Good morning, @arbutus. Oh, good old Rituxan! Quite a few of us members have had Rituxan (rituximab) infusions, including myself.
It’s highly effective and doesn’t generally cause many side effects. Occasionally there can be a reaction within the first hour or two while being administered but that’s handled quickly by the infusion nurses.

You mentioned your husband is experiencing exhaustion and low blood pressure after his infusions. Both are potential side effects from the medication. If your husband is already taking medication for HBP then you should consult his doctor about altering his dosage for a while.

I found a good article for you from Chemo.com which talks about Rituxan, how it works, side effects and such.

His energy should pick up again soon. When is his next infusion?