Some batches of the medicine called co-codamol might be incorrect in painkiller strength, the Medicines and Healthcare products Regulatory Agency has warned.

The mistake might be due to manufacturing the pills, the MHRA said. This mistake has led to certain packets of the batch LL1701, which has an expiry date in September 2014 has 30 grams of co-codamol rather than eight grams of the medicine in one tablet.

If someone wants eight grams then it can be taken over the counter but a 30 grams pill has to be taken with prescription only.

Wockhardt UK Ltd is the manufacturer and it has said that it is recalling the batch and a warning has been issued by the MHRA to people who supply co-codamol.

A pack contains about 32 tablets and about 39,000 packs were sent for sale to wholesalers and pharmacies in December 2011.

Ian Holloway, MHRA head of the Defective Medicines Report Centre said, “If you have a packet of the affected medicine, return it to your pharmacist who will replace it. If you think you have taken the wrong strength tablet, and in the unlikely event that you feel unwell, speak to your pharmacist or GP promptly.”