Adapalene vs Tretinoin: who reigns supreme?

Chronological ageing involves changes to underlying skin structures. Photoaging involves the premature ageing of skin due to cumulative sun exposure. Chronological and photoaging both appear similar at surface level and to the naked eye but they have histological differences. Amongst the retinoids, tretinoin possibly is the most potent and certainly the most widely investigated retinoid for the management of photoaging.

Although retinoids show promise in the treatment of skin aging, irritant reactions such as burning, scaling or dermatitis associated with retinoid therapy limit their acceptance by patients. This problem is more prominent with tretinoin and tazarotene whereas other retinoids mainly represented by retinaldehyde and retinol are considerably less irritating and of course, also less potent compared to tretinoin. This lead to newer drug discoveries for other types of retinoids.

This article will aim to explore:

• Why are there so many different topical retinoids?
• What is Adapalene?
• Is Adapalene right for me?

Why are there so many different topical retinoids?

Tretinoin is the most widely studied retinoid when it comes to photoaging. Tretinoin was the first retinoid to be studied for hyperpigmentation in individuals with melanin-rich skin. A 40-week double-blind study involved 68 Black men and women who had dark spots from acne, shaving issues, eczema, ingrown hairs, and folliculitis. Results showed improvements with tretinoin 0.1% cream starting at week four. However, like many older tretinoin products, 50% of those treated experienced skin reactions which can contribute to unwanted pigmentary changes. To address issues of irritation and tolerability, novel lotion formulations were developed for tretinoin. Tretinoin 0.05% lotion was developed as well as the discovery of milder forms of retinoids. They include retinyl esters, retinol and retinaldehyde, which are all converted to tretinoin. The milder forms of retinoids are less irritating but are also less potent compared to tretinoin. 

Their potency and side effects depend on their preferential binding to different retinoid receptor sub-types and stability before conversion to tretinoin.

What is Adapalene?

Adapalene is considered to be a third-generation synthetic retinoid. It targets abnormal skin cell turnover and skin cell differentiation. It also possesses anti-inflammatory properties. Due to its receptor selectivity, it causes less skin irritation compared to Tretinoin. Adapalene is successfully being used for the treatment of acne.

When it comes to skin brightening, patients treated with adapalene gel showed a notable lightening of photoaged lesions compared to those using a vehicle gel after just one month. After nine months, 57% of patients using adapalene 0.1% and 59% using 0.3% had lighter lesions, while only 36% in the vehicle group saw similar results (p < 0.05). Additionally, histological assessments showed fewer abnormal skin cells and lower melanin levels in the skin of those treated with adapalene versus the vehicle group. A review of before and after photographs after nine months treatment showed marked improvements in wrinkles and other signs of photoaging with adapalene compared to the vehicle. Adapalene was well tolerated by all patients in the study. However, further large-scale clinical trials are needed to confirm its effectiveness in head to head studies against tretinoin.

Adapalene 0.1% is now available in Australia over the counter without a prescription.

Is adapalene right for me?

Evidence from clinical trials indicate that topical retinoids should be considered a first-line therapy in patients with acne and hyperpigmentation, unless contraindicated (e.g. pregnancy). Due to its selective receptor subtypes, Adapalene has proven to be successful for managing acne and hyperpigmentation/discolouration associated with acne. For patients with sensitive skin, new vehicle formulations may be less irritating than older formulations.

Adapalene is currently also prescribed off label for photoageing due to better patient acceptability at higher dosages.

Can I use Adapalene for anti-ageing?

A small study done on 40 women looked at using 0.3% adapalene, once daily for 24 weeks. In this study, adapalene was able to decrease forehead wrinkles, periorbital wrinkles, and improved overall hydration.

In addition, other studies comparing Adapalene vs tretinoin have only included Adapalene 0.3%. So far, it is safe to say Adapalene less than 0.3% is inferior to tretinoin when it comes to boosting collagen and reducing wrinkles.

If acne and acne marks is your primary concern but you also want the secondary benefits of anti-ageing, then adapalene maybe appropriate for you.

 REFERENCES

1. Mukherjee, S et al. Retinoids in the treatment of skin aging: an overview of clinical efficacy and safety. J Clin Interv Aging. 2006 Dec; 1(4): 327–348.
2. Callender, V.D., Baldwin, H., Cook-Bolden, F.E. et al. Effects of Topical Retinoids on Acne and Post-inflammatory Hyperpigmentation in Patients with Skin of Color: A Clinical Review and Implications for Practice. Am J Clin Dermatol 23, 69–81 (2022). https://doi.org/10.1007/s40257-021-00643-2
3. Bagatin, E et al. Comparable efficacy of adapalene 0.3% gel and tretinoin 0.05% cream as treatment for cutaneous photoaging. European Journal of Dermatology, 28, 343-350.