China's healthcare regulator on Sunday defended the efficacy of off-patent medicines it had approved to be distributed through the country's public hospitals, saying an investigation into quality concerns had found them to be unsubstantiated.

In an interview with the state-backed People's Daily newspaper, the National Healthcare Security Administration said it performed evaluations to ensure that so-called generic drugs were consistent with the quality and efficacy of original research drugs and strictly supervised them after approval.

The NHSA launched an investigation last month after local media cited doctors in Beijing and Shanghai as saying that the cheaper generic drugs used at public hospitals did not appear to have the same efficacy or side effects as those made by Western pharmaceutical companies.

The regulator said it had looked into those claims by speaking to relevant experts as well as the heads of seven hospitals and found that perceptions that generic drugs such as anaesthetics and laxatives were less effective arose from "subjective feelings".