In phototoxicity

Sambuco (1985) has described the sunburn response of the Yucatan minipig to ultraviolet (UV) light, suggesting that this species would also make a good model in phototoxicity as well as photocontact dermatitis studies. Thirty 12-cm sites were demarcated, permitting the study of 15 different dermal dosages of UV radiation. 

Loveday KS, Bergman CL. Trends in phototoxicity testing. Drug Cosm Ind 1994 155 30-37. 

Precautions are necessary to avoid ultraviolet radiation after taking photoreactive drugs (38). Metabolism of hn-comycin can lead to the formation of reactive oxygen species and cause tissue injury and damage to various cellular macromolecules, which can result in phototoxicity. Typical photosensitivity with a maculopapular eruption has been observed with hncomycin in two patients treated intramuscularly (6). 

Tests to study phototoxicity and/or photoallergy usually involve 25 subjects with test material bearing patches applied in duplicate one set does not receive radiations while the second set is irradiated. In phototoxicity, patches are applied for 24 h. The irradiated patch is exposed to 16Jcm UVA and 0.75 MED (minimum erythema dose) UVB. All sites are evaluated at 1, 24, 48, and 72 h following exposure. 

Phototoxicity is photosensitivity that is independent of immunological responses. Phototoxic responses are dose dependent and will affect almost anyone when sufficient dosage is applied or when taken concurrent with UV exposure. In phototoxic reactions, photoactivated chemicals cause direct cellular damage. UV absorption produces either excited state chemicals or metabolites of these chemicals. These, in turn, can be converted into either free radicals or singlet oxygen, either of which results in biomo-lecular oxidation)10 ... 

Rash, in areas of the body exposed to UV light, may be indicative of drug phototoxicity. Among the antibacterial agents, the tetracyclines and the sulfonamides are notably phototoxic. More recently, the fluoroquinolones have been implicated in phototoxic responses, and because these antibiotics are widely used, the incidence of this type of adverse effect is increasing. 

Three eudistomins display phototoxicity against several viruses, bacteria, yeast and mammalian cells (201,202) when the natural products are exposed to ultraviolet (UVA) irradiation. The activity appears to diminish with increasing side chain complexity eudistomin N (3) is most active, being similar in phototoxicity to P-carboline and harman. Eudistomins M (13) and O (4) were moderately active while eudistomins H (7) and I (8) were effectively inactive even in the presence of UVA. 

The quantum yield provides information about the effectiveness of a certain photo-induced process. The quantum yield of loss of starting material or product formation will provide valuable information about structure-activity relationships. Fluorescence and phosphorescence quantum yields will indicate the fraction of molecules likely to be found in the excited singlet and triplet state. The quantum yield is a useful parameter to predict the importance of a certain reaction for example, an isolated degradation product can have a long phosphorescence lifetime and should therefore be considered as a possible sensitizer. If the quantum yield of formation of this product is very low, however, it is less likely to be formed in a biologically active concentration and may therefore play a minor role in phototoxicity reactions. 

In phototoxicity testing, lime essential oil processed by expression showed phototoxic effects in pigs and hairless mice, while the steam-distilled oil showed no such effects (Opdyke 1979). 

There are two types of drug reactions by photosensitivity (Harber and Baer 1972). In phototoxicity, the reaction is characterized by epidermal lesions provoked by a... 

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