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Skin, hair & anti-aging

Isotretinoin

The strongest treatment for severe acne - highly effective, but with a strict safety profile.

1 min read 9 sources

To the product To the sources
Large blue 3D molecule on a white podium in a bright lab, symbolic image for isotretinoin
Compound approved · since 1982 according to ChEMBL

Summary

At a glance

Sources checked on 26 Oct 2026

Sebum excretion
-90 %

after 4 months at the classic level, comedone formation -70 percent3

Nearly clear
90 %

share with 95 percent fewer inflamed lesions, highest of three levels, lowest 58 percent1

Risk of major malformations
25.6 -fold

relative risk with use during pregnancy, 154 pregnancies5

Uptake without a meal
39.6 %

level when fasting compared with a fatty meal, original form7

Triglycerides newly raised
44 %

with normal baseline values, 13,772 treated people4

  • Isotretinoin is a retinoid that acts at the retinoic acid receptors according to ChEMBL. It shrinks the sebaceous glands and strongly lowers sebum production.93
  • In a trial with three levels 58 to 90 percent of people with severe acne reached a 95 percent drop in inflamed lesions. The higher level worked better.1
  • Side effects are common, above all dry skin and lips. Many see blood lipids and less often liver enzymes rise, mostly temporarily.24
  • In pregnancy isotretinoin is strongly harmful to the unborn child: the risk of major malformations was 25.6 times higher.5
  • Isotretinoin is an approved compound. Everything here is the state of research, not a recommendation.9
Profile

Updated June 2026

How long does it stay in the body?

Share left after one dose, calculated with a half-life of ~15 hours

Half-life ~15 hours
After 30 hours: 25 %
Hour 15 · 50 %Hour 24, next dose · 33 %Hour 30 · 25 %Hour 45 · 12.5 %Hour 75 · 3.1 %

Simplified model without an absorption phase, half-life from the TPD lexicon. The lexicon gives 10 to 20 hours, we calculate with the middle.

Class
Retinoid

vitamin A derivative, oral

Use
Oral

1x per day with fat

Half-life
about 10-20 hours
Status
Prescription

teratogenic

Sizes
10 to 40 mg

5 sizes in the shop

Contents 12 sections
  1. At a glance
  2. What is Isotretinoin?
  3. Research status
  4. How it works
  5. Use and dosing
  6. Important warning
  7. Side effects
  8. Storage
  9. Related compounds
  10. FAQ
  11. Glossary
  12. Sources

What is Isotretinoin?

Isotretinoin (13-cis-retinoic acid) is an oral vitamin A derivative and the most effective treatment for severe, treatment-resistant acne. It can clear acne durably but has a strict safety profile - above all it is strongly harmful to a fetus.

This information is for research and educational purposes only. No medical advice.

Comparison

Retinoids: tablet or cream

Isotretinoin is swallowed, tretinoin is applied to the skin. According to ChEMBL both act at the retinoic acid receptors. Tap a card to open its entry.

Retinoid as a tablet Isotretinoin RAR
Retinoid as a cream Tretinoin (Retin-A) RAR

Simplified: same receptor family, different use. As a tablet isotretinoin acts throughout the body, hence the effect on blood lipids and the strict warning in pregnancy. 9

Study results

What the trials measured

Interactive: switch tabs, tap points, show or hide arms. Arms are named relative to each other, no dosing advice.

Nearly clear after 20 weeks1

Share with 95 percent fewer inflamed lesions, 150 participants, three levels per kg body weight

95 percent fewer inflamed lesions1
Lowest level (per kg body weight) 58%
Middle level 80%
Highest level (classic) 90%

Single trial from the Cochrane review, low-quality evidence. In a second trial with even lower levels inflamed lesions fell by 79 to 84 percent.

Sebum and comedones after 4 months3

Reduction in percent, classic level

Sebum excretion3
Isotretinoin -90%
Comedone formation3 measured by follicular casts
Isotretinoin -70%

Values from the abstract. If sebum excretion returned close to baseline afterwards, that was a poor sign for long-term success.

Glass block with a multi-layer skin model, hair follicle and sebaceous gland, on a glass pedestal in a lab
Studies on severe acne, sebum and lab values. Symbolic image.

