| Definition: |
The sodium salt of porfimer. The purified component of haematoporphyrin derivative, it consists of a mixture of oligomeric porphyrins formed by ether and ester linkages of up to eight porphyrin units (n = 0-6), where R = CH(OH)Me and/or CH=CH2. After addition of hydrochloric acid and/or sodium hydroxide to pH 7.2 - 7.9, it is used as a photosensitiser in photodynamic therapy of non-small cell lung cancer, oesophageal cancer, and superficial bladder cancer. The drug is administered by slow intravenous injection and accumulates in malignant tissue. After 40-50 hours, it is activated by laser light at 630 nm, delivered to the tumour using a fibre optic guide. Subsequent spin transfer to oxygen molecules within the tissue, generates highly reactive singlet oxygen, and subsequent radical reactions generate superoxide and hydroxyl radicals. Propagation of radical reactions ultimately kills the tumour cells. |