Over-the-Counter Medications

By definition, over-the-counter (OTC) medications are the classification of drugs considered safe for consumer use based solely on their labeling. When used as directed, they present a minimum risk and a greater margin of safety than prescription drugs. They are typically used to treat illnesses that can be easily recognized by the user. Additionally, there are about 300,000 OTC medications currently on the market, far outnumbering the 65,000 prescription drugs.

The fact that these drugs are readily available carries with it a sometimes faulty assumption that all OTC medications are entirely safe, whether you’re topside or underwater. All medications are capable of producing side effects.

There is little research on the effects of drugs used in a hyperbaric environment, such as underwater. Diving while using most medications is a matter for you and your doctor to discuss before you dive.

OTC Categories

Three-fifths of the medications purchased in the U.S. are nonprescription over-the-counter medications. The most commonly encountered OTCs — and those of greatest concern for a sport or recreational diver — fall within the following categories:

  • Antihistamines
  • Decongestants and cough suppressants
  • Anti-inflammatory agents
  • Analgesics
  • Motion sickness medication

Underlying Condition

A diver considering the use of any medication should first consider the underlying need or reason to take the drug. Does it disqualify you from diving, or does it compromise your general safety and that of other divers?

For example, if you need decongestants to equalize your ears and sinuses, you have an increased risk of serious injury from barotrauma. A seasick diver, medicated or not, may experience in-water disorientation, vomiting, loss of buoyancy control, and embolism as a result of breath-holding or violent diaphragm movement.

No drug is completely safe, regardless of the environment. Drugs are chemicals that alter body functions through their therapeutic action. Any medication could have undesirable effects that vary by the individual or with the environment, with sometimes unpredictable results.

Medication Classes


Antihistamines can provide relief of the symptoms of allergies, colds and motion sickness. The active ingredients include diphenhydramine hydrochloride, triprolidine hydrochloride and chlorpheniramine maleate.

In therapeutic doses, side effects may include dryness of the mouth, nose and throat, visual disturbances, drowsiness, sedation or depression. These factors can, together or separately, can affect the safety of a dive. Antihistamines can also depress the central nervous system (CNS) and impair a diver’s ability to think clearly and react appropriately.


These drugs cause narrowing of the blood vessels, which often gives a temporary improvement of the nasal airways. Common active ingredients include pseudoephedrine hydrochloride and phenylpropanolamine hydrochloride. Decongestants may cause mild CNS stimulation and side effects such as nervousness, excitability, restlessness, dizziness, weakness and a forceful or rapid heartbeat.

Medications that stimulate the central nervous system may have a significant effect on a diver. Divers with diabetes, asthma or cardiovascular disease may need to avoid using these drugs and should consult with a doctor before using them while diving.

Analgesics & Anti-Inflammatory Drugs

These medications can temporarily relieve minor aches and pains. Active ingredients include naproxen sodium and ibuprofen. Heartburn, nausea, abdominal pain, headache, dizziness and drowsiness are possible side effects. If you have heartburn, gastric ulcers, bleeding problems or asthma, your doctor may discourage you from using these medications.

Remember that even though you may be pain-free, the underlying condition is still present. Limitations in range of movement because of the injury, swelling or pain can put you at risk of additional injury. These medications may mask mild pain due to decompression illness, which can cause you to delay seeking treatment.

With analgesics or anti-inflammatory drugs, one of the most significant considerations is potential adverse drug interactions with anticoagulants, insulin and nonsteroidal anti-inflammatories (NSAIDs).

Motion Sickness Medication

Guidelines regularly prohibit the use of these medications before consulting a physician. Recreational divers should use these medications with caution.

These medications may contain meclizine hydrochloride, dimenhydrinate, diphenhydramine hydrochloride and cyclizine. Common side effects are drowsiness and fatigue, which may impair your ability to perform activities requiring mental alertness or physical coordination.

Medication Under Pressure

Any medication that affects the CNS, such as antihistamines, decongestants or motion sickness medications, has the potential to interact with increased partial pressures of nitrogen. The effects of the drug may increase your chance of nitrogen narcosis. Nitrogen may enhance the sedative or stimulant quality of the drug.

Because of the increased intensity of these effects, a new and unexpected reaction may cause a diver to panic. These side effects can vary from diver to diver, and even from day to day for the same diver. It’s impossible to predict who will have a reaction while diving.

Before You Dive

  • Many diving medicine doctors will advise that anyone who requires medication to dive should wait until the illness is over before diving rather than diving while using the medication.
  • Consult your physician when you are ill. Your doctor may be able to provide you with more effective medication and counsel you on fitness to dive.
  • Study all the information about your medication and understand the warnings, precautions and what effects it may have on your body. Starting the medication at least one or two days before diving may help you assess your reaction to the drug.

OTC Medications Reference


Active Ingredients: diphenhydramine hydrochloride, triprolidine hydrolochloride, clemastine fumarate, brompheniramine maleate, chlorpheniramine maleate, pyrilamine maleate
Common Warnings: May cause drowsiness. Do not take this product if you are taking sedatives or tranquilizers, without first consulting your doctor. Use caution when driving a motor vehicle or operating machinery. May cause excitability, especially in children. Do not take this product, unless directed by a doctor, if you have high blood pressure, heart disease, diabetes, thyroid disease, glaucoma, a breathing problem such as emphysema or difficulty in urination due to enlargement of the prostate gland.


Active Ingredients: pseudoephedrine hydrochloride, phenylpropanolamine hydrochloride, phenylephrine hydrochloride, oxymetazoline hydrochloride, naphazoline hydrochloride
Common Warnings: Do not take this product if you have high blood pressure, heart disease, diabetes, thyroid disease or difficulty in urination due to enlargement of the prostate gland except under the advice and supervision of a physician. Do not take this product if you are presently taking a prescription antihypertensive or antidepressant drug containing a monoamine oxidase inhibitor, except under the advice and supervision of a physician.

Analgesics and Anti-Inflammatory Drugs

Active Ingredients: naproxen sodium, ibuprofen, acetaminophen, aspirin, ketoprofen
Common Warnings: Do not take this product if you have stomach problems (such as heartburn, upset stomach or stomach pain) that persists or recurs, or if you have ulcers or bleeding problems, unless directed by a doctor. if you are taking a prescription drug for anticoagulation (thinning of blood), diabetes, gout or arthritis unless directed by a doctor.

Motion Sickness Medications

Active Ingredients: meclizine hydrochloride, dimenhydrinate, diphenhydramine hydrochloride, cyclizine
Common Warnings: Do not take this product if you have asthma, glaucoma, emphysema, chronic pulmonary disease, shortness of breath, difficulty in breathing or difficulty in urination due to enlargement of the prostate gland, unless directed by a doctor. Use caution when driving a motor vehicle or operating machinery. Not for frequent or prolonged use except on advice of a doctor.