# R-38 — Bausch Health Retin-A Micro — Tretinoin gel microsphere 0.04% / 0.06% / 0.08% / 0.1%

Four published strengths, a porous polymer reservoir that meters the drug out over hours, and a titration ladder printed on the carton. Two of the four rungs have no efficacy trial and no pharmacokinetic study of their own, and the label says so.

- **Canonical:** https://www.30plusskin.care/reviews/retin-a-micro-gel-review
- **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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## Verdict

- **Stance:** CONDITIONAL — Worth buying for a specific person with a specific problem. Read who.
- **Weighted score:** 76/100 across 75% of the scoring model
- **Score scope:** See assessed criteria
- **Category:** PRESCRIPTION MANUFACTURED / ACNE — RETINOID LADDER
- **Price:** $172 — PER 50 G PUMP · NO SUBSCRIPTION
- **Container size:** 20 G · 45 G TUBE · 50 G PUMP
- **Prescription:** yes
- **Compounded:** no
- **Assessment basis:** DESK REVIEW
- **Last updated:** 2026-08-02
- **Manufacturer page:** https://www.retinamicro.com/

This is the product that made a real titration ladder possible in a manufactured retinoid. Four strengths — 0.04%, 0.06%, 0.08% and 0.1% — each stated in milligrams of tretinoin per gram, in tubes and pumps of published fill weight. Compare that with the compounded services in this register, where the number is behind a consultation and the ladder is whatever the prescriber decides that month.

The delivery system is genuinely different. The tretinoin sits inside a methyl methacrylate/glycol dimethacrylate crosspolymer — a porous microsphere marketed as the Microsponge system — which holds the drug at the surface and releases it gradually rather than dumping it onto the stratum corneum at once. Systemic bioavailability was measured at 0.82% after a single application and 1.41% with repeated daily use, with plasma tretinoin essentially unchanged from baseline. That is a real measurement of a thing most products only assert.

The honesty is in what is missing. The label publishes efficacy trials for 0.1% and for 0.04%, and states plainly that clinical pharmacokinetic studies have not been performed with 0.08%, 0.06% or 0.04%. The two middle rungs of the ladder have neither efficacy data nor pharmacokinetic data of their own; they are interpolations between two studied endpoints. That is a defensible regulatory position and it is disclosed — but a four-strength ladder with data at two strengths is not the same thing as a four-strength ladder.

One more disclosure deserves airing because nothing else in this register has an equivalent. The label states that the components of the microspheres have shown potential for genetic toxicity and fetal malformation, and gives the detail: EGDMA was positive for structural chromosomal aberrations in vitro in mammalian cells without metabolic activation, and negative in the Ames assay and the in vivo mouse micronucleus test. Two of three assays negative, the positive one in vitro. That is a modest signal, correctly contextualised, and printed anyway.

## Actives, as published

| Active | Concentration | Role | Benchmark | Assessment | Flagged |
| --- | --- | --- | --- | --- | --- |
| Tretinoin | 0.04% / 0.06% / 0.08% / 0.1% | Retinoic acid receptor agonist, held in a porous polymer reservoir for gradual release | 0.025% to 0.1% across the acne trial literature | The full useful range, published rung by rung, with fill weights for each. The top and bottom rungs have trials behind them; the two in the middle do not. That is still four documented options against a compounded catalogue where we found tretinoin at seven different strengths, four of them below the bottom of the trial range and none of them on the page you buy from. | no |

## Scoring

| Criterion | Weight | Score | Note |
| --- | --- | --- | --- |
| EVIDENCE FOR THE ACTIVE | 30% | 68/100 | Four vehicle-controlled trials across two of the four strengths, with published lesion counts and global evaluations. Marked down hard because half the ladder has no efficacy data of its own, because the trials are small by modern standards — 67 to 111 subjects per arm — and because in one of them inflammatory lesions fell 29% against 24% on vehicle, a difference the label publishes and does not oversell. |
| FORMULATION INTEGRITY | 20% | 86/100 | The most interesting vehicle in the register. A porous crosspolymer reservoir that meters tretinoin out over hours, with measured systemic bioavailability of 0.82% and 1.41% and plasma levels shown to be essentially unaltered from baseline. Full excipient list, four strengths, published fill weights, an upright-storage pump. Marked down for the in vitro genotoxicity signal on a microsphere component, which the label discloses and contextualises. |
| DISCLOSURE | 15% | 90/100 | Publishes what it does not know: no pharmacokinetics for three of four strengths, no dermal carcinogenicity testing for any of them, an in vitro chromosomal aberration result on an excipient, animal photocarcinogenicity enhancement, and a trial result barely separated from vehicle. Concentrations, fill weights and excipients all published. Held back only because the two middle strengths are marketed with no data of their own and the label does not flag that as a limitation in plain language. |
| TOLERANCE IN USE | 15% | not scorable | Not assessed. The gradual-release rationale is a tolerability argument and the label reports skin irritation, burning, erythema, peeling, dryness, itching and dermatitis as the most common reactions without giving rates against vehicle. A panel comparing microsphere gel with a conventional gel at matched strength is the study nobody has published. |
| TEXTURE & WEAR | 10% | not scorable | Not assessed. A gel carrying opaque polymer microspheres behaves unlike either a cream or a clear gel and warrants a panel. |
| COST PER APPLICATION | 10% | 58/100 | Around $172 for a 50 g pump, with generic tretinoin microsphere gel available lower and conventional generic tretinoin lower still. Every pack size is published — 20 g and 45 g tubes, 50 g pumps — so cost per gram is computable at every strength, which is more than any compounded competitor in this register offers. |

