AZELAIC ACID
Clinical safety rating: safe
Animal studies have demonstrated safety
Azelaic acid is a dicarboxylic acid with antimicrobial activity against Propionibacterium acnes and Staphylococcus epidermidis. It normalizes keratinization and reduces inflammation by inhibiting reactive oxygen species generation and neutrophil chemotaxis.
| Metabolism | Minimal systemic absorption after topical application. Absorbed portion is metabolized via beta-oxidation to shorter-chain dicarboxylic acids; not significantly metabolized by cytochrome P450. |
| Excretion | Approximately 65% of absorbed azelaic acid is excreted unchanged in urine, with <1% as metabolites (C9 dicarboxylic acid derivatives). Fecal excretion accounts for <1%. |
| Half-life | Terminal elimination half-life is approximately 12 hours (range 8-15 hours) for oral administration; for topical application, systemic half-life is similar after absorption but minimal systemic exposure occurs. |
| Protein binding | Approximately 30-40% bound to plasma proteins, primarily albumin. |
| Volume of Distribution | Apparent volume of distribution is approximately 0.6 L/kg after oral administration, indicating distribution into total body water. |
| Bioavailability | Topical: Systemic bioavailability is very low (<4% of applied dose absorbed). Oral: Rapid and nearly complete absorption (≥90% bioavailability) but oral formulation is not clinically used; only topical formulations are available. |
| Onset of Action | Topical: Clinical improvement in acne vulgaris and rosacea may be observed within 2-4 weeks of twice-daily application, with maximal effect by 12-24 weeks. |
| Duration of Action | Topical: Duration of action is sustained with continuous use; lesion counts decrease over weeks. After discontinuation, benefit may persist for weeks due to normalization of follicular keratinization and reduction in Propionibacterium acnes. |
Topical: Apply a pea-sized amount (approximately 0.5 g) of 15% or 20% gel/cream to affected areas twice daily (morning and evening). Oral: 500 mg to 1000 mg twice daily for rosacea (not FDA approved; used off-label).
| Dosage form | AEROSOL, FOAM |
| Renal impairment | No specific guidelines; systemic absorption is minimal (<5%) with topical use. For oral use (rare), caution with severe renal impairment (CrCl <30 mL/min); consider dose reduction based on tolerability. |
| Liver impairment | No adjustment required for topical use. For oral use, no specific guidelines; use with caution in severe hepatic impairment (Child-Pugh C) due to limited data. |
| Pediatric use | Topical: Safety and efficacy not established in children <12 years; for off-label use, apply same as adult (pea-sized amount twice daily). Oral: Not recommended in pediatric patients. |
| Geriatric use | No specific dose adjustment needed; use same as adult dosing. Monitor for local skin reactions (erythema, peeling) due to potential age-related skin thinning. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
No significant drug interactions Avoid contact with eyes and mucous membranes May cause hypopigmentation in patients with dark complexions.
| Breastfeeding | Systemic absorption after topical application is minimal (approximately 4%). It is unknown whether azelaic acid is excreted in human milk. The milk-to-plasma (M/P) ratio has not been determined. Due to low systemic absorption, the risk to a nursing infant is likely low. However, caution is advised; consider applying to minimal surface areas and avoiding application to the breast area. |
| Teratogenic Risk | Azelaic acid is a topical dicarboxylic acid with negligible systemic absorption (approximately 4%). No adequate and well-controlled studies in pregnant women exist. Animal studies with oral doses up to 2500 mg/kg/day in rats and 500 mg/kg/day in rabbits did not show teratogenicity, but systemic exposure was much lower than topical use. Based on limited human data and minimal systemic exposure, the risk of major birth defects is considered low. The FDA has not assigned a pregnancy category (previously category B). No specific fetal risks by trimester have been documented. |
■ FDA Black Box Warning
None
| Common Effects | acne vulgaris |
| Serious Effects |
["Hypersensitivity to azelaic acid or any component of the formulation"]
| Precautions | ["Hypopigmentation may occur; use with caution in patients with dark skin","Local irritation (erythema, scaling, stinging) common; reduce frequency if irritation occurs","Avoid contact with eyes, mouth, and mucous membranes","Exacerbation of acne or rosacea may occur occasionally"] |
| Food/Dietary | No known food interactions with topical azelaic acid. Oral azelaic acid (not marketed) may have theoretical interaction with high-fat meals affecting absorption, but topical use is not affected. No dietary restrictions required. |
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| Fetal Monitoring | No specific maternal or fetal monitoring is required during pregnancy or lactation. Routine prenatal care is sufficient. Monitor for local skin irritation at application site. |
| Fertility Effects | Azelaic acid has no known adverse effects on human fertility. In animal studies, oral doses up to 2500 mg/kg/day in rats showed no impairment of fertility. Topical use with minimal systemic absorption is unlikely to affect reproduction. |
| Clinical Pearls | Azelaic acid is a dicarboxylic acid with antibacterial, anti-inflammatory, and antikeratinizing properties. It is effective for mild to moderate acne vulgaris and rosacea. It can cause hypopigmentation, which is reversible upon discontinuation, particularly in dark-skinned patients. Use gel formulation for acne and cream for rosacea. It may take 4 weeks for initial improvement and up to 12 weeks for maximal effect. Avoid concurrent use with other keratolytic agents to prevent excessive irritation. |
| Patient Advice | Apply a thin layer to clean, dry skin twice daily (morning and evening). · Avoid contact with eyes, mouth, and mucous membranes. · Mild stinging or burning may occur initially, but it usually subsides with continued use. · Do not use occlusive dressings over the application site. · Use sunscreen daily as azelaic acid may increase sensitivity to sunlight. · If irritation persists or becomes severe, reduce frequency or discontinue and consult healthcare provider. · Improvement may be seen within 4 weeks, but full benefit may take up to 12 weeks. · Do not wash treated area immediately after application. |