Given the most logical and useful interpretation for an academic paper, I will assume you meant: — i.e., fraudulent or unproven medical remedies sold by quacks.
Based on phonetic and contextual similarity, the most probable intended term is — a colloquial abbreviation for “quack preparation” (a fake or fraudulent medical remedy) or a “quack prep school” (a low-quality educational program). Alternatively, it might be a typo of “quack peer” or “quack precept.” quack prepe