One of the complaints we see voiced quite frequently is that "my patch runs out early." Women experience symptoms of falling estrogen or hormonal fluctuation a day or more before they are due, according to their prescription instructions, to change the patch out for a new one.
Now, we've discussed elsewhere that it's normal for the effects of our HRTs to rise, plateau, and fall again in the lifespan of a single dose. In the case of patches, that lifespan is spread over a half to a full week, depending upon the brand. But the intent of the manufacturer is that the decline should be happening just when it will cross the upward curve of the next dose, providing fairly steady hormone levels despite the changeover. So what is going wrong when it doesn't last the full specified amount of time? The clue we need is revealed when we look at just how patches work to deliver hormones to our body.
Patches (or cream or gel or ring, for that matter) work by a simple diffusion mechanism. All substances move from an area of high concentration to one of low concentration to equalize their distribution (assuming they are in a medium that allows them to move—which patch adhesive, skin, body fat and your circulatory system all do).
So you have a patch that has X amount of hormone distributed in the adhesive matrix. You have your body in which you have a lesser amount of hormone (and this is why you have to rotate patch sites, to get them on an area that is less-saturated from the last dose). The rate at which the hormone moves is related to the relative difference in levels between the supply and deficit sides. That is, the steeper the gradient, the stronger the pull and the faster it moves. Or, if this is easier to picture, the lower the level on the one side relative to the (supply) other, the faster it flows downhill.
Another variable in this movement is how rapidly it clears the recipient area—if the circulation is carrying it away quickly, the local concentration will stay low and suck the supply down more rapidly. This is why you look for consistency of fatty tissue, not muscle or bone, to put the patch on. If you place it on circulation-rich muscle one time and on circulation-poor fat the next, you'll get a very different level of clearing from the recipient site and hence experience a different dose delivery curve in the body.
Patch doses, in terms of "life of the patch," are calculated (and licensed) by the manufacturer on an average amount of deficit in a well-balanced user placing the patch on an average bit of fatty tissue with an average amount of circulation so that the amount of hormone it contains is transferred over to the tissue in the average planned lifetime of the patch.
If, however, you place it on a more efficient (in terms of clearing it through into your system) tissue or if your underlying deficit is higher than those calculated averages, you will exhaust the supply in the patch sooner than that planned lifetime between changes.
Now, remember how we said above that in the normal patch dosing curve, hormone release will rise sharply after the patch is put on, hold a peaking curve through most of the patch lifespan, and fall off towards the end? That falloff is due to this same mechanism of diffusion. At the end of the patch lifespan, the recipient site is becoming more saturated and can't clear the hormone on its way as rapidly, and the patch itself is drawing down and hormone has to be gathered from all through the matrix instead of that right up against your skin. This is all the normal physics of this delivery system, not it going awry in any way. The timing of the dose delivery curve, then, relates to the dose in the patch and the amount of hormones in the delivery area and the overall system, not some actual timing mechanism built into the patch itself.
For most women, once their systemic levels are high enough that they don't immediately suck all the hormone out of the patch, the lull towards the end is offset by the higher onset of the new patch and the reserves that remain, undiffused but slowly clearing, from the old site. If their overall supply is enough for their system to be meeting their needs, this amount of fluctuation should not be troubling (slightly noticeable, perhaps, but disabling, no).
Where women seem to be running into difficulty is when they are running in such borderline deficit all the time that they are sucking the patch dry too soon and then having more of a lull than they can cope with during that period when their needs are then going unmet. Again, it's not a matter of the patch misperforming for them—it's working fine. What the problem is more likely to be is that it's not an adequate dose for their needs and their demand is higher than that particular patch dose is calibrated to deliver.
Thus, the first response in troubleshooting "running out too soon" should probably be to question the overall dose, not the patch timing per se. Were that same woman using a slightly higher dose, one that meets her needs more fully, she might not find that she is exhausting the patch "too soon."
Does it matter whether she does this or just changes the patch more often? If she's fooling herself and her doctor by thinking that she's using a lower dose, then yes, this may be harmful in that it can cause undervaluation of risks. For example, if she is using a nominal 0.25mg weekly-change patch to limit her hormone exposure due to some hormone-related risk but she is changing it twice a week (and exhausting it fully on that interval) instead, she's in fact getting 0.5mg. That's a big difference and perhaps enough to totally rewrite her true exposure risk. If she and her doctor fail to understand this, they may even misinterpret the situation to be that she's better off using "only" the 0.25mg and changing it more often than if she were to increase to a 0.5mg. Remember: nominal patch dose is not a delivery throttle: it's only the "average" draw an "average" woman puts on it. If you're using more than that, it doesn't matter whether you get it by more dose per patch or more patches per time, you're still using more.
While some women have suggested that waiting till the patch wanes to change it provides a sort of self-regulating optimal dose, we're not sure but that keeping the body on that sort of edge may ultimately be the most stress-free level of balance. The idea of correctly-functioning patch delivery is, remember, that the end-patch dip is covered by the new-patch ramp up, maintaining a fairly steady supply. By relying on dip before changeout, then, a woman is putting herself back into fluctuation and insufficiency on a regular basis, without ever getting into a cycle, such as women on daily dosing experience, in which the body's innate caching and conversion mechanisms can cover her needs between doses. While we've seen some women invent all sorts of complicated systems of patch change, requiring cutting the patch into multiple pieces and then changing them out on a more frequent schedule in an attempt to avoid any dips, we have to question the ultimate viability of that kind of scheme. Not only is it excessively fussy (and easily confused) a system, but if they are on such a knife-edge of imbalance that they can't get a decent overlap of wax and wane, perhaps they should ask whether they might be using the wrong delivery system altogether.
And of course your insurance may be a problem even if your doctor specifies an accelerated change schedule. The fact of medication pricing is that the same dose in one vs two units has a different cost. The cost of two patchs of, say, 0.25mg is higher than the cost for one 0.5mg patch because of the additional backing, other ingredients, packaging and handling. For some women, then, this might be a make-or-break factor, and it can be useful to know that they can address the "runs out too soon" problem with a different dose rather than more patch expense.
Demystifying the mechanics of patch delivery can go a long way in troubleshooting balance problems you may be experiencing with them. Whatever solution you ultimately take is your own responsibility, but we hope that it's one that is based on fact rather than fooling yourself about the mechanisms involved.
