Doctors are being warned that high daily doses of common painkillers such as ibroprofen can increase the risk of heart attack and stroke.
NSAIDs are used to treat chronic pain in conditions such as arthritis
The guidance is being issued by the Commission on Human Medicines.
British Medical Journal research published in June found taking the drugs meant an extra three people in a thousand would have such conditions.
However, the warnings do not apply to the much lower doses of ibuprofen which can be bought over-the-counter.
Millions of people take this class of drugs, called NSAIDs (non-steroidal anti-inflammatory drug), to help relieve conditions such as chronic pain and arthritis.
The drugs examined in the review were diclofenac, etodolac, ibuprofen, indomethacin, ketoprofen, ketorolac, meloxicam, nabumetone, naproxen, nimesulide and piroxicam - which is still being assessed.
The committee's recommendations have been accepted by the Medicines and Healthcare products Regulatory Agency, which oversees the safety of drugs used in the UK.
The MHRA is now to write to manufacturers of NSAIDs.
'Don't stop taking medication'
Dr June Raine, the MHRA's director of vigilance and risk management, said: "NSAIDs are important medicines and the balance of benefits and risks remains positive.
"The lowest effective doses of NSAIDs should be taken for the shortest time necessary for the control of symptoms.
"There is no need for patients to stop taking their medicines and there is no urgent need for patients to switch between NSAIDs, if they are feeling well.
"Anyone who is concerned about their treatment should talk to their doctor in the first instance."
The European Medicines Agency (EMEA), which has looked at the new evidence, has ruled that the benefits of the NSAID drugs still outweigh any increased risks.
The EMEA said: "The Committee confirmed its previous advice for doctors and patients to continue to use the lowest effective dose for the shortest possible duration to control symptoms.
"As for all medicinal products marketed in the European Union, non-selective NSAIDs are being continuously monitored, and appropriate actions will be taken if any concerns arise."
And Ellen Mason, a cardiac nurse at the British Heart Foundation said: "There has been a mounting body of evidence that taking high doses of NSAIDs increases the chances of having a heart attack.
"However, the increased risk is small, and the EMEA have concluded that it is outweighed by the benefits of pain-relief for patients with conditions such as arthritis.
"We welcome their recommendations that most people should use the lowest dose of NSAIDs for the shortest amount of time possible.
"We are pleased the EMEA will continue to review the use of NSAIDs."