_A criterion that cannot be assessed from published information is not guessed at. Its weight is removed from the denominator, and the coverage figure above says how much of the model survived._

## Strengths

- Four strengths, each printed with the milligrams of tretinoin per gram.
- Every pack size published — 20 g, 45 g, 50 g — so cost per gram is computable.
- A genuine titration ladder available from one manufacturer in one vehicle.
- Systemic bioavailability actually measured: 0.82% single dose, 1.41% repeated.
- Plasma tretinoin shown to be essentially unaltered from baseline after 28 days.
- States outright that no pharmacokinetic study exists for three of the four strengths.
- States that dermal carcinogenicity testing has not been performed for any strength.
- Publishes the in vitro genotoxicity signal on the microsphere component, with the two negative assays alongside.
- Publishes a trial arm where the drug barely separated from vehicle on inflammatory lesions.
- Tells patients that more product will not work faster.

## Weaknesses

- 0.06% and 0.08% have no published efficacy trial and no pharmacokinetic study.
- The four registration trials are small: 67 to 111 subjects per arm.
- In study 2 at 0.1%, inflammatory lesions fell 29% against 24% on vehicle.
- No adverse reaction rates against vehicle are published, only a list of common reactions.
- Animal work shows tretinoin may enhance the tumorigenic potential of ultraviolet light, and dark pigmentation did not overcome the effect.
- One microsphere component was positive for structural chromosomal aberrations in vitro.
- Indicated for acne only — photoageing use is off-label.
- Pregnancy: retinoid class, with rat and rabbit malformation data on this specific formulation.

## Suits

- Someone who wants to start low and climb deliberately, with the strength written on the carton at every step.
- Someone who has found conventional tretinoin gels too aggressive and wants the gradual-release version.
- Someone who wants to know what fraction of a topical retinoid actually reaches the bloodstream, because this label is where that number is published.
- Someone comparing a compounded 'personalised' retinoid ladder against a manufactured one with published rungs.

## Avoid if

- You are pregnant, trying to conceive or breastfeeding.
- You want data specific to the strength you are being given, and that strength is 0.06% or 0.08%.
- You want a wrinkle indication — this label has none, and R-34 does.
- You cannot commit to daily sunscreen; the photocarcinogenicity signal in animals is a class issue and this label states it.
- You are paying cash and generic tretinoin at a suitable strength is available to you.

## The full assessment

### What it is

Tretinoin held inside porous polymer microspheres suspended in a gel, at four strengths, approved for acne vulgaris in patients twelve and older, applied once daily in the evening. Around $172 for a 50 g pump. It is the closest thing in this register to a manufactured titration ladder.

**RECORD**

| Field | Value |
| --- | --- |
| BRAND | BAUSCH HEALTH |
| PRODUCT | RETIN-A MICRO (TRETINOIN) GEL MICROSPHERE |
| STRENGTHS | 0.04% · 0.06% · 0.08% · 0.1% |
| STATED AS | 0.4 / 0.6 / 0.8 / 1.0 MG PER GRAM |
| DELIVERY | METHYL METHACRYLATE / GLYCOL DIMETHACRYLATE CROSSPOLYMER |
| PACK SIZES | 20 G TUBE · 45 G TUBE · 50 G PUMP |
| EFFICACY TRIALS | 0.1% AND 0.04% ONLY |
| PHARMACOKINETICS | 0.1% ONLY |
| PRICE | ~$172 / 50 G PUMP |

### The ladder, and the two rungs with nothing under them

Four strengths is the single best argument for this product. A person who cannot tolerate 0.1% has three documented steps down without changing vehicle, manufacturer or prescription format. Nothing compounded in this register offers that, because compounded strengths are set per patient and never published.

