reduction in amount consumed is less than the proportional increase in the price. This effect is known as price elasticity: the drug is a price inelastic commodity, and the reduction in total amount spent is price elastic. (In contrast, commodities that are price elastic show proportionally equal or larger reductions in consumption as prices rise.) In the context of immunotherapies, although there is little reason to think that attempts to swamp or override treatment will lead to increases in the amount of the drug reaching the brain—since it is only the effective price of getting drugs into the brain not the actual price paid by a user to the drug seller that increases—increased spending implies increased purchasing from the seller. That is, if demand for the drug behaves as if it were inelastic in response to immunotherapy-induced increases in the effective price, there would be increased demand for drug purchases. It is not now known which drugs have elastic or inelastic demand. Originally, it was presumed that demand was probably inelastic. More recent evidence suggests that for some substances demand may be elastic, although the evidence base for this assertion is thin (see Chaloupka and Pacula, 2000, for a review).

The potential problems from user’s seeking to override or swamp immunotherapies and sustained-release formulations are varied. Future studies may find it productive to differentiate among use-driven harms related to the drug’s reaching the brain (e.g., many behavioral effects) or reaching other body parts (e.g., the heart or placenta) and those associated with drug ingestion or administration itself (e.g., risks of injection). Traditional forms of treatment generally affect all three types of harms proportionally, but immunotherapies, in contrast, can be expected to influence each category to a different degree and, indeed, could reduce some while increasing others. It is not clear if these new therapies protect other body parts as well as, better than, or less well than they protect the brain. Indeed, the answer may be medication-, organ-, or drug-specific, or some combination of the three.

One major concern with attempts to override the blockade effects of immunotherapy and depot medications is the risk of accidental overdose, because the level of medication effect is expected to wane over time following administration. Because there is no obvious signal to the patient that the blocking effects of an immunotherapy or depot medication have diminished after weeks or months of sustained blockade, toward the end of the effective duration of a medication dose a patient may ingest a relatively large amount of drug that had produced no overdose while the medication was more effective (more proximal to medication administration), resulting in an overdose.

Some harm stems from behaviors associated with drug use itself. Those potential harms would be exacerbated if users sought to override immunotherapies’ partial blocking by taking more of the drug. Two



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