doxepin + amitriptyline

avoid combo: combo may incr. risk of serotonin syndrome, CNS depression, psychomotor impairment, altered BP, extrapyramidal symptoms, anticholinergic adverse effects (additive effects; duplicate therapy)

doxepin + perphenazine

monitor BP; consider decr. dose of one or both drugs; caution w/ high environmental temperature: combo may incr. risk of CNS depression, psychomotor impairment, extrapyramidal symptoms, hyperpyrexia, hypotension (including orthostasis), anticholinergic adverse effects (additive effects)

amoxicillin + doxycycline

caution advised if bactericidal action necessary: combo with tetracyclines may decr. penicillin antibiotic efficacy (bacteriostatic effects may decr. bactericidal action)