Sudafed and Oxygen Toxicity

[Wordmonger]

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.

 

[The Iceni]

Wordmonger once bubbled...
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?

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.

 

[Dr Deco]

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.

Money:$:

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.”

Surveys

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:

 

[The Iceni]

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,