> **READ SECTION 12.3 BEFORE YOU ASSUME THE LADDER IS EVENLY BUILT** — 'Clinical pharmacokinetic studies have not been performed with RETIN-A MICRO, 0.08%, 0.06% and 0.04%.' And section 14 publishes efficacy trials for 0.1% and 0.04% only. So of four marketed strengths: one has both efficacy and pharmacokinetic data, one has efficacy data alone, and two have neither. The middle of the ladder is interpolation between two measured points. This is normal regulatory practice for a strength series and it is disclosed in plain terms — but a patient told they have been 'stepped down to 0.06%' should know that 0.06% has never been studied on its own.

### What the two studied strengths did

**FIG. 1 — MEAN PERCENT REDUCTION IN LESION COUNTS AT WEEK 12** — Four vehicle-controlled trials, 67 to 111 subjects per arm. Studies 1 and 2 tested 0.1%; studies 3 and 4 tested 0.04%. The variability between studies of the same strength is larger than the difference between the strengths — which is what small trials look like, and why the label reports all four rather than the best one.

| Item | Value (% REDUCTION) | Note |
| --- | --- | --- |
| 0.1% — NON-INFLAMMATORY, STUDY 1 | 49 | Against 22% on vehicle |
| 0.1% — NON-INFLAMMATORY, STUDY 2 | 32 | Against 3% on vehicle |
| 0.1% — INFLAMMATORY, STUDY 1 | 37 | Against 18% on vehicle |
| 0.1% — INFLAMMATORY, STUDY 2 | 29 | Against 24% on vehicle — a five-point gap, published as found |
| 0.04% — NON-INFLAMMATORY, STUDY 3 | 37 | Against a 2% increase on vehicle |
| 0.04% — INFLAMMATORY, STUDY 3 | 44 | Against 13% on vehicle |
| 0.04% — INFLAMMATORY, STUDY 4 | 41 | Against 30% on vehicle |

_Scale maximum: 50% REDUCTION._

The investigator's global evaluation gives the cleaner picture. An 'excellent' result was reached by 35% and 28% of subjects on 0.1% against 11% and 9% on vehicle, and by 14% and 19% on 0.04% against 5% and 9%. Read that as: the strong version produces an excellent outcome in roughly three subjects in ten, the mild version in fewer than two, and the vehicle in about one.

### The number nobody else publishes: how much gets in

Percutaneous absorption was assessed in 44 healthy volunteers using radiolabelled drug over up to 28 days. Bioavailability was 0.82% after a single application and 1.41% with repeated daily use. Plasma concentrations of tretinoin and its three main metabolites ranged from 1 to 3 ng/mL and were essentially unaltered from baseline.

That is the answer to a question this register has been circling since R-12: when a topical is applied to skin, how much of it becomes a systemic exposure? For tretinoin from this vehicle, the answer is about one per cent, and the resulting plasma levels are indistinguishable from the endogenous background. It is a reassuring number and it is a measured one — which is exactly what compounded topicals containing hormones, corticosteroids or high-strength hydroquinone are unable to offer.

### The disclosure other labels would have left out

- Dermal carcinogenicity testing has not been performed with any of the four strengths.
- In a 91-week mouse study at concentrations near the clinical formulations, cutaneous squamous cell carcinomas and papillomas appeared in some female mice, and liver tumours in male mice — at doses exceeding the dermal maximally tolerated dose and within the background rate for the strain.
- Studies in hairless and pigmented mice suggest tretinoin may enhance the tumorigenic potential of carcinogenic doses of ultraviolet light, and dark pigmentation did not overcome the effect.
- Tretinoin itself was negative in the Ames assay and the in vivo mouse micronucleus assay.
- The components of the microspheres have shown potential for genetic toxicity and fetal malformation: EGDMA was positive for structural chromosomal aberrations in vitro in mammalian cells without metabolic activation, and negative in the Ames and in vivo micronucleus assays.
- Rat and rabbit reproductive studies on this specific formulation produced vertebral and rib alterations, domed head and hydrocephaly at 5 to 19 times the maximum recommended human dose.

> **THIS IS WHAT PROPORTIONATE RISK REPORTING LOOKS LIKE** — None of the above should stop anyone using a topical retinoid. Mouse tumours at supra-tolerated doses, one positive in vitro assay against two negatives, and animal malformations at multiples of human exposure are the standard furniture of a full nonclinical package. The point is that the furniture is in the room where you can see it. A compounded tretinoin sold on a monthly subscription has no nonclinical package at all — not a clean one, not a messy one. There is nothing to read, which is not the same as nothing to know.

