# L-08 — Ask what the vehicle arm did

In sixteen controlled trials now in this register, between 3% and 58% of people improved on the base cream or the placebo tablet alone. Not one compounded product sold direct to consumers has ever published that number, because not one has ever measured it.

- **Canonical:** https://www.30plusskin.care/ledger/ask-what-the-vehicle-arm-did
- **Site:** 30+/SKIN — Skincare, published as a spec sheet.
- **Issue:** ISSUE NO. 13 / REV. 2026.10
- **Standing terms:** INDEPENDENT · AFFILIATE-FUNDED · NOT MEDICAL ADVICE

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- **Published:** 2026-09-13
- **Reading time:** 5 min
- **Tags:** EVIDENCE, CONTROLS, REGISTER

Every controlled trial has two arms. One gets the drug. The other gets the identical product with the active removed, applied on the same schedule, by people attending the same appointments and following the same instructions. The second arm is the only thing that converts a result into evidence, and it is the number the consumer end of this market has never once printed.

Here is what the base alone achieved across the approved products in this register.

| Field | Value |
| --- | --- |
| ZORYVE FOAM — TREATMENT SUCCESS, 8 WEEKS | 58.0% AND 40.8% ON VEHICLE |
| EPSOLAY — IGA SUCCESS, 12 WEEKS | 20.7% AND 28.2% ON VEHICLE |
| TAZORAC — PSORIASIS SUCCESS, 12 WEEKS | 24% AND 26% ON VEHICLE |
| RENOVA — ANY IMPROVEMENT IN FINE WRINKLES, 24 WEEKS | 39% ON VEHICLE |
| RENOVA — FITZPATRICK IV–VI SUBGROUP | 43% ON VEHICLE vs 29% ON DRUG |
| FINACEA FOAM — IGA SUCCESS, 12 WEEKS | 23.4% AND 32.5% ON VEHICLE |
| SOOLANTRA — CLEAR OR ALMOST CLEAR, 12 WEEKS | 11.6% AND 18.8% ON VEHICLE |
| ALTRENO — EGSS SUCCESS, 12 WEEKS | 6.9% AND 12.5% ON VEHICLE |
| ARAZLO — EGSS SUCCESS, 12 WEEKS | 13% AND 17.3% ON VEHICLE |
| WINLEVI — IGA SUCCESS, 12 WEEKS | 8.7% AND 6.6% ON VEHICLE |
| RHOFADE — COMPOSITE SUCCESS, DAY 29 | 5% TO 9% ON VEHICLE |
| RETIN-A MICRO 0.1% — NON-INFLAMMATORY LESIONS | 22% AND 3% REDUCTION ON VEHICLE |
| ORACEA — CLEAR OR ALMOST CLEAR, 16 WEEKS | 19.4% AND 6.3% ON PLACEBO |
| MIRVASO — COMPOSITE SUCCESS, DAY 29 | 9% TO 11% ON VEHICLE |
| SEYSARA — IGA SUCCESS, 12 WEEKS | 10.5% AND 15.3% ON PLACEBO TABLET |
| KLISYRI — COMPLETE CLEARANCE, DAY 57 | 5% AND 13% ON VEHICLE |
| TRI-LUMA — COMPLETE CLEARING, 8 WEEKS | 0% TO 15% ON TWO-DRUG COMPARATORS |

The spread is enormous and it is not noise. In photoageing, nearly four people in ten improved on sunscreen, sun avoidance and a plain emollient. In rosacea, a third succeeded on foam base and instructions. In acne, the vehicle response ran from 3% to 17%. In one melasma comparator arm, nobody cleared at all.

## What the vehicle arm is actually made of

It is tempting to file this under placebo and move on. That is the wrong reading, and the Finacea trials show why. Subjects in both arms were instructed to avoid the foods and drinks that provoked their own flushing, and to stop using soaps, alcohol-containing cleansers, tinctures, astringents, abrasives and peeling agents for the duration.

> A third of the rosacea vehicle group succeeded on trigger avoidance, stopping their irritants, and applying a bland base twice a day. That is not placebo. That is treatment.

Renova's vehicle arm is the same story in a different condition. Every subject in every arm was on a comprehensive skin care and sunlight avoidance programme including sunscreen, protective clothing and a non-prescription emollient. Thirty-nine per cent improved on that alone, and the label says so in the indication section itself.

So the vehicle arm bundles four things: the base cream, the behavioural instructions, the removal of whatever the person was doing before, and the attention of being in a trial. Three of those four are free.

## Why nobody selling direct will ever show you one

Running a vehicle-controlled trial means manufacturing an identical inactive product, recruiting hundreds of people, randomising them, blinding the assessors and accepting in advance that the answer might be small. It costs millions and it can embarrass you. Nothing requires a compounding pharmacy to do it, and no compounded product in this register has.

