Photoprotective agents

Note A photostabilizer is also called light stabilizer or photoprotective agent. 

Habib MJ, Asker AF. Photostabilization of doxorubicin hydrochloride with radioprotective and photoprotective agents potential mechanism for enhancing chemotherapy during radiotherapy. J Parenter Sci Technol 1989 43 259-261. 

A.F. Asker, and R. Gragg, Dimethyl sulfoxide as a photoprotective agent for sodium nitroprusside solutions. Drug Dev. Inv. Pharmacol. 9 837-848, 1983. 

Dyes are often used to differentiate between different tablet strengths so their use as photoprotective agents is merely the extension of an old practice. Photofading can result in confusion, leading to incorrect dosing of a drug. The choice of color and its concentration should be done carefully. 

The photolysis of demeclocycline hydrochloride, in the presence