Infusion suite economics: chairs, chair-turns and the drug margin question

The infusion suite is the most common way an independent ID practice converts clinical expertise into a business with real operating leverage. It is also the fastest way to convert working capital into inventory and receivables.

The capacity arithmetic

Start with the physical model, because it constrains everything else. Effective capacity is:

chairs × operating hours per day ÷ average chair time per infusion × utilisation

Two things are almost always missed. First, chair time is not infusion time: it includes access, pre-medication where required, the infusion itself, post-infusion observation and turnover. Second, utilisation is never 100% — scheduling gaps, cancellations, and the fact that infusion durations do not tile neatly into a working day all take a share.

Then apply the real constraint. Nursing ratios, not chair count, usually determine how many concurrent infusions you can safely run. A suite with eight chairs and staffing for four concurrent patients is a four-chair business with eight chairs of rent.

The drug margin question

Under a buy-and-bill model the practice acquires the drug, administers it, and bills the payer afterwards. Three exposures follow immediately:

• Working capital. You pay for inventory before you are paid for it, at a lag set by your payers' cycles.
• Payment risk. If the claim is denied — for authorisation, coverage or documentation reasons — you have already incurred the acquisition cost. For high-cost antimicrobials and biologics this is a materially different risk from a denied office visit.
• Policy risk. Medicare Part B separately payable drugs are generally reimbursed on an average sales price methodology, with payment tied to reported ASP. That relationship between acquisition cost and payment is a policy construct and it is periodically revisited.

We do not publish drug acquisition costs, ASP-based payment amounts or margin figures. They vary by drug, by purchasing arrangement, by quarter and by payer, and any number we printed would be wrong for your practice. Use your own acquisition costs and your own contracted rates in the calculator.

Build the model on more than the spread

A suite whose entire business case rests on drug margin is exposed to a single class of policy change. The more robust models also capture:

• Administration and infusion services — the professional and nursing work of delivering the therapy, coded on the infusion hierarchy.
• Facility or clinic revenue where the setting and ownership structure support it.
• Associated clinical encounters — the monitoring visits and management that accompany a course of therapy.
• Retained referrals — patients who complete therapy inside your practice rather than being exported to a competing site of care.

The four costs people underestimate

1. Pharmacist time. Sterile compounding requirements, drug storage and handling, and clinical review are not incidental. Whether you employ a pharmacist or contract the function, it is a real line item.
2. Authorisation labour. High-cost drugs mean prior authorisation on nearly every course, plus reauthorisation on extension. This is a staffed function, not a task.
3. Wastage and expiry. Inventory for a patient whose therapy changes, or a vial partially used, is a cost that the model has to carry.
4. Space and compliance build-out. Storage, refrigeration, compounding environment, emergency equipment and the accreditation or licensure your state requires.

How to test it before you commit

Run the Infusion Suite Capacity tool with your own numbers, then run it twice more: once at a materially lower utilisation than you expect, and once with the drug contribution reduced. If the project only works at optimistic utilisation and today's drug economics, you are underwriting two risks simultaneously.