Gastrofensin AN 5 free base, a 4-phenyl-tetrahydroisoquinoline derivative, is an antiulcer agent.

Gastrofensin AN 5 effectively suppresses ulcer formation across all tested models, demonstrating significant antiulcer activity even at a low dose of 0.100 mg/kg. The effectiveness of Gastrofensin AN 5 in inhibiting ulceration enhances with dosage increments, peaking at a dose of 1 mg/kg (86.15%). Comparative analyses with Ranitidine and Cimetidine, on identical experimental gastric ulcer models, reveal that Gastrofensin AN 5's antiulcer efficacy substantially surpasses those of the aforementioned drugs.