Did a quick search of Doxycycline and there does seem to be problems with sleep interruption. It could be the cause of your nightmare. It doesn't seem to be a wide spread problem but with all medications seldom are all side effects reported unless they are severe. Have you had other dreams of this type and or trouble sleeping? Of course my interest is with the affect on dreams. If you have other dreams you can remember it would great if you would post them to see if there is any recognizable patterns.

Jerry

Age & Gender & Location {Required}: 63 Space Coast, Fla.

Have You Posted Before? Date of Last Post {Use Search and Your Post Name to Help Find Last Post} Male

How Did You Find the Dream Forum? Yes

Here is an article from the Psychology Today website on how some drugs affect REM sleep and can cause nightmares.
Psychopharmacology of REM Sleep and Dreams

Here is Psychology Today list of articles on dreams, dreaming and dream content Dream Catcher: The neuroscience of our night life

Jerry

Age & Gender & Location {Required}: 63 Space Coast, Fla.

Have You Posted Before? Date of Last Post {Use Search and Your Post Name to Help Find Last Post} Male

How Did You Find the Dream Forum? Yes