Antistaminics OTC Drugs and Diving

Two of my students, who will soon be DAN members, have mentioned that they take the following drugs for allergies. May I please have your comments on these drugs.
Zirtek 10mg
Neoclarityn 5mg(desloratadine)


Thank you for your question. I believe you will find the below abstract for Alert Diver useful. However it should always be remembered that, most of the times, it is the condition and not only the drug for which it is used, to be the real potential contraindication to diving.

From Alert Diver II/1999
Taking Drugs When you Dive? If You're Using Any Medication, Make Sure You're Informed About Drugs and Diving Before You Take the Plunge. By Bryan G. Levano, M.S., R.Ph.

At times divers may experience some form of discomfort - dizziness, diarrhea, an upset stomach, nasal congestion, headache - which can interfere with the enjoyment of a dive. Over-the-counter products (OTCs) are often the most immediate source of relief available to them. OTCs are medications designated as safe for the short-term treatment of ailments that can be self-diagnosed by the consumer. However, with literally hundreds of products available to consumers, the choice of the best agent is often a difficult one. The active ingredient available in a manufacturer's proprietary product may also be in many other preparations as well.
To add to the confusion, many products combine two or more agents to relieve multiple symptoms, as we often see on cold and allergy products. The most common OTCs - and of greatest interest for recreational divers - fall within the following categories: - Antihistamines; - Decongestants; - Anti-motion sickness preparations; and - Analgesics and anti-inflammatory agents.

ANTIHISTAMINES Allergic Rhinitis
In 10 to 15 percent of the U.S western world population, the immune system becomes sensitized to airborne allergens, such as dust, pollen and molds. The result is a heightened response known as allergic rhinitis or as seasonal allergies and hay fever. The allergen or foreign substance triggers a response by the immune system directed at isolating and ridding the body of this substance - an allergic reaction.
Major contributors to allergies are the mast cells, the predominant storage site of histamine in the body. Mast cells are found in great abundance in the skin, the bronchial tree and intestinal mucosa. During an allergic response, these mast cells release histamine and other immune system modulators, which in turn bring on the symptoms associated with allergies - runny nose, congestion, sneezing, itchiness, tearing of the eyes, and a cough with post-nasal drip.

Treatment: Antihistamines are drugs that weaken the allergic response by blocking the effects of histamine. They can be used before or after an allergy attack has begun. Although they can modify an allergic response, antihistamines are not without drawbacks in the form of side effects. The most common side effects include: drowsiness, dry mouth, blurred vision, urinary retention and increased heart rate. Drowsiness, one of the more troublesome side effects to divers, occurs because of the drug's effect on the brain. Additionally, drowsiness can be heightened by nitrogen narcosis, putting a diver at greater risk. Note: It is important to recognize that all individuals react differently to medication. When trying a new medication, begin taking it in an environment where unwanted or unexpected side effects will not be a problem. Only after verifying that no undesirable effects occur should you take the drug when participating in activities that require alertness, such as scuba diving. Since one of the actions of antihistamines is to reduce secretions (tearing, runny nose), dry mouth can be another bothersome side effect. This can be made worse by breathing through a regulator. Making sure you are adequately hydrated during the dive trip can lessen this effect. Sucking on hard candy between dives can increase salivation and provide some temporary relief, and saline mist sprays can alleviate nasal dryness as well.
New Non-Sedating Agents. In the late 1980s, a second generation of non-sedating, longer-lasting antihistamines became available. These agents, such as loratidine (Claritin), cetirizine (Zyrtec) and fexofenadine (Allegra), are available by prescription only. Some nasal sprays are available for congestion related to allergies. Recently, cromolyn sodium (Nasalcrom) has been made available as an OTC product. Though not an antihistamine, non-sedating Cromolyn works by stabilizing mast cells: i.e., it prevents the release of histamine. Since its action is limited to these specific cells, it does not have the side effects associated with antihistamines. Cromolyn sodium only works by preventing allergic attacks, however, so it must be taken prior to exposure to the allergen.

Sinus Congestion, Treatment. The drugs used to treat congestion are called sympathomimetic agents, and may stimulate the release of norepinephrine. This causes blood vessels in the nose to shrink, and it reduces any swelling there. The major side effect of these drugs is their ability to increase heart rate and blood pressure. These agents usually have a short duration of action - about four to six hours - and may wear off during a dive, causing a rebound effect and a reverse squeeze on ascent. Divers concerned about drugs with systemic side effects may choose topical nasal sprays to avoid the jitteriness and rapid heart rate seen with other sympathomimetics. Some of these sprays even have an extended action (8-12 hours). The drawback, however, is that these agents should not be used for more than three days at a time: tachyphylaxis (rapid drug resistance) occurs, requiring an increased amount of the drug to be effective. Saline mist sprays are another option for those concerned with drug side effects. They may be used as often as necessary and will not result in tachyphylaxis. Pseudoephedrine, a key ingredient in Sudafed, is a commonly used decongestant by divers. A recent study highlighted its effectiveness. The study compared pseudoephedrine to a placebo in its ability to prevent middle ear squeeze in novice divers. It concluded that a 60-milligram dose of pseudoephedrine administered 30 minutes before the dive was effective. This study was conducted to a depth of 40 feet / 12 meters, with objective data gathered only through otologic (ear) exams. Symptoms of side effects were collected in a questionnaire.

