# A-13 — Doxycycline 40 mg

An oral tetracycline deliberately dosed under the antibacterial threshold, with a label that forbids using it for infection. The answer to every undosed antibiotic in this register.

- **Canonical:** https://www.30plusskin.care/actives/doxycycline-40
- **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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## Datasheet

- **INN / INCI:** Doxycycline
- **Also known as:** Anti-inflammatory dose doxycycline
- **Family:** Tetracycline — sub-antimicrobial exposure
- **Molecular weight:** 444.43 g/mol
- **Layer reached:** DERMIS
- **Prescription only:** yes
- **Evidence grade:** A
- **Controlled trials on file:** 1
- **Strength range recorded:** 40%–40%
- **Representative reference concentration:** 40%
- **Irritation (0–10):** 2
- **Onset:** 16 WK
- **Stability:** STABLE

## Mechanism

The concentration marker is not a recommended dose or a claim that other strengths are untested. Compare the vehicle, indication and trial population.

At 40 mg split into 30 mg immediate and 10 mg delayed release, plasma concentrations stay below those required to treat bacterial disease while retaining inhibition of matrix metalloproteinases and neutrophil chemotaxis.

## Measured endpoints

| Endpoint | Effect vs comparator | Window | Record |
| --- | --- | --- | --- |
| IGA clear or almost clear | +11.3% | 16 WK | REF-09 — Oracea — study 1, inflammatory lesions of rosacea (Randomised, placebo-controlled, multi-centre Phase 3, n=251, grade A) |
| Long-term effect on bacterial flora | 0% | 78 WK | REF-10 — Oracea — 18-month bacterial flora study (In vivo microbiological study at comparable drug exposure, oral cavity, skin, intestinal tract and vagina, n=0, grade B) |

## Layering

- **Do not layer with:** Pregnancy and breastfeeding, Any use as an antibiotic, Doses above 40 mg
- **Pairs with:** Topical ivermectin, Topical azelaic acid, Daily sunscreen

## Notes

- The limitations of use forbid treating bacterial infections, providing antibacterial prophylaxis or reducing organisms associated with any bacterial disease.
- In vivo studies at comparable exposure for up to eighteen months found no detectable long-term effect on the bacterial flora of the oral cavity, skin, intestinal tract and vagina.
- The patient counselling section warns that exceeding 40 mg increases the likelihood of bacteria developing resistance. More is not a stronger version of this drug.
- It does nothing for erythema, and the label says so three separate times.
- Sixteen weeks is the longest controlled duration in this register.

## Products in the register containing it

| No. | Product | Stance | Score | Document |
| --- | --- | --- | --- | --- |
| R-48 | Galderma Oracea | RECOMMENDED | 80/100 | /reviews/oracea-doxycycline-40mg-review |
| R-24 | Dermatica Rosacea Treatment | CONDITIONAL | 71/100 | /reviews/dermatica-rosacea-review |

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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._