To the Editor: A 40-year-old, first-time traveller from the northern hemisphere, on an expedition cruise to the Antarctic Peninsula, experienced thirst, polyuria, fatigue and worsening headaches for several days before embarking on a rough Drake Passage crossing in January 2009. Being well-to-do, fit, and taking no regular medication, he had decided on an adventurous holiday rather than his usual high-end European resort vacation.

En route to the expedition vessel in Ushuaia, Argentina, the passenger hurriedly obtained a non-prescribed supply of “adventure travel” medication from a pharmacist acquaintance in the Middle East. To ensure its effectiveness, the passenger had complied with the pharmacist’s recommendation to begin taking the medication prophylactically several days before sailing.

On the outbound crossing, the passenger consulted me, the ship’s physician, about the aforementioned unusual constellation of symptoms that he had been experiencing for several days, which were now compounded by severe motion sickness.

On examination, he was not confused, had no meningeal irritation, loin percussion tenderness or fever, and was mildly dehydrated. It was soon revealed that he had been using acetazolamide for several days, as recommended.

On reflection, I thought the container for acetazolamide that he showed me bore some resemblance to the containers used to store promethazine in the ship’s clinic (similarly sized bottles with similarly coloured lids and labels), with promethazine being well recognised as an effective treatment for motion and sea sickness.1 The symptoms that he had had for several days while taking the “adventure travel” medication before embarking on the expedition vessel are ascribable to acetazolamide.2

The passenger had been given medication on the now apparent misunderstanding that it was for ameliorating symptoms associated with a “high altitude” rather than “high latitude” destination (the bottle had been dispensed after a brief conversation in English — neither party’s first language). The pharmacist had misunderstood, believing that the passenger was travelling to a destination at a high altitude, for which acetazolamide chemoprophylaxis would have been appropriate to reduce risk of high-altitude sickness.3

Polar expedition cruising remains a relatively exclusive though environmentally sensitive pursuit. In the 2008 southern summer season, 34 000 passengers departed for an Antarctic destination by ship;4 most experienced some degree of motion sickness exacted by rough passages across the Drake Passage (the “Drake Shake” rather than the much prayed for and preferred smooth crossing across the “Drake Lake”) to the Antarctic Peninsula.

Misunderstanding can occur when high latitude (the Antarctic and Arctic) is confused with high altitude, with the adventurer passenger at risk of being prescribed the wrong chemoprophylaxis. This risk may be accentuated in countries where travel medicine and pharmaceutical dispensing are not well regulated. On another note, in my opinion, it may be helpful to give medication containers and tablets a colour related to their purpose; perhaps bilious green for sea sickness and clear blue for altitude illness.