Paperwork could be costing the NHS millions of pounds because it is too complicated to claim costs for cancer drugs, research has shown.
Health trusts have started sharing the cost of expensive treatments with pharmaceutical companies, but up to 50% of costs are not reimbursed, according to a survey of 31 English health trusts.
Although wider access to cancer drugs is clearly important, one researcher said over-complicated reclaim systems could threaten such schemes' viability.
Steve Williamson, consultant pharmacist at Northumbria Healthcare NHS Foundation Trust, wrote in Clinical Pharmacist that pharmaceutical firms put pressure on the NHS to track patients and complete a series of forms by specific deadlines.
Researchers asked pharmacists about refund given for four of the first "patient access schemes", which include kidney cancer drug sunitinib, which has a first free cycle followed by a discount, and bortezomib for multiple myeloma, where the NHS can claim a refund if the drug is ineffective.
But it was found up to 50% of entitled refunds may not have been received for cases of these two medications.
The Department of Health said it was working to simplify the schemes. A spokesman said: "Primary care trusts and hospital trusts need to agree locally between them how any rebates paid by drug companies are dealt with."