formal scientific studies? Here's another article: ( that answers some of the issues but raises more. Why are they not asking these questions when incidents come into hyperbaric chambers or hospital?
    Or even forget that - there are enough recreational divers out there that can be reached through websites like this one. Even if you don't test emperically you could have an online questionnaire to find out how many divers have used various medications etc. and, if any, to what bad effects.


  6. The Iceni

    The Iceni Medical Moderator

    Hi Becky,

    Acute CNS oxygen toxicity is something I am very interested in and there is good biochemical theory to suggest all systemic stimulants predispose to an oxtox hit and should be avoided in Nitrox divers. Could I suggest you take a close look at the neighbouring thread?

    On the Ask Dr Deco part of this forum there have been a number of threads on CNS oxtox, which is quite unpredictable as we do not yet know the biochemical mechanisms involved at the cellular level. While I do have my ideas they are unlikely to be tested on human volunteers. In general you are safe with a pp O2 of less than 1.4 bar.

    If you want to be blinded by science see also the posts at;
  7. Dea

    Dea Nassau Grouper

    I had a very bad experience diving on Nitrox with Sudafed. Though it was not due to oxtox.

    I had a slight congestion that day so I took one Extra Strength Sudafed about an hour before my first dive (on Nitrox) I was able to equalize and the first dive went fine.
    Before the second dive, fearing the reverse block if the med should wear out underwater I took a second one. Just to be safe.
    That was a big mistake.

    Just when I was descending, I felt severe itching in my eyes and they started running like crazy. Than the nose of course joined. The tears kept coming and coming. I had to clear my mask every few minutes. Vision was blurry, eyes were itching and stinging. I flooded my mask with cold water completely, hoping to get some relive, but that did not help. Due to some circumstances I could not call it a dive, and so just concentrated on getting through it. I was very stressed and ate all the air in my tank in 40 min.
    Than came up completely exhausted, and my eyes continued to run for about an hour after that.

    I know I should not have taken the second one... And I'm not sure if Nitrox played any part in my experience being so severe.
    But since both Sudafed and Nitrox were present, I decided to post it.

    P.S. I am never doing that again!
  8. John Reinertson

    John Reinertson Barracuda

    There are theoretical concerns regarding stimulants and oxygen toxicity, as mentioned above.

    There are no clear studies regarding Sudafed and its potential effect on divers at ppO2 of 1.4 or so.

    I wish there were studies. Stop to realize, though, that if seizures occurred at 1 per 10,000 dives at a Partial pressure of 1.4ATA, (A figure which is almost certainly on the high side)
    and if Sudafed raised the risk of convulsions by 50 % ( which is probably also high) and it would take about fifteen convulsions to determine the risk with any degree of statistical reliability, it would take 6,600 times 15 dives to determine this relationship.

    In other words, you'd have to do a total of 99,000 nitrox dives with Sudafed to make a reliable study.

    If you're looking for paid volunteers, make me an offer.

    The US Navy doesn't prohibit Sudafed in diving. (or at least they didn't at the last course I attended.)

    That's not the same as saying it's risk free, but there are a lot bigger risk factors out there.

    Continue to dive safe.. keep the bubbles in the water and not your bloodstream..

  9. Rickg

    Rickg Manta Ray

    # of Dives: 500 - 999
    Location: San Diego, CA
    Please excuse my last post. I was going to quote part of John's post but hit the wrong button.

    John is correct in that the USN didn't restrict the use of Sudafed for divers (at least as recently as '96 when I retired). I am not a Navy diver but frequently dove with them while on Guam and Midway Islands. At that time there were 2 over-the-counter medications they could take without seeing a diving physian - one of which was Sudafed (the standard 30 mg variety) and the other was aspirin. I don't know what they say about the newer, long lasting versions Sudafed.

    I also knew several diving physians that were on-call for the recompression chamber and they would frequently take 2, 30 mg Sudafed while enroute to the chamber when responding to emergency calls. The actual term they used to describe Sudafed was "diver's candy". FYI, most of the calls they received were in response to sport divers that had gotten bent and not Navy divers. There are many sport divers on Guam that are very thankful the US Navy had a chamber on the Submarine Tender there.

    I can tell you from personal experience that I routinely take Sudafed for the first several days of an extended dive trip even if I don't have any congestion just as a preventative. I usually start it 30 minutes prior to flying and then continue to take it 2-3 times a day for 2-3 days when on an extended dive trip. After several days of using Sudafed it seems that I have a much easier time clearing my ears even after I discontinue taking it. I have never had a problem using Sudafed in this manner nor have I ever experienced a reverse block while doing so.

    That said - this is by no means encouragement for someone else to try this. It is only my own experience with taking Sudafed.

  10. Rickg

    Rickg Manta Ray

    # of Dives: 500 - 999
    Location: San Diego, CA
    Several things I forgot to mention when I sent my earlier post.

    1) All my diving was on "air"
    2) Max depth was 160'
  11. Wordmonger

    Wordmonger Angel Fish

    This argument has never made any sense to me and here is why. When a person takes meds -- any meds, not just sinus meds -- the objective is to "stay on top" of the meds, which means to take a pill every X hours. Now, unless one is on a really long dive -- as in hours, which is pretty unlikely -- how would the med wear off? So, say you take your pill for whatever ails you every 8 hours -- 8 a.m., 4 p.m., midnight -- and you know that you are going diving at 7:45 a.m., 3:45 p.m. and 11:45 p.m. Most folks simply adjust their pill schedule a couple of days before, or take the rather small risk that the meds will probably not wear off by 8:30, 4:30 or 12:30 -- assuming that the pill taker has stayed on top of the meds for a long enough period of time in the first place.