Research status

Where the research stands

Isotretinoin has been approved since 1982. On ClinicalTrials.gov 214 trials list isotretinoin, many of them in childhood cancer. Shown are registered phase 3 trials on acne and rosacea. As of 26 Oct 2026. 8

  1. Preclinical Animal studies showed the harm of retinoids to the unborn early on
  2. Phase 1 no registered trial
  3. Phase 2 no registered trial
  4. Phase 3 4 trials, 4 completed
  5. Approval since 1982 according to ChEMBL
1,141 participants in phase 3 Approved: ChEMBL lists isotretinoin with phase 4 as the highest phase and first approval in 1982.9
Show all 4 phase 3 trials on a timelineHide timeline 4 completed 0 running 0 with results
Phase 3

Bar: start to primary endpoint (planned for running trials). Green = completed, blue = progress until 26 Oct 2026.

How it works

Isotretinoin drastically shrinks the sebaceous glands and lowers sebum production, normalizes follicle keratinization and acts anti-inflammatory. It thus targets all the key acne mechanisms at once.

Where it acts

Where isotretinoin acted in studies

Tap a point or a card. Colour = retinoic acid receptors, grey = observed in studies.

  1. Skin and sebaceous glands

    Sebum excretion -90 percent, comedone formation -70 percent3

    RAR
  2. Blood lipids

    Triglycerides newly raised in 44, cholesterol in 31 percent4

    Observed in trials
  3. Liver

    Transaminases newly raised in 11 percent, mostly mildly4

    Observed in trials
  4. Mood

    Meta-analysis: no increased depression risk, scores fell on average6

    Observed in trials

Targets in the ChEMBL database9

Compound CHEMBL547: one recorded mechanism, agonist with direct binding to the human receptor.

Retinoic acid receptors (alpha, beta, gamma)
Gene
RARA, RARB, RARG
UniProt
P10276, P10826, P13631
ChEMBL
CHEMBL2363069
Action
Agonist, direct binding
Transparent skin layer with glassy sebaceous glands and a follicle, blue molecules on top
Isotretinoin shrinks the sebaceous glands and lowers sebum production. Symbolic image.

Use and dosing

Dosing

Dosing, titration and syringe

Loading the dosing information …

  • Getting started and stepping up, drawn as a staircase
  • Units on the U-100 syringe for every step
  • How long one vial lasts
White folding box with the TPD logo, next to it a blister with ten white tablets and two loose tablets on a bright lab bench
In a blister. With a fatty meal, which improves uptake. Symbolic image.

Important warning

Isotretinoin is strongly teratogenic - absolutely contraindicated in pregnancy as it causes severe birth defects. Reliable contraception before, during and after use is mandatory. This substance belongs strictly under medical supervision.

Side effects

  • Very common: dry skin, lips and eyes, sensitive skin.
  • Muscle and joint aches, headaches.
  • Rise in liver values and blood lipids - monitoring needed.
  • Rarely low mood; teratogenic (see warning).

Tolerability

Lab values on isotretinoin

Out of 100 treated people with normal baseline values, in how many the value became abnormal.

44 of 100 Isotretinoin
Event Isotretinoin
Triglycerides4 44%
Total cholesterol4 31%
Liver enzymes (transaminases)4 11%

Moderate to severe abnormalities were mostly temporary. Blood count values rarely changed. In trials against comparison treatments there were twice as many side effects, more than half concerned dry skin.42

Storage

Store dry and cool, protected from light. Out of reach of children.

Three white capsule bottles on a bright shelf next to a folded light blue towel
Store dry, cool and protected from light. Symbolic image.
Level · Isotretinoin

How the level builds up

One dose per day: each dose adds to what is left of the previous one.

Lexicon: Oral, 1x per day with fat
Peak 1.49×Trough 0.49×
Day 2 · 3. dose
1.44× of the first dose
Plateau
from Day 2

96 % of the plateau after dose 3

Peak
1.49×

of the first dose

Trough
0.49×

before the next dose

Simplified model, values relative to the first dose, no dosing information. Dashed: the first dose alone, green: the plateau.

Related

Related compounds

Same receptors: all in the TPD lexicon.

Isotretinoin
Tretinoin (Retin-A) Retinoid applied to the skin

FAQ

Common questions about Isotretinoin

Short answers, each backed by the sources below.

Is isotretinoin approved?

Yes. ChEMBL lists isotretinoin with phase 4 as the highest phase and first approval in 1982. ClinicalTrials.gov lists 214 trials with isotretinoin, as of 26 October 2026.98

How does isotretinoin work?

According to ChEMBL it acts at the retinoic acid receptors. At the classic level sebum excretion fell by 90 percent after 4 months and comedone formation by 70 percent. Colonisation of the skin with acne bacteria also fell.93

How well does it work in acne?

