Comparison of the Pharmacokinetics and Phototoxicity of Protoporphyrin IX Metabolized from 5-Aminolevulinic Acid and Two Derivatives in Human Skin In Vivo¶

Photodetection and Safety of 5-Aminolevulinic Acid-Induced Porphyrin in Patients With Cervical Intraepithelial Neoplasia

BACKGROUND AND OBJECTIVES

5-Aminolevulinic acid (5-ALA) is a porphyrin-based photosensitizer and has been used for photodynamic therapy of cervical intraepithelial neoplasia (CIN). In this study, photodetection and safety of 5-ALA-induced porphyrin in CIN tissues were assessed.

STUDY DESIGN/MATERIALS AND METHODS

A total of 42 patients for whom colposcopy or loop electrosurgical excision procedure (LEEP) was planned were administered 10%, 20%, or 30% 5-ALA locally on the surface of the cervix for 1.5-18 hours. At different times after application, the fluorescence intensity of 5-ALA-induced porphyrin on CIN and non-CIN lesions of the cervix was detected.

RESULTS

Fluorescence intensity was correlated with drug concentration and application time. With 20% 5-ALA, the porphyrin fluorescence intensity increased over time, reaching a peak after 6 hours of application intervals in CIN. There was no significant difference in fluorescence intensity between CIN lesions and chronic cervicitis (benign tissue) or among CIN lesions of different severities. Three adverse events were considered related to the drug; however, these had no significant correlation with the drug concentration or application time.

CONCLUSIONS

5-ALA at 10%-30% concentration is safe in patients with CIN. For further treatment, we recommend the application of 20% 5-ALA, 6 hours before photodynamic therapy in CIN.

CLINICAL TRIAL REGISTRATION

This study was registered at http://www.chinadrugtrials.org.cn (registration number: CTR20130326) in accordance with the requirements of the National Medical Products Administration in China. Considering that there is no English version of the above website, we made a retrospective registration on http://www.chictr.org.cn (registration number ChiCTR1800016755) in 2018. Lasers Surg. Med. © 2020 Wiley Periodicals LLC.

Phototoxic reaction and porphyrin fluorescence in skin after topical application of methyl aminolaevulinate

BACKGROUND

Photodynamic therapy using topical methyl aminolaevulinate (MAL) is a new treatment modality for skin disorders. MAL is metabolized into endogenous porphyrins, which act as photosensitizers when illuminated.

OBJECTIVES

To evaluate the severity and duration of skin photosensitivity after MAL application, and to investigate its relation to the presence of endogenous porphyrins.

METHODS

Placebo and 160 mg g(-1) MAL creams were randomly assigned to contralateral sites located at the forearms and fingertips of 16 healthy volunteers and were applied for 3 h. The porphyrin content in the skin was monitored by in situ fluorescence measurements following cream removal. Phototoxic reaction was evaluated after exposure to a high dose of red light.

RESULTS

The porphyrin fluorescence in forearm skin peaked about 1 h after the cream removal, was halved after 8 h, and was reduced by > 90% within 24 h. Most forearm sites were photosensitive at 1 and 8 h following cream removal. Six subjects were still sensitive at 24 h, and at this time point the phototoxicity was coincidental with residual porphyrin fluorescence. In general, all reactions were mild or moderate, and included pain, erythema, oedema and transient hyperpigmentation. No photosensitivity or porphyrin fluorescence was detected at 48 h. At the fingertips photosensitivity was absent except for sporadic cases of mild pain.

CONCLUSIONS

Topical MAL application and exposure to red light induced mild and moderate phototoxicity. The photosensitivity ceased within 24-48 h after cream removal, and its duration was associated with the degradation of porphyrins.