harvey,

Thanks for your question.  Of the three medications, norvasc, and to a lesser extent diovan, can cause blood vessels to dilate.  One of the known side effects of norvasc is flushing.  This factor, plus exposure to sun, can cause further dilation of blood vessels, and possibly lead to a loss of fluid within your blood stream.  This may result in dry mouth and possibly even some dizziness.  But if you generally tolerate these medications, it is unlikely that 15 minutes of sun exposure would result in your being dehydrated, but anything is possible.  People exposed to the sun and/or heat should always keep themselves hydrated, which is a good recommendation to everyone. 

Should this be a recurring problem, I suggest you discuss it with your physician for his opinion and suggestions.

Best wishes.

Martin Cane, M.D.