Hi! Yes, the headaches do occur if the colon isn't flushed while parasite cleansing.
Reason is the toxins from the dying worms released which indirectly causes the headaches. Keeping the colon cleansed and bowel movements moving through will help elimiinate this-- as well as plenty of fluids every day to flush out toxins.
As for the praziquantel, the toxins from this drug, itself, could be causing the headaches-- which is a good reason to also be colon cleansing while taking this drug.
If this is a form of anti-biotic, it is good to start taking natural probiotics to restore good bacteria back into the intestines- Chemical Antibiotics destroy good bacteria which sets you up for a new worm infestation weeks later.