I'm on a 2x a day, 7 days round of doxycycline. i threw up 40 minutes after taking my 7th dose, did this mess up my round of antibiotics?

One dose: If you only missed one dose, there is not a big problem if you resumed your medication. If you vomited more than one hour after taking it,there is a good chance that some absorption of the doxy took place.

Doxycycline & emesis: If it is one dose after 40 minute there may have been some absorption ( about 1/2-2/3). i would just continue on to the next dose in 12 hours. if you continually vomit after doxycycline let your doctor know as a different antibiotic may be in order. http://www.drugs.com/pro/doxycycline.html

Not likely: Please take your doses after eating to minimize the nausea and emesis.