    I am considerably more interested in the 02 toxicity issue. That sounds like a more valid concern.

    And, by the way, I have terrible sinuses and when the world is in bloom, I take meds every single day, whether I'm diving or not. I've never had sinus meds "wear off" during a dive and know a lot of other divers with bad sinuses who take meds regularly -- and not a reverse block in the lot. Not to say there aren't those who haven't had the experience -- there must be, because it's such a common warning -- but it seems like common sense and planning would prevent the "wearing off" problem.
  12. The Iceni

    The Iceni Medical Moderator

    Hi Wendy, Wordmonger et al,

    Can I just add a bit more to this thread?

    The effects of almost all medication "wears off" in time. This is why patients have to keep taking their tablets. The vast majority are excreted by the liver, or by the kidneys in proportion to their concentrations, so they have half times just like dissolved gasses.

    From my perspective there are two main considerations with diving and medication.

    The first is the severity of the condition being treated is far more important that the effects and side effects of the medication taken to treat it. For example the long term damage caused by hypertension includes heart failure and an increased risks of heart attack and stroke so hypertension must be controlled in any diver and it would be a very foolish diver indeed to stop his medication for a dive because of any risks of side effects.

    The second is when treating minor conditions such as nasal congestion with remedies such as sudafed, where you are treating the symptoms and not the cause. Thus if such remedies are used (they are not really treatments) there seems little point in taking them too early as the effects obviously wear off with time. In general, as I understand it, few divers have problems with with "reverse block" on ascent as the higher pressure air in the nasal cavities and the middle ear can (more) easily escape. The majority only have problems on the way down so in the case of sudafed, in my opinion, any wearing off effect is irrelevant.

    On the other hand, for any medication to be effective it must be taken at the right time to acheive therapeutic levels at the target organ. This is when it also produces its more general side effects. (and why I personally prefer locally acting agents such as xylometzolone.)

    So. Sudafed does indeed work and is reasonably safe with respect to CNS excitability but like all drugs should not be abused and only used when needed. Also as Iain said before "If I was taking this medication I would not dive to the maximum PO2 for the EAN mix I was using, but rather dive more conservatively". I doubt we will ever have any scientific studies to cofirm what appears to be simple common sense.

    In fact pseudoephedrine stops working at all after only a few days continuous treatment which is when some patients actually get a rebound effect with a severely running nose, streaming eyes etc.

    Hope this helps.
  13. Dr Deco

    Dr Deco Loggerhead Turtle

    # of Dives: I just don't log dives
    Location: Issaquah [20 miles east of Seattle], Washington.
    Dear Becky and Readers:

    Concerning the issue, “Why do we not have scientific data on this topic?”

    National Interest

    Recreational activities are not high on the list of national health issues. It is probably considered a minor problem even for those involved. It is certainly an elective activity.

    Governments are more interested in problems associated with cancer, stoke, and cardiovascular disease. Sometimes, political action groups will influence priorities beyond their actual general medical importance.


    There is only so much money, and research is not necessarily cheap. Research with graduate students will be less costly (on a per year basis), but can require more years because of inexperience. Additionally, few graduate students are in this field, since there is no future (that is, monetary returns) for someone with an advanced degree in barophysiology.

    Research proposals

    Research is largely funded by competitive proposal submitted by scientists. For better or for worse, “organ systems physiology” has not been an “in” topic for the past several decades. We are in the area of molecular biology. Barophysiology, being more of an “organ” discipline, is not looked upon with much favor by the general scientific establishment. We are sort of dinosaurs in the scientific world.

    Human Subjects Research

    Even if funding was available for studies such as Sudafed and CNS toxicity, such studies are not easily performed under conditions as they currently exist. In this case I am speaking of legal concerns. I have had numerous arguments with individuals at NASA who did not wish to approve a study, but were not concerned that it could occur in space (where an individual could not easily be treated). It is a case of, “On whose watch does it occur.”


    These are not uncommon but are not considered to be of tremendous value. It can give you some idea, but you do not know how representative it is. For example, let us say you wish to determine the experience of divers with Sudafed. You cannot send a letter to all 2 million recreational divers, so you send a survey form to 5,000. Typically you will get back 10% or 20% of these. Why did the other not return the forms? Did nothing happen? Did they not use the drug? Did they have a bad experience and were reluctant to acknowledge their poor judgment (“in denial”)? Did only the very worst cases respond?

    From a survey, you are not sure what you have when you are finished. Naturally, some information is (probably) better than nothing. This is, however, what you have in the PADI book. It is “anecdotal” information, garnered from comments made by scientists and divers around the country. They print it, I guess, because it is better than nothing, but it is not necessarily backed by good data.

    Dr Deco :doctor:
  14. The Iceni

    The Iceni Medical Moderator

    I would love to see much more research into CNS oxygen toxicity itself as this is an area that is very poorly understood.

    As we say in England, "fat chance!"

    Kind regards,

Share This Page