Medication & Drug Use

Dr Cecilia Roberts delves into the ever notorious topic regarding the use of medication or drugs during diving.
We receive numerous queries via the DAN-SA hotline and portal asking whether it is safe to continue diving after being prescribed certain medication or if someone can participate in a diving course whilst taking some or other tablet with a peculiar name. This can be quite a complex issue with no simple answers. One of the biggest obstacles in addressing the subject of medication or drugs in diving is that is solid data is not readily available. Most of the information that is available is taken from existing aviation or military standards, diving texts and some reputable internet resources.

A recent paper published by Dr Marguerite St Leger Dowse looks at the prevalence and type of illicit and prescribed drugs used by recreational divers in the United Kingdom. A total of 57% of respondents admitted to over-the-counter medication use within six hours prior to diving. These included mostly analgesics followed by decongestants. Another 23% of respondents use prescription medication of which 10% specified the use of cardiovascular drugs. Others medication categories included respiratory, endocrine, gastrointestinal, anti-infective, psychotropic, neurological and musculoskeletal [1]. Alarmingly, many of the drugs reported are prescribed for the treatment of medical conditions which may not be compatible with diving.
When looking at illegal recreational drug use, 22% of the respondents admitted to having used one or more illicit drugs since learning to dive, including cannabis, cocaine, ecstasy, benzodiazepines, amphetamines, LSD, heroine and “magic mushrooms”. Around 3.5% used these drugs during the last month to year prior to data collection. The use of cannabis, cocaine and ecstasy within six hours of going diving was also reported [2].
Thus, we know many divers use prescribed or over-the-counter medications and even illegal recreational substances while diving. Individual factors, existing medical and physical conditions as well as mental and physical fitness requirements for diving must be taken into consideration when addressing this topic. Diving, being subject to submersion and the resulting pressure and gas gradients, represents an important variable within which to consider the safety, effectiveness and potential side-effects of medication. Not only do drugs potentially affect diving, but there is also the interaction between diving and the medication as well as the underlying condition to consider.
Major Concerns

Some drugs affect alertness and consciousness, leading to drowsiness and sedation or even impaired cognitive function and the integration of thought and action. Some also affect neuromuscular strength and coordination. The interaction or cumulative effect of nitrogen with certain drugs like sedatives and tranquilisers can potentiate inert gas narcosis at a shallower depth than anticipated. Other drugs increase the risk of developing oxygen toxicity which can pose a bigger threat when diving with oxygen-rich gas mixes. The changes in our blood acidity (pH levels) seen due to our breathing patterns during diving and carbon dioxide level changes not only affects the metabolism of certain drugs, but can also be influenced by some drugs and be a contributing risk factor for other complications. Nitrogen narcosis or elevated carbon dioxide levels may combine with, for example, alcohol, opiates and anti-histamines to produce severe impairment of mental function. Some drugs like diuretics, alcohol or caffeine can lead to dehydration, especially in an activity like diving where dry compressed air is inhaled accompanied by tropical environments which are usually hot and humid. Our exercise tolerance or ability to do “work” underwater are also affected by certain medications like beta-blockers. Lastly, but equally important, the safety of other divers needs to be taken in consideration when evaluating drugs in the diving environment.
Drugs Under Pressure

When we look at the pharmacology of drugs we need to consider the absorption and distribution of the drug followed by its metabolism and finally, its elimination. Immersion and pressure produce certain cardiovascular changes leading to decreased perfusion of the gastrointestinal tract, liver and kidney which will affect the absorption and circulation of drugs. Depending on where the drug is metabolised in the body and the rate thereof, excretion may be affected by the fluid shifts that occur during diving. But, what about the side-effects we often see with medications? These, as well as the possible interaction with other drugs taken concomitantly, can be troublesome and require thought.

Seven Key Questions

To assist us in answering queries relating to drugs and diving, the following seven-step approach is used:
What is the drug and how does it affect the individual?

This includes the effect and side-effects the drug has on an individual as well as any drug interactions.
What is the reason for taking the drug?

For what disease or disorder is it used and how does it affect the individual? The overarching perspective is that the indication that the medication is being taken for to treat or manage it, is of more significance than the medication itself.
What kind of diving is executed in or planned?

Those involving exercise and exertion, exposure (heat and cold), elaborate equipment (technical), extreme depths or duration (decompression stops), or intricate travel logistics can complicate matters and need careful consideration.
After putting the drugs, diseases and type of diving in perspective, the following questions facilitate further evaluation:
What is the drug-disease interaction?

This includes the spectrum of effects and consequence of the drug on the disease and vice versa, especially where more than one drug is involved.
What is the drug-diving interaction?

How does the drug affect diving and what effect will the diving environment will have on the drug?
What is the diving-disease interaction?

How does the health condition affect diving performance and how will the diver be affected by the activity of diving? Is the condition compatible with the diving environment? Also consider whether there is an increased risk for diving-related illness.
How is diving safety affected?

Lastly, it is important to consider how the above factors influence the overall diving safety of the individual as well as the rest of the dive team.

The underlying condition as well as the extent of organ function are probably the most important factors of concern. Symptom control and the length of time on medication with the potential for unexpected side-effects need to be established. Lastly, the consequences of altering medication or in some cases, treatment cessation, may need to be considered. Some possible control measures may include changing to a different drug or adjusting the dosage thereof. Certain special dive procedures may need to be adopted or dive practices may need changing. In some cases, particular restrictions may need to be imposed, but unfortunately in selected cases no further diving may be advocated.
Although the issue regarding medication or drug use in the diving environment is not an easy one to approach, by following a systematic, rational approach one can formulate this “bitter pill” into a less atrocious one to swallow.
  • St Leger Dowse, M., Cridge, C. & Smerdon, G. The use of drugs by UK recreational divers: prescribed and over-the-counter medications. Diving and Hyperbaric Medicine. 2011; 41(1): p16-21.
  • St Leger Dowse, M., Shaw, S., Cridge, C. & Smerdon, G. The use of drugs by UK recreational divers: illicit drugs. Diving and Hyperbaric Medicine. 2011; 41(1): p9-15.

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