Decongestants and Diving

By Dr. Sawatzky

Decongestants are defined as "agents that reduce congestion or swelling" and are some of the most commonly taken over-the-counter (OTC, prescription not required) medications. In this column, I will look at the various decongestants and explain what divers should be aware of when taking these drugs and diving.

One of the most common problems people suffer is swelling of the mucous membranes that line the nose and sinuses, and excess production of mucous by these membranes. The common cold (a viral infection) and other infections, as well allergic reactions (allergic rhinitis or hay fever) cause the blood vessels to dilate and become engorged. This results in swelling of the mucous membranes, and increased production of mucous.

The significance of this problem is that when the mucous membranes swell and excess mucous is produced, the openings to the eight facial sinuses and/or the openings to the two eustachian tubes connecting the throat to the middle ears can be blocked.

Divers HAVE to be able to equalize these spaces to dive and therefore, many divers will take decongestants before some or most dives. This does not normally cause any problems but in some circumstances, it could result in a dead diver. If the problem is allergies, antihistamines are also commonly taken. Decongestants, antihistamines, and other drugs are often combined in one medication. Antihistamines will be discussed in the next column. Decongestants can be taken by mouth, or in the form of nasal sprays or eye drops.

Most decongestants belong to the class of drugs called 'sympathomimetics'. These drugs stimulate the sympathetic nervous system, or they have effects similar to the sympathetic nervous system. One of their effects is to constrict the blood vessels of the mucous membranes lining the nose and sinuses by stimulating the alpha-receptors on the blood vessels. This causes a reduction in swelling of the mucous membranes, and a reduction in the production of mucous. Unfortunately, all of the sympathomimetics can also interfere with the action of antihypertensive (blood pressure) medications. Some may cause a fall in BP while others may cause a rise in BP. All of them may cause a serious rise in BP if you are also taking, or have taken within the past 14 days, a monoamine oxidase inhibitor (an older class of drugs used to treat depression).

Topical decongestants, sprayed directly onto the mucous membranes, start to work very quickly and have very few adverse effects because the body absorbs only small amounts of the drugs. Decongestants taken by mouth take longer to work than nasal sprays, but may last longer. They also are much more likely to cause adverse effects such as increased heart rate, elevated blood pressure, trembling, and anxiety. This is because any medication taken by mouth is distributed to all tissues of the body, not just the tissues you want to effect. The problem with nasal sprays is that you may not be able to deliver the drug to the swollen mucous membranes you want to effect because of the swelling.

If any decongestant, both topical and systemic, is used excessively or for too long, when the drug is stopped the blood vessels will dilate, the mucous membranes will become engorged and mucous production will be increased. This is called 'rebound congestion'. It can be avoided by using the drugs as directed, and only for a maximum of three days at a time. It is extremely unwise to get into the habit of taking a decongestant before every dive, 'just in case' you have problems clearing.

The most commonly used decongestants are Oxymetazoline, Phenylephrine, Phenylpropanolamine, Pseudoephedrine, and Xylometaxoline. Oxymetazoline, Phenylephrine, and Xylometazoline are available as nasal preparations (sprays) while Phenylephrine, Phenylpropanalomide, and Pseudoephedrine are available for systemic use (pills). The medications listed in the following paragraphs are available in Canada in 2003, as listed in the current Compendium of Pharmaceuticals and Specialities (CPS). This is the most commonly used reference for drugs available in Canada, but it is not completely comprehensive and some available drugs are not listed. Medications available in the USA and other countries often contain the same active ingredients but are frequently marketed under different trade names.

Oxymetazoline is a common, long lasting decongestant (up to 12 hours) found in nasal sprays and eye drops. It is the sole active ingredient in Claritin Allergic Congestion Relief, Claritin Eye Allergy Relief, Dristan Long Lasting Nasal Mist/Spray, and Visine Workplace Eye Drops. Oxymetazoline commonly causes nasal congestion (the symptom it is supposed to cure). Overdose may cause palpitations, headache or sleeplessness.