What appears instead is the day-30 satisfaction survey: 74%, 79%, 80%, 81%, 88%, 90%, 91%. Uncontrolled, unblinded, self-assessed, by paying subscribers, at a timepoint before most of these drugs have finished working. Those figures are not lies. They are measurements of a different thing — how people who bought something feel about it a month later — presented in the visual grammar of a clinical result.

The comparison that makes the point is Tri-Luma. Investigator-assessed complete clearing of melasma at eight weeks: 38% in the better trial, 13% in the other. Compounded melasma products advertising 74% to 91% are not outperforming it. They are not measuring the same thing, and one of them has a control arm.

**THE ARITHMETIC IN PRACTICE**

- [R-34 Bausch Health Renova](/reviews/renova-tretinoin-cream-002-review) — CONDITIONAL 72/100 — 39% improved on vehicle; the drug reached 60%. The gap is the drug.
- [R-42 LEO Pharma Finacea Foam](/reviews/finacea-foam-azelaic-acid-review) — RECOMMENDED 81/100 — Vehicle arms at 23.4% and 32.5%, achieved largely by trigger avoidance.
- [R-39 Sun Pharmaceutical Winlevi](/reviews/winlevi-clascoterone-cream-review) — CONDITIONAL 72/100 — Erythema on vehicle, 15.4%, exceeded erythema on drug, 12.2%.
- [R-35 Galderma Tri-Luma](/reviews/tri-luma-cream-review) — RECOMMENDED 85/100 — The comparator arm without hydroquinone cleared nobody at all in trial 1.
- [R-06 Musely The Anti-Aging Cream](/reviews/musely-the-anti-aging-cream-review) — RECOMMENDED 73/100 — A 91%-by-day-30 self-report, for a retinoid the same page says takes six to eight weeks.

## The practical version

Two things follow for anyone buying skincare, prescription or otherwise.

- Do the vehicle arm first. Daily sunscreen, sun avoidance, stopping the astringents and abrasives, identifying and avoiding your own triggers, and one bland moisturiser applied consistently. In these trials that combination produced success in between a quarter and four in ten people, depending on the condition. It is free, and every drug in this register was tested on top of it.
- When a percentage is quoted at you, ask what the other group got. If there was no other group, the number is a description of customers rather than a measurement of a drug — and it should be read that way regardless of how large it is.

We will keep publishing the vehicle arm alongside the drug arm in every review of a product that has one, and keep noting the absence in every review of a product that does not. It is the single most informative figure on a label and the one nearest to being free.

## Check the arithmetic before turning it into a ranking

The current TWYNEO manufacturer label has a Trial 1 table row whose displayed success percentages do not reconcile with the stated difference. The product review retains the original FDA document for comparison and leaves that row out of the chart. A reference should make a claim auditable, including when the source itself contains a discrepancy.

Even a consistent vehicle comparison does not settle a comparison with a different active treatment. CABTREO's and TWYNEO's separate programs are not a head-to-head trial. Preserve the comparator, population and endpoint before treating a larger percentage as a better prescription.

**READ THE TWO EVIDENCE RECORDS**

- [R-75 Mayne Pharma TWYNEO Cream](/reviews/twyneo-tretinoin-benzoyl-peroxide-review) — CONDITIONAL 80/100 — A documented table discrepancy, without an invented correction.
- [R-74 Bausch Health CABTREO Gel](/reviews/cabtreo-acne-gel-review) — CONDITIONAL 95/100 — Product-specific vehicle-controlled results.

## Sources

- [TWYNEO — current manufacturer prescribing information](https://www.twyneo.com/pdf/20250617_tywneo_pi.pdf) — February 2025 label names Mayne Pharma and a 30 g pump. Trial 1 success and difference figures in Table 4 conflict; that row is not charted here. Storage limits are product-specific. Checked 13 September 2026.
- [FDA — original TWYNEO approval label](https://www.accessdata.fda.gov/drugsatfda_docs/label/2021/214902s000lbl.pdf) — Historical 2021 label used only to investigate the Trial 1 table discrepancy. Its older pack size and opening limit are not used for current purchasing advice. Checked 13 September 2026.
- [DailyMed — CABTREO prescribing information](https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=9468da0f-9978-4c58-8135-0274c3415084) — Label revised March 2025: exact strengths, acne indication, two vehicle-controlled trials, contraindications and ten-week dispensing expiration. Checked 13 September 2026.

## Related records

- [L-04 The number nobody publishes](/ledger/the-number-nobody-publishes)
- [L-05 Compounded is not approved](/ledger/compounded-is-not-approved)
- [R-35 Galderma Tri-Luma](/reviews/tri-luma-cream-review) — RECOMMENDED
- [R-40 Galderma Soolantra](/reviews/soolantra-ivermectin-cream-review) — RECOMMENDED
- [PROFILE Bausch Health](/brands/bausch-health)
- [L-12 Rosacea prescriptions: persistent redness and bumps are different targets](/ledger/rosacea-prescriptions-redness-vs-bumps)

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## Elsewhere in the register

- [Review register](/reviews)
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- [The ledger](/ledger)
- [How we test](/how-we-test)
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