Try stay away from the ones with high sugar content. Ibuprofen is fine as the sugar coating is negligible.
When I had my cold I used cough mixture and still lost that week but less than normal. Remember if you are getting sick you might want to up your intake as your body fights the infection so will need more energy. Just be sensible and listen to what it is telling you.
I agree with sunflowerlady. If you're feeling really poorly, it might be best to up your calorie intake. Also if you really need the medicine, it's best to just take it. I hope you feel better soon This diet is hard enough without feeling poorly xxx