title: Evaluation of the penetration of 5-aminolevulinic acid through basal cell carcinoma: a pilot study.
abstract: Aminolevulinic acid (ALA) is a charged, hydrophilic molecule that penetrates poorly through cellular structures. This property has been implicated in the poor clinical response of non-superficial basal cell carcinomas (BCCs) to photodynamic therapy (PDT). Release of ALA hydrochloride from a 20% w/w formulation was found to be incomplete and that approximately 36.8% of the total dose is released during the application period of 4 h. Using scintillation spectroscopy and a precise tissue sectioning protocol, it was demonstrated that depths of penetration of at least 2 mm from the lesion surface had been reached. Using cumulative stratal ALA concentrations, it was found that 10% of the total applied dose permeated into the lesion. In spite of this, comparisons drawn with photodynamic concentrations used in tissue culture work reported elsewhere revealed that estimations of the ALA concentration at 2 mm were sufficient to elicit a possible therapeutic response. Results from this work question the reasons given for poor outcomes of PDT in nodular BCC based solely on depth as a hindering factor.
authors.affiliation: Department of Dermatology, Belfast City Hospital, Lisburn Road, Belfast BT9 7AB, Northern Ireland, UK.
authors.forename: Sharareh
authors.initials: S
authors.lastname: Ahmadi
authors.forename: Paul A
authors.initials: PA
authors.lastname: McCarron
authors.forename: Ryan F
authors.initials: RF
authors.lastname: Donnelly
authors.forename: A David
authors.initials: AD
authors.lastname: Woolfson
authors.forename: Kevin
authors.initials: K
authors.lastname: McKenna
mesh_terms: D000368:Aged; D000622:Aminolevulinic Acid / Q000378:metabolism*; D001706:Biopsy; D002280:Basal Cell Carcinoma / Q000378:metabolism* / Q000628:therapy; D002851:Chromatography, High Pressure Liquid; D015925:Cryopreservation; D003879:Dermatologic Agents / Q000494:pharmacology; D004058:Diffusion; D016503:Drug Delivery Systems; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009824:Ointments / Q000494:pharmacology; D010232:Paraffin; D010778:Photochemotherapy / Q000379:methods*; D010865:Pilot Projects; D012824:Silicic Acid; D012878:Skin Neoplasms / Q000378:metabolism* / Q000628:therapy; D013053:Spectrophotometry; D013997:Time Factors
chemical_list: D003879:Dermatologic Agents; D009824:Ointments; C052551:Unguentum Merck; D012824:Silicic Acid; D010232:Paraffin; D000622:Aminolevulinic Acid