Vested interests have been accused of trying to thwart attempts by hospitals to have cheaper generic drugs prescribed to patients.
The Minister of State for Health, Mr Tim O'Malley, pointed to the vested interests as hospital consultants, non-consultant hospital doctors and drug companies.
He said yesterday that doctors were often "wined and dined" by drug companies and then asked to prescribe certain drugs not on a list decided by the hospital's therapeutics committee.
"No undue pressure should be put on doctors to prescribe drugs and doctors should use their clinical judgment only, at all times," he said. "Some pharmaceutical companies are very ethical but the marketing divisions of some others leaves a lot to be desired."
Mr O'Malley said prescribing more expensive drugs when generic drugs would suffice was costing the State significant and unnecessary sums every year.
He urged hospital pharmacists to play a greater role in ensuring that drugs administered in hospitals were chosen "on the twin basis of cost and efficiency".
"As a pharmacist and as a government minister, I think it is incumbent on the profession and on the public to demand the best possible service and the best possible value for money," he said.
Furthermore, he said, tried and trusted drugs should always be used as a first line of attack before new and more expensive alternatives new on the market.
The general secretary of the Irish Hospital Consultants Association, Mr Finbar Fitzpatrick, said it was the job of consultants to prescribe the most medically effective and cost-efficient drugs.
"Many of the more modern drugs are the most effective medically but they are also the most expensive," he said.
He admitted many medical events and research projects were funded by drug companies but he was absolutely satisfied this did not influence prescribing patterns. "In an age when litigation is rife, doctors would not take any chances with prescribing anything other than something medically appropriate for a patient," he added.