by ecancer reporter Clare Sansom

Healthcare budgets are stretched almost everywhere, and reducing waste in healthcare spending is considered to be a very high priority.

Until now, however, one important contribution to this waste has been neglected: the mismatch between the quantities of packaged drugs available and the optimum calculated doses that can lead to more drug being supplied than used.

Drug that is left over from a particular patient is rarely re-used and must still be paid for.

This is a particular problem with those drugs for which doses are calculated based on each patient’s body size, expressed either in mg/kg or in mg/m2 body surface area.

Cancer drugs, which are among the more expensive drug treatments, often have narrow therapeutic windows and so must be prescribed in this way.

A group of researchers and pharmacists led by Peter Bach of the Memorial Sloan Kettering Cancer Center, New York, USA has now explored the extent of this problem in the US by analysing spending on cancer drugs that are packaged in single-dose vials and prescribed based on patient body size.

Bach and his co-workers selected the top 20 cancer drugs by US sales value with both these characteristics and calculated the amount and cost of each drug that would have been left over in the calendar year 2016.

The calculation methodology involved applying each drug to a ‘pseudo cohort’ of patients with representative body characteristics derived from the National Health and Nutrition Examination Survey and with diagnoses weighted by the age and race profile of each cancer type.

For each ‘pseudo patient’ the quantity of drug for a valid dose was removed from the vial sizes available for that drug and the remainder allocated to waste.

The extent of vial sharing – the relatively rare practice of using drug left over from one patient to treat the next – was estimated from Medicare records, and that amount subtracted from the total amount of leftover drug.

The findings are published in BMJ.

The amount and value of leftover drug of each type varied according to its market size, its cost per vial and the range of vial sizes available.

The proportion of drug left over was found to vary between 1% (for bendamustine) and 33% (for carfilzomib), but as some of the drugs were very expensive even small proportions in percentage terms often amounted to large dollar amounts of wastage.

For example, a single dose of the antibody ipilumumab costs $29 000 at Medicare rates, so the average wastage of 7% means that the company earns $2000 from wasted drug on each vial sold.

The amount of drug left over from dosing an ‘average’ patient with each drug varies according to the number of different sized vials provided by its manufacturer.

For example, the leukaemia drug bendamustine is supplied in four vial sizes that can be combined to form almost every dose in the range of 110 – 310 mg that is regularly prescribed for the adult patient population.

In contrast, bortezomib, which is prescribed for multiple myeloma, is only available in the US in one vial size (3.5 mg) and this is much larger than the dose of 2.5 mg that is needed for an average adult patient.

About 30% of bortezomib prescribed for US-based myeloma patients is therefore not used.

Changing vial sizes so more surplus drug is supplied can greatly increase the revenue and therefore the profit that the company makes on each dose.

The researchers made some recommendations for policy-makers that could reduce the waste derived from prescribing drugs that are unused.

Currently, FDA regulations related to this issue are ambiguous and may be unhelpful; companies are asked to supply drug in quantities that minimise leftover drug, but also to prioritise vial sizes that provide sufficient for a single dose.

Sharing unused drug between patients is recommended by the Centers for Medicare and Medicaid Services, but the CDC regards this practice as unsafe.

It would be possible for regulators to require companies to offer drug vials in a larger number of sizes designed to minimise wastage.
Alternatively, manufacturers might be required to refund the cost of leftover drugs.

Any solution would require all regulatory agencies involved to work together to reconcile views on, for example, the benefits and drawbacks of vial sharing.

If this can be achieved, however, it would offer a rare opportunity to radically reduce waste medicines, and consequently to substantially reduce their cost.

Reference

1. Bach, P.B., Conti, R.M., Muller, R.J, Schnorr, G.C and Saltz, L.B. (2016). Overspending driven by oversized single dose vials of cancer drugs. BMJ 352, i788. doi: 10.1136/bmj.i788