I have been prescribed and have taken hydrocodone-homatropine syrmor with synthroid. My Dr. prescribed this for me when I had bronchitis and he was fully aware that I take synthroid. I have had no problems at all from taking it. In fact, it is the only thing that worked to stop my night time coughing fits and allowed me to get the rest I needed.
Nausea, stomach upset, loss of appetite, tiredness, drowsiness, weakness, dry mouth or headache may occur the first several days as your body adjusts to the medication. If these effects continue or become bothersome, inform your doctor. Notify your doctor if you develop: rapid heart rate, chest pain, nightmares, hallucinations, blurred vision, trouble urinating. Because this medication may cause drowsiness, use caution performing tasks requiring alertness. To relieve dry mouth, suck on (sugarless) hard candy or ice chips, chew (sugarless) gum, drink water or use saliva substitute. If you notice other effects not listed above, contact your doctor or pharmacist.