### If you are considering it

- Start at 0.04% unless there is a reason not to, and ask what the plan is for stepping up.
- If you are put on 0.06% or 0.08%, know that those strengths have no trial of their own.
- Once nightly. The label says explicitly that more will not work faster and may cause marked redness and peeling.
- Cleanse with something mild and dry the skin before applying — the dosing section requires it.
- Avoid the creases of the nose, the eyes and the mouth.
- Sunscreen daily, and take the ultraviolet interaction seriously — the animal data on photocarcinogenesis are on this label for a reason.
- Store the pump upright.
- If the gel format is the problem rather than the drug, R-36 is the same molecule in a lotion.

### Where we stand

At 76 this is a well-engineered old drug in an unusually well-documented package, held back by a ladder that is only half built and trials that were small even when they were run. It is the register's clearest demonstration that publishing a strength series is not the same as evidencing one.

Its real value here is as a control. Every compounded service in this register sells the idea of a personalised strength. This is what a strength series looks like when a regulator has seen it: four numbers on four cartons, efficacy data at two of them, pharmacokinetics at one, and a sentence telling you which is which.

**READ ALONGSIDE**

- [R-36 Bausch Health Altreno](/reviews/altreno-tretinoin-lotion-review) — RECOMMENDED 79/100 — The same drug in a lotion, with adverse reaction rates published against vehicle.
- [R-08 Musely The Eye Serum](/reviews/musely-the-eye-serum-review) — CAUTION 32/100 — Tretinoin at 0.001% — one hundredth of the top rung here, with no data at any rung.
- [L-04 The number nobody publishes](/ledger/the-number-nobody-publishes) — Why an absorbed fraction of 1.41% is worth more than a satisfaction survey.

## Where to buy

| Retailer | Price | Link | Note | Commission-bearing |
| --- | --- | --- | --- | --- |
| Prescriber + retail pharmacy | ~$172 / 50 g pump | https://www.retinamicro.com/ | Prescription only. Generic tretinoin microsphere gel exists at lower cost. Often covered for acne. | no |

We earn nothing on this link. If you are starting, ask for 0.04% and the reason for whichever strength you are given — the ladder only helps if someone is climbing it deliberately.

**Featured alternative:** [CoreAge Rx Smooth Move](https://www.coreagerx.com/product/smooth-move/?utm_source=30plusskin&utm_medium=affiliate&utm_campaign=review&utm_content=retin-a-micro-gel-review&utm_term=markdown) — Tretinoin with niacinamide and vitamin C for fine lines and texture. From $42 / month advertised.

## Sources

- [FDA-approved labelling — RETIN-A MICRO (tretinoin) gel, Bausch Health US LLC](https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=08ab7e0c-1437-455f-815c-98904d96a289) — The four strengths stated as 0.4, 0.6, 0.8 and 1.0 mg of tretinoin per gram; the Microsponge crosspolymer and the full excipient list; the four vehicle-controlled trials with lesion reductions and investigator global evaluations for 0.1% and 0.04%; the statement that clinical pharmacokinetic studies have not been performed with 0.08%, 0.06% or 0.04%; bioavailability of 0.82% and 1.41% with plasma levels of 1 to 3 ng/mL; the absence of dermal carcinogenicity testing; the mouse tumour and photocarcinogenicity findings; the EGDMA in vitro chromosomal aberration result; the rat and rabbit reproductive findings; and the published pack sizes. Read 2 August 2026.
- [GoodRx — retinoid class pricing including Retin-A Micro](https://www.goodrx.com/classes/retinoids) — Cash pricing from around $172 for Retin-A Micro, against roughly $38 for generic tretinoin. Retrieved 2 August 2026.

## Related records

- [L-09 The vehicle is a dose](/ledger/the-vehicle-is-a-dose)
- [R-36 Bausch Health Altreno](/reviews/altreno-tretinoin-lotion-review) — RECOMMENDED
- [R-08 Musely The Eye Serum](/reviews/musely-the-eye-serum-review) — CAUTION
- [L-04 The number nobody publishes](/ledger/the-number-nobody-publishes)
- [L-14 Tretinoin online: a pharmacy prescription or a custom subscription?](/ledger/tretinoin-online-visit-vs-subscription)
- [R-65 Strut Health Tretinoin Cream](/reviews/strut-tretinoin-cream-review) — CAUTION

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---

## Elsewhere in the register

- [Review register](/reviews)
- [Active monographs](/actives)
- [Brand register](/brands)
- [Evidence register](/evidence)
- [The ledger](/ledger)
- [How we test](/how-we-test)
- [Agent guide](/llms.txt)
- [Sitemap](/sitemap.xml)

_SOURCE-BASED ASSESSMENTS. PUBLISHER PREFERENCES ARE IDENTIFIED SEPARATELY._