Will doxycycline (always) exacerbate existing increased icp? and will it do so immediately?

I don't believe that the accurate incidence of elevated ICP in users of doxy is known, but studies have shown that if it occurs it will develop within 8 weeks. In one case report, a person on the acne medication, retinA, elevated ICP developed after one dose of tetracycline, which is the class of antibiotics doxy belongs to. This combination of meds must be avoided.

A number of antibiotics and even Vitamin A have been implicated as causing Benign Intracranial Hypertension, (Pseudotumor Cerebri), but often, endocrinological abnormalities have played a more impactful role. Not clear that, in presence of Pseudotumor, doxycycline would worsen, but suggest alternative antibiotic to be completely safe.