I Have Started Taking Sulfameth/TMP800/160MG TB As A Generic For

I have started taking Sulfameth/TMP800/160MG TB as a generic for Septra-DS800/160MG in conjuction with a prostate biopsy. (one tablet twice daily) I started taking them last Thurs (12/15)...had my biopsy yesterday and it seems like each time I take the medicine I begin to itch more and more. No rash but itching on my arms and chest. We also had a cold snap here with dry air that might be creating dry skin. I plan on calling my urologist tomorrow morning to ask him if itching is a side effect of Sulfameth/TMP. Would it be bad for me to skip tonight's dose?