Questions About Optimal Dosing of Isotretinoin Persist, Expert Says

Doug Brunk

March 03, 2022

Although the Food and Drug Administration approved isotretinoin for severe recalcitrant acne 40 years ago, many questions about its optimal dosing remain to this day, according to Diane M. Thiboutot, MD.

These include, what is the ideal daily dose of isotretinoin? What is the ideal cumulative dose of isotretinoin to minimize relapse of acne? What is the ideal duration of isotretinoin therapy? How do you define relapse?

"Initially, it was recommended as 1–mg/kg per day dosing," Thiboutot, professor of dermatology at Penn State University, Hershey, said during the Orlando Dermatology Aesthetic and Clinical Conference. "As time went on and we became familiar with flares that some patients can have on that dose, it was recommended to start treatment at a dose of 0.5 mg/kg per day. Then there were trends for low dosing, intermittent dosing, and some of the more recent medical literature is talking about high dosing."

Clinical Studies

A multicenter study of 150 patients published in 1984 found that rates of relapse (retreatment needed) were 42% of patients of patients treated with 0.1 mg/kg daily, 20% in patients treated with 0.5 mg/kg daily, and 10% in patients treated with 1.0 mg/kg daily.

In a later study, researchers who followed 299 patients for 5 years post isotretinoin treatment found that there were more relapses in the 0.5-mg/kg group versus those treated with 1.0 mg/kg. Factors that contributed to the need for more treatment courses included lower-dose regimens (0.1 mg/kg and 0.5 mg/kg), having severe acne, being a female over the age of 25 at the onset of therapy, and having a prolonged history of acne.

More recently, investigators who conducted a single-center study of 1,453 patients treated with isotretinoin defined relapse as the need for a second course of isotretinoin. "They found that neither daily nor cumulative dosages influenced relapse of acne vulgaris in patients treated with varying doses of isotretinoin as long as treatment was continued for 2 or more months after the acne had completely resolved," said Thiboutot, a past president of the American Acne and Rosacea Society.

"The current evidence underpinning the 120-150 mg/kg cumulative threshold–dosing regimen is equivocal and is based on two low-grade studies," she noted. "Cumulative doses required for clearance appear lower for acne of mild to moderate severity and higher for more severe acne. Future investigations should use clinically relevant endpoints as end of treatment criteria and define treatment success in acne accurately."

Other studies have looked at whether higher doses of isotretinoin could reduce treatment failures in patients with acne, Thiboutot said. In a retrospective chart review of 102 patients with acne who had been treated with isotretinoin for at least 4 consecutive months and followed for over a year, 45.1% required further treatment and 15.7% received a second course of isotretinoin. Cumulative dose (mg/kg), follow-up period, duration of treatment, and daily dose during the last month of treatment were not significantly different between those who relapsed and those who did not relapse.

However, "while the cumulative dose of isotretinoin did not significantly impact acne relapse, patients who received a higher cumulative dose were less likely to require a second course of treatment," the authors wrote, adding that "female patients had a higher risk of needing retrial regardless of their cumulative dose." They commented that "prescribing a higher dose per weight may result in less severe acne recurrences and the need for further isotretinoin therapy."

Another study evaluated 116 patients who were treated to clearance with dosing at the discretion of the provider and defined relapse as subsequent treatment with an oral or topical agent. In the lower-dose treatment (less than 220 mg/kg; mean of 170 mg/kg) group, the relapse rate was 47.4%, compared with 26.9% in the higher-dose (greater than 220 mg/kg) group (P = .03). Cheilitis and xerosis during treatment was reported in nearly all patients in both treatment groups, but retinoid dermatitis was significantly more common among those in the higher-dose group (53.8% vs. 31.6%; P = .02). There were no significant differences in other adverse events between the two groups.

According to Thiboutot, variables to consider in selection of a daily dose include the presence of intense inflammation, cysts, nodules, potential difference in side-effect profiles with ethnicity, and an individual's degree of side effects and their level of comfort. "What are some of the concerns with higher doses? Those of us who have treated a lot of acne patients have had the unfortunate occurrence where you start someone on isotretinoin and their acne explodes, as do their cysts and nodules. Once that happens it's a bad situation and it takes you a while to get past it."

Acne Fulminans

Thiboutot was part of a panel of experts who assembled guidelines on the classification, management, and prevention of acne fulminans, published in 2017. "Acne fulminans can be induced by isotretinoin or it can occur on its own. If you have someone who has a lot of inflammation, a lot of cysts and nodules, it's probably best to start them on a lower dose with or without prednisone," she said.

Age at treatment is another variable that can affect the duration of response to isotretinoin. "If the patient is very young when they need isotretinoin, it's highly likely that they will need it again," Thiboutot said. "Also, adult females often need a repeat dose of isotretinoin. The cumulative dose is important, and the presence of truncal acne is a factor affecting duration of response. Truncal acne takes longer to clear, and it oftentimes needs a longer treatment course."

Data from the iPledge database indicate that 37% of 10- to 11-year-olds needed a repeat course of isotretinoin, "and as you get older, the need for retreatment is less," she said.

This article originally appeared on, part of the Medscape Professional Network.


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