Primary Care Dermatology Society executive chairman Dr Stephen Kownacki and primary care nurse practitioner Deborah Duncan were among 19 signatories of a letter to The Times, alongside hospital specialists and leading charities.
The cost of generic substitution - allowing pharmacists to switch branded drugs on prescriptions to generic alternatives - could be greater than any savings, the letter warned.
'Only the prescribing doctor or nurse knows the patient's medical history,' the letter says. 'Substitutions should never be made without their consent and awareness.'
The letter's authors recognised that there are cases where generic prescribing is appropriate, but pointed to 'clear evidence that, for some medicines, it may be dangerous'.
Last month, health minister Mike O'Brien launched a consultation on the DoH's plans for generic substitution in England. The proposals are open for comments (www.dh.gov.uk) until 30 March 2010.