Treatment. Unfortunately, once it occurs, motion sickness can seldom be treated with medication; anti-emetics must be taken prior to embarking on a boat. OTC anti-emetics are all a subset of the antihistamines, and these medications have a greater ability to cross into the brain. Because of this, however, they also have a greater sedative property, which can be a problem during diving. This is particularly true when combining medications to treat both allergies and vertigo. Many people who suffer from motion sickness are familiar with the scopolamine patch (Transderm Scopr), an effective preventative to motion sickness. The patch must be applied at least four hours prior to exposure to motion. Its side effects may present problems for divers - namely, drowsiness and mental confusion, although these effects are usually minor.
Transderm Scop: 'The Patch' for Divers, by Edward D. Thalmann, M.D.
The policy of the Navy Experimental Diving Unit ( NEDU) is that before issuing this drug, the diver had to place the patch and wear it 24 hours on dry land and then be interviewed by one of the Diving Medical Officers to ensure there were no undesirable side effects before diving. The patch had then to be placed four hours before leaving shore, but once in place, it could be worn even while diving. The only problem was, that since it was placed behind an ear, it would sometimes fall off without being noticed until that queasy feeling set in. Before it could be decided to recommend it for general use in Navy divers, the US Navy performed a study where divers on a 18-msw air saturation dive that lasted five days were each given a patch containing either the scopolamine or a placebo. It was a blinded study - that is, none of the diver subjects knew which patch they received. Divers performed psychomotor studies several times during the dive and were also asked to write down anything that occurred throughout the day that they thought might be a side effect. Basically, there was no difference between the two groups, so it was concluded that modest hyperbaric exposures would not increase the probability of side effects or adversely affect performance within the normal scuba diving depth range. Transderm Scopis recommended in the U.S. Navy Diving Manual (paragraph 8-8). However, certain people do suffer side effects which would make it inappropriate for them. You need to have it prescribed by a physician, and you should test it before diving. Wear a patch for at least 24 hours on dry land in a situation where the potential side effects will not cause harm. If no side effects occur, then try it out on a dive. Make sure you apply the patch to thoroughly clean and dry skin so it won't fall off.
Non-Drug Therapy. There are non-drug therapies for vertigo that have met with varying success. Among these are Seabands and Travelaides. These remedies work according to acupressure principles via stimulation of the Neiguan point, located three finger breadths from the wrist joint on the inner arm, between the two central flexor tendons. The person using Seabands or Travelaides wears specially made elastic bands around the wrist. A plastic dome is attached to the bands, pressing on the acupressure point. Some users have suggested that these bands can stop nausea, even after it has started.

Oral OTC pain relievers are found in three categories: Acetaminophen , Salicylates (such as aspirin) and Non-steroidal anti-inflammatory drugs (NSAIDs). When injury occurs, the body produces prostaglandins, active, multifunctional substances that have actions throughout the body. They have important actions in mediating inflammation (edema, redness) and pain. The salycilates and NSAIDs inhibit the production of the prostaglandins, which alleviates pain and reduces swelling. The NSAIDs have seen a recent boom since they have been moved from prescription-to OTC-status drugs. Acetaminophen also helps in reducing pain but is not as effective as salycilates and NSAIDs as an anti-inflammatory drug. The most significant side effects of the salicylates and NSAIDs is an upset stomach and gastrointestinal ulceration. High doses of aspirin can cause tinnitis, or ringing of the ears, and may also produce bleeding problems. Some people report drowsiness occurring with ibuprofen, but this is uncommon.
Besides these drawbacks, the reason for needing painkillers may affect fitness to dive. An injury, however medicated, can affect the full range of motion and increase the risk of the dive. Also, the effects of pressure on an inflamed tissue are unknown. As an added caution, medication may obscure the signs and symptoms of decompression illness.

Many people are not aware that some drugs can increase the skin's sensitivity to sunlight (ultraviolet A (UVA) and ultraviolet B (UVB) radiation )and cause either photoallergies or phototoxicity. A photoallergic reaction occurs when ultraviolet light alters the structure of the drug, in a way that may stimulate an allergic skin reaction appearing as an eczema-like condition that can spread to areas not exposed to the ultraviolet light. Phototoxicity is more common: it is not an allergic reaction, instead, the drug absorbs the UV light and releases the energy into the skin, causing local cell damage. Both reactions can occur immediately or have a delayed onset. How can you protect yourself from the sun when you're on medications? The best advice is to avoid or limit your exposure to the sun whenever possible. Sunscreens can offer some protection. Most sunscreens will block only UVB light, however, and it is UVA light that is often implicated in these reactions. Titanium dioxide can block both the UVA and UVB. Try to avoid sunscreens containing bergamot oil, sandalwood oil, benzophenones, PABA, cinnamates, salicylates, anthanilates, PSBA, mexenone and oxybenzone. These ingredients themselves can elicit a photosensitivity reaction.

I would like to offer a word of caution about a group of products often overlooked by healthcare providers - natural products. It is unknown how most of these agents interact with each other, with other drugs or with the body when under pressure. Be vigilant in tracking the effects of the medications and supplements you are taking, particularly those new to you. If you have questions, consult your doctor or pharmacist.



Before using any medication during the dive, try it out beforehand to familiarize yourself with its effects. This is especially true of drugs that have noted side effects like drowsiness. In order to make a proper decision, you must have all the facts available. Talk to your doctor, or call DAN's Dive Safety and Medical Information Line with questions. During our open-water diving classes we all heard that drugs and diving just don't mix: this advice stems from the fact that the effects of pressure on the pharmacodynamics of drugs deserve more study. Remember that diving is fun, but missing a day's diving is better than spoiling an entire trip or putting yourself and your buddy at risk.