Hi all...52 year old male here, been suffering with IBS-D since my early 20's. Have tried all the usual meds, (bentyl, librax, etc.), all make me feel like I still need to go but can't. I was recently diagnosed with prostatitis and was put on doxycycline, 100mg. twice a day. Now normally, antibotics kill my stomach, and produce IBS attacks, but this one actually constipates me quite badly. So bad, in fact, that after three days of not going at all, I had to take dulcolax to empty out. Was wondering if I used a smaller dosage, say 20 mg twice a day, if this would be a feasible solution to my IBS-D problem. Not sure of the potential long term health risks. Any thoughts??? Thanks for your replies, and best wishes to all who are affected by IBS.