The number of suspicious packages stopped at the New Zealand border during a worldwide crackdown on dodgy prescription medicines has doubled.
Medsafe is now warning people about the dangers of buying medicines from overseas websites as they can be substandard, illegal or counterfeits.
The quality, safety and effectiveness of medicines bought online can't be guaranteed, compliance management manager Derek Fitzgerald said.
Prescription medicines are potent substances and should be used only after consultation with a doctor.
Anyone who still intends to buy prescription medicines via the internet should speak to their doctor about potential side effects, interactions with other medicines and appropriate dosage.
The week-long Operation Pangea VI, led by Interpol, led to 298 packages being held for further investigation by Customs and Medsafe.
This was more than double the 124 packages held during the same operation last year.
These parcels originated from 32 different countries, compared with 21 last year, and were stopped because they contained prescription medicines, weren't labelled or were known to contain undeclared or hidden ingredients.
The most common source countries were India (79), the United States (59) and China (30).
Fitzgerald said unlabelled medicines were the most prevalent products examined by Medsafe, including 8774 individual tablets.
Medicines for weight loss, diabetes and insomnia were the next most prevalent, he said.
Only one parcel contained a counterfeit or fake product - the same as last year.
This is the sixth time New Zealand authorities have participated in the operation, which ended on Tuesday and involved 99 countries.
Customs targets all incoming international mail suspected to contain medicines, and thousands of interceptions are referred to Medsafe each year.
Prescription medicines are referred to Medsafe by Customs to ensure compliance with New Zealand law.
Most prescription medicines Medsafe detains are held until the importer provides a valid doctor's prescription. If this does not occur they are destroyed.
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