The Ministry of Health is warning people not to take six medicines that have been on sale at a supermarket selling mainly Chinese goods in South Auckland.
The products range from penile erection capsules to children's cough syrup.
They have not been approved for the New Zealand market because they are prescription or pharmacy-only medicines.
The medicines range from products containing the potent anti-inflammatory piroxicam, an antihistamine and cough suppressants.
Medsafe compliance team leader Derek Fitzgerald said the penile erection capsule contains sildenafil, which is potentially fatal to some people.
He said the substance can interfere with heart medications and men with certain heart conditions should not take it.
Mr Fitzgerald said it is possible other Chinese goods retailers around the country could be stocking the medicines.
Medicines not approved
Santi Scalper Penis Erection Capsules (Santi Nui Ban)
Lufen Huang Min Pian
Madame Pearl's Cough Syrup
Madame Pearl's Cough Syrup (for Children)