I came donwnwith a UTI last weekend and went to see my Doctor Monday morning - she put me on Macrobid, 100mg 2x day for 4 days. Within the first day and half the back of my thighs have gotten very sore, almost as if a muscular pain, but feels more like skin sensitivity. It is hard to sit and if I sit on a cold surface, it's uncomfortable. Most of the brining from th UTI is gone, but I an still feeling a stinging sensation and the muscle pain decsribed. I have 2 more doses of Macrobid for tonight and tomorrow morning and am not confident that will clear it up.