A systematic review of 11 trials with 760 participants found that isotretinoin always reduced lesion counts more than the comparison treatment. In a trial with three levels 58, 80 and 90 percent reached a 95 percent reduction. The Cochrane review rates the evidence as mostly low.21

Why with a fatty meal?

Because uptake depends strongly on fat. When fasting the original form reached only 39.6 percent of the level measured after a fatty meal.7

How dangerous is isotretinoin in pregnancy?

Very. In an investigation of 154 pregnancies with isotretinoin the risk of major malformations was 25.6 times higher. Mainly ears, face, heart, thymus and nervous system were affected. Among the 36 pregnancies followed from the start, 5 infants had malformations.5

Does isotretinoin cause depression?

A meta-analysis of 31 studies found no increased risk. Depression scores fell on average during treatment, probably because the acne improved. There were no randomised trials on this. Single trial withdrawals due to low mood are described.62

Which side effects are common?

Most often dry skin and lips. In trials there were twice as many side effects as with comparison treatments. With normal baseline values triglycerides rose in 44 percent, cholesterol in 31 percent and liver enzymes in 11 percent, mostly temporarily.24

Glossary

Terms explained briefly

Dotted words in the text open these explanations directly.

13-cis-retinoic acid
Chemical name of isotretinoin, a form of retinoic acid.
Comedo
Blackhead or whitehead: a clogged hair follicle, open or closed.
Cumulative total dose
The sum of all single doses over the whole treatment, usually counted per kg body weight.
Keratinisation
Formation of horny cells. If it is disturbed in the follicle, the follicle clogs and comedones form.
Retinoid
Derivative of vitamin A. Retinoids control the growth and maturation of skin cells via their own receptors.
Sebaceous gland
Gland at the hair follicle that produces the skin's oil (sebum). Too much sebum favours acne.
Teratogenic
Can harm an unborn child in the womb and cause malformations.
Transaminases
Liver enzymes in the blood. If they rise, liver cells are irritated.
Triglycerides
The most common fats in the blood. On isotretinoin they rise in many people.

Evidence

Sources

Show all 9 sourcesHide sources 7 Studies1 Trial registry1 Database checked 26 Oct 2026

Studies

  1. Cochrane review: isotretinoin for acne

    Costa et al., Cochrane Database of Systematic Reviews, 2018

    DOI 10.1002/14651858.CD009435.pub2 PMID 30484286
    Checked 26 Oct 2026 via doi.org, Crossref, PubMed
  2. Systematic review of efficacy and adverse events

    Vallerand et al., British Journal of Dermatology, 2018

    DOI 10.1111/bjd.15668 PMID 28542914
    Checked 26 Oct 2026 via doi.org, Crossref, PubMed
  3. Sebum, comedones and long-term benefit

    Cunliffe et al., Dermatologica, 1987

    DOI 10.1159/000248869 PMID 2446935
    Checked 26 Oct 2026 via doi.org, Crossref, PubMed
  4. Lab values in 13,772 treated people

    Zane et al., Archives of Dermatology, 2006

    DOI 10.1001/archderm.142.8.1016 PMID 16924051
    Checked 26 Oct 2026 via doi.org, Crossref, PubMed
  5. Malformations after isotretinoin in pregnancy

    Lammer et al., New England Journal of Medicine, 1985

    DOI 10.1056/NEJM198510033131401 PMID 3162101
    Checked 26 Oct 2026 via doi.org, Crossref, PubMed
  6. Meta-analysis of isotretinoin and depression

    Huang und Cheng, Journal of the American Academy of Dermatology, 2017

    DOI 10.1016/j.jaad.2016.12.028 PMID 28291553
    Checked 26 Oct 2026 via doi.org, Crossref, PubMed
  7. Uptake with and without a fatty meal

    Webster et al., Journal of the American Academy of Dermatology, 2013

    DOI 10.1016/j.jaad.2013.05.036 PMID 23953888
    Checked 26 Oct 2026 via doi.org, Crossref, PubMed

Trial registry

  1. All trials with isotretinoin on ClinicalTrials.gov

    ClinicalTrials.gov, U.S. National Library of Medicine

    Checked 26 Oct 2026 via ClinicalTrials.gov API v2

Database

  1. Isotretinoin and tretinoin in ChEMBL (targets and approval)

    ChEMBL, EMBL-EBI (CHEMBL547, CHEMBL38)

    Checked 26 Oct 2026 via ChEMBL

In the shop

Isotretinoin in the catalog

Sizes, prices and shipping times are on the product page.

To the product