I've asked to come off Sitagliptin after having used it for 18 months. I have had headaches, upper respiratory infections non-stop, lost my voice countless times (not good for a teacher but kids love it!), choking on phlegm build-up, persistent coughing, constipation, excruciating joint and muscle pains and back and lumber pain too. But didn't put two and two together until I thought I would revisit the side effects of the meds I use - All of the above were in the sitagliptin leaflet.
So now I'm trying a week off them to see how I go but DSN feels I will need to go onto something else as BGs are too high normally. I have been on Metformin and SR version - that's another long story of pain! and Glimepiride (too sensitive).
So back to the drawing board - hope it helps!