If you take Sudafed before diving you should read this article.
This article was sent in by Tim Peever.

I experienced some of these symptoms while diving in Cozumel last year. My philosophy regarding over the counter medicine is " The more you take the faster it will work! ...Wrong, with the overdose I normally take, I experienced anxiety, tenseness, and had respiratory difficulty. I actually aborted one dive. In reality, I should of aborted all dives that week.
Bob

Article by Tom Mount:- Many of us over the years have evolved to diving drug junkies. We begin our dive day with a mixture of coffee, aspirin and Sudafed. In recent months several accidents and near misses have produced concern as to the effects of Sudafed and other decongestants on divers, especially while deep diving and/or gas diving. However the same concerns have also been observed on more shallow air dives.
The opening point of concern occurred early this summer. An EANx cave diver died on a dive well within P02 limits. This was within commonly exceeded air P02 dives. It was noted that the divers blood gases contained a high level of pseudoephedrine, a major ingredient in Sudafed and associated generics. We vaguely questioned if this may have contributed to, or even caused the accident.
A diver using air died while cave diving in Missouri recently. Per his companions he called the dive, then bolted! He had taken Sudafed prior to the dive. On one other occasion he had exhibited the same behavior and survived. Before that particular dive he had once again used Sudafed.
Early this summer a diver accustomed to diving to 160 feet (48 meters) went almost comatose on a dive. His two companions had to maintain his regulator and assist him to shallower water. The only thing he had done different than normal was to take Sudafed prior to the dive.
A Trimix diver on a dive with a reasonable END felt he was losing it. The diver called the dive and made a controlled ascent. Again the only thing different than "normal" was the use of Sudafed preceding the dive.
A few years ago Patti Mount took a 12-hour Sudafed prior to diving and felt really "out of it" once at depth. This included feelings of apprehension and fighting to maintain consciousness. That was her last 12 hour Sudafed taken prior to diving. Patti had similar sensations on a dive, which she made after taking a Benadryl antihistamine tablet for a reaction to a jellyfish sting.
In the seventies while on a saturation dive on Hydrolab, one of my dive partners developed a cold. The dive medic gave the diver Actifed and he went into a coma for two days finally coming out of it once we were well into decompression.
Early this year after taking a Sudafed prior to a deep dive I experienced what I attributed at the time to narcosis, however it was the most severe narcosis I have ever had at a much shallower dive than I routinely make. Since I was on a light Trimix mixture and not air l can only attribute this to the Sudafed.
From Australia, Rob Cason reports Oceaneering International commercial dive company banned Sudafed over ten years ago due to its adverse effects on their divers.
Recent recreational occurrences in Australia as reported by Rob Cason IANTD Australasia, parallel those referenced above. In fact Sudafed warnings have likewise been issued there.
The above incidences are not conclusive as to the adverse effects of Sudafed and/or other decongestants while diving. They do represent grounds for concern and further investigation.

Gary Taylor, IANTD EANx IT#13 sent me a copy of the 1991 PDR description of pseudoephedrine hydrochloride, Sudafed's active ingredient. It states:

ADVERSE REACTIONS include nausea, cardiac palpitations, irritability, excitement, headache, dizziness, tachycardia, diarrhea, drowsiness, stomach pain, SEIZURES, slowed heart rate, shortness of breath, and/or troubled breathing; with an overdose add anxiety, tenseness, and respiratory difficulty.

TREATMENT: Includes the statement, "If convulsions or marked CNS excitement occurs Diazepam may be used."

Certainly this is food for thought. Personally I just gave up a ten-year habit of Sudafed diving. If you or anyone you know has had adverse reactions following a Sudafed or other "decongestant used" dive please forward this information to us. We will pass it on to responsible research / physiologist / physician personnel who are investigating this. If there seems to be a trend we will inform you of such in this journal. Thank you.

IANTD WISHES TO THANK BOTH INSTRUCTOR TRAINERS MARK LEONARD AND GARY TAYLOR FOR CARING ENOUGH TO TAKE THE TIME TO SHARE THE INFORMATION, WHICH LED TO THE RESEARCH OF THIS ARTICLE. WE ALL WANT TO MAKE DIVING SAFER. TOM

The National Sea Grant Library has a "Diving Safely Digital Library". Very informative articles on diving safety.

12 Tips for a Safe and Fun Dive
• Take lessons and get qualified by a certification agency before participating in SCUBA diving.
• Get a form from your doctor and take a swim test before learning SCUBA diving.
• Once certified, do not dive in dangerous waters or in an environment for which you are not qualified/certified, such as: ice, cave, and shipwreck diving. They all require special training.
• Never dive by yourself. Find a buddy.
• Listen to and follow the rules set forth by the person in charge of the dive.
• Check your equipment carefully and check how the equipment functions, especially if you are renting the equipment. Make sure it works properly.
• Know local weather conditions before you go on a dive. Make sure the water and weather conditions are safe.
• Protect your skin by wearing a waterproof sunscreen.
• Drink plenty of water regularly and often even if you do not feel thirsty. Your body needs water when diving.
• Know the signs and symptoms of heat stress and emergency treatment if you are diving in hot weather.
• Know the signs and symptoms of hypothermia and emergency treatment if you are diving in cold weather.
• Wear sunglasses to protect your eyes against the suns damaging rays. Choose sunglasses that absorb at least 90 percent of UV sunlight