Phenylephrine is another common decongestant and it is found in nasal sprays, systemic medications and other formulations including a gel for use on hemorrhoids! It is moderately long lasting (4 to 6 hours) and less potent than some of the other drugs in this class. It is the sole active ingredient in Mydfrin, and is found in combination with other drugs in 20 medications listed in the 2003 CPS. It commonly causes blurred vision, headache and rebound nasal stuffiness. Overdose may cause palpitations.

Phenylpropanolamine is not currently in any of the medications listed in the 2003 CPS. It is another sympathomimetic and has been noted to cause significant rises in blood pressure if taken to excess. It has an effect on mood and has been used in weight loss medications.

Pseudoephedrine is the most commonly used decongestant and it is the sole active ingredient in Contact Cold 12 Hour Relief Non Drowsy, Eltor 120, Pseudofrin, Sudafed Decongestant 12 Hour, Sudafed Decongestant Children's Chewable, Sudafed Decongestant Extra Strength, and Triaminic Pediatric Oral Cold Drops. It is also contained in 85 other combination medications listed in the 2003 CPS! The reason Pseudoephedrine is so popular is that it is less likely than the other drugs in this class to cause anxiety, restlessness and tremor due to CNS stimulation. It has no commonly reported side effects although nervousness, dizziness or sleeplessness are listed on the packaging and are not rare. Pseudoephedrine lasts 4 to 6 hours but can also be taken as a slow release preparation that lasts 8 to 12 hours. Overdose with this medication can cause delirium, seizures, or loss of consciousness.

Xylometazoline is a long lasting decongestant (up to 10 hours) that was the sole ingredient in Otrivin (no longer available). It is still available as Decongest, a nasal spray. Xylometazoline has no common side effects. Overdose may cause headaches, insomnia, and drowsiness.

There are several general concerns with decongestants and diving. All decongestants work for only a limited period of time. If you take a decongestant and it wears off during the dive, the mucous membranes could swell and block the opening to a sinus or to the middle ear. Then, when you return to the surface at the end of the dive, you could end up with high-pressure gas trapped inside a sinus or in a middle ear. This reverse sinus squeeze or reverse ear squeeze can be EXTREMELY painful and rupture of the eardrum or even rupture of the sinus into the space around the eye or the brain is possible. I have seen one reverse sinus squeeze that required narcotic painkillers for two days before the pressure was released and the pain resolved.

Almost all medications have potential side effects that could be a problem while diving. You should take any new medication a few times when you are not diving to determine its effects on you, before you consider taking it while diving.

The most serious potential problem with the sympathomimetics and diving is that they are all to some extent CNS stimulants, especially if taken to excess. Stimulation of the CNS will greatly reduce your tolerance to high levels of oxygen, thereby increasing your risk of CNS O2 toxicity and of having a seizure while diving. Therefore, you should not take any decongestants before a dive where you expect to be exposed to an elevated pO2 (air at 99 fsw has a pO2 of 0.84 ata). The Canadian Forces limits depth to 60 fsw breathing air if Sudafed has been taken.

In spite of the fact that most decongestants are CNS stimulants, some of them will cause drowsiness in some individuals. If you add the CNS depressing effect of nitrogen narcosis to the drowsiness caused by the medication, you could suffer a far greater degree of incapacitation than you expect. Therefore, if the medications cause you to feel drowsy, you should not dive. If you do not experience drowsiness, you should still limit your exposure to narcosis by limiting the depth of your dive to 60 fsw or less (Nitrox diving depths should be limited by the pO2).

In general decongestants are fairly safe medications. Nevertheless, you should take them only if required, stop them as soon as possible, and you should consider skipping the dive if you require them. If you take a decongestant, you should limit the narcotic depth of your dive, and the pO2 exposure.