Smooth Release vs. Extended Release Minoxidil: What's the Difference?

Why the shape of the curve matters

Swallow a standard 5 mg immediate release minoxidil tablet and the whole dose hits your bloodstream incredibly quickly. Published pharmacokinetics put the peak around 37 nanograms per milliliter (ng/mL), at about 30 minutes after dosing. Published work also puts the threshold for a measurable hemodynamic response (blood pressure and heart rate effects) at 21.7 ng/mL.

A standard Minoxidil tablet spends its first hours above the 21.7 ng/mL line you'd rather stay under, then spends the rest of the day near 0 ng/mL. Patients get the side-effect window up front and less Minoxidil coverage later. That shape is a delivery problem. The Minoxidil molecule has been generic for decades. What we care about is the curve. This post shows our measured and modeled PK, along with what the two-subject pilot can't tell us.

What "extended release" is for

Extended release is a family of techniques for slowing a drug's exit from its dosage form. There are a plethora of extended release platforms. Polymer matrices that swell into a gel and let the drug diffuse out. Lipid matrices that force the digestive system to slowly erode molecules surrounding the drug. Coatings that delay release until further down the gut. Pharmaceutical science has used these tools for half a century, across hundreds of drugs.

Built to lower the peak

Built to extend coverage

Built to time or place the dose

*MINX may also fall in the Built to extend coverage strategy. Read more about Minoxidil's open questions with regards to enzymatic conversion to Minoxidil Sulfate, its active form, and resultant theories for why smooth release Minoxidil may result in more hair growth.

All extended release products trade the same thing: a lower, later peak in exchange for a longer tail. What differs is the exact shape of the curve, which is contingent on why a formulator would want to pursue extended release. There are two thresholds often designed around in extended-release pharmacology: a safety threshold ('Built to lower the peak') and an efficacy threshold ('Built to extend coverage'). The design target is either keeping blood levels of the drug above the efficacy threshold, which matters most when the body clears the drug quickly, or keeping peak drug exposure below the safety threshold, which matters most when a drug has acute side effects.

What we mean by "smooth release"

Both the safety and efficacy thresholds have numbers attached for Minoxidil. Hemodynamic effects begin at 21.7 ng/mL. At the other end, the lowest Minoxidil blood concentration at which hair growth has actually been measured is about 1.6 ng/mL. That gives us a relatively wide window to aim at, with plenty of tools at our disposal.

A 5 mg immediate-release tablet clears the 21.7 ng/mL top of that window within the hour and is most of the way out of the system just a few hours later. Smooth release is our name for the opposite shape: get above the bottom of the window, stay far under the top of it, and hold that position for hours and hours.

MINX is an oral minoxidil capsule built around a lipid matrix, compounded on a per-prescription basis under section 503A. The drug is dispersed in lipids that erode and digest gradually, which was chosen to achieve as close to zero-order release as possible. Release rides the body's own fat-processing machinery.

We ran dissolution testing in the lab first. Then, our co-founders took it themselves and drew our own blood on a sampling schedule. In the fed test, minoxidil levels were still climbing when sampling ended at hour eight. Our model, fit to the observed points, puts the peak around 6.5 ng/mL somewhere in hours nine to ten: inside the window, against 37 ng/mL for the immediate-release tablet, and about eight hours later.

Here is what that does and does not establish. Two people is a pilot, and the peak stays labeled as modeled everywhere it appears. We measured the climb. We never measured the fall, because sampling stopped before the curve turned over. Frankly, we didn't expect it to still be rising at hour 8. What the observed data does show is less ambiguous: a low curve, still rising at hour eight, sitting inside the window for every hour we watched.

All of this data is open. We published it rather than asking you to trust adjectives.

Why a lipid matrix

We chose lipids over the more common polymer-gel route for reasons specific to what MINX is:

Fed-state behavior helps the design. Lipid excipients digest along with dietary fat. When taken with food, the matrix should process the way the design assumes.

The release mechanism is gradual by construction. Erosion and digestion of the lipid phase meter the drug out over many hours: a long, flat curve, built with delivery techniques the field has used for decades.

It suits per-prescription compounding. A 503A pharmacy compounds each prescription individually. Lipid matrices are well suited to per-prescription compounding without industrial tableting equipment.

This is a fit-for-purpose choice for a compounded Minoxidil product, and the blood-level data is the referee we submit to.

"If it releases that slowly, does all the minoxidil actually release?"

We get this more than any other question, and it usually contains three separate concerns worth pulling apart.

The first is whether the drug leaves the capsule at all. That is what dissolution testing measures, and it is the easy one: in our in-vitro work the matrix releases its minoxidil across the extended window rather than trapping it.

The second is about absorption rather than release, and for this particular drug it turns out to be a small worry. Minoxidil is at least 90% absorbed from the gastrointestinal tract according to its own FDA label, and the older pharmacology literature puts it closer to 95%, in tablet form or in solution. A molecule that well absorbed crosses membranes readily wherever it happens to be released, which is not true of everything people put into extended-release formulations.

The third question is the one nobody can answer, for any oral minoxidil product: how much of the minoxidil is turned into minoxidil sulfate. Minoxidil is converted into minoxidil sulfate inside the liver and the follicle by an enzyme whose activity varies from person to person. Due to its incredible instability, minoxidil sulfate has not been quantified in human serum by any study to date. It's a study to be run in the future. Everyone selling oral minoxidil is working with the same gap.

In the fed test, modeled total absorption came out the same as immediate release. Same drug in, a 6.5 ng/mL peak around hour 9 instead of 37 ng/mL at 30 minutes.

Where this leaves you

If you and your physician are considering oral minoxidil, the shape question is worth asking about any form you consider: where does the peak land, when, and how does that affect my experience as a patient?

MINX is a 503A compounded formulation, available by prescription, and is not an FDA-approved drug. Talk to a physician before starting or changing any treatment, especially if you have any history of cardiovascular disease. Everything referenced here, the dissolution work, the pilot data, and the model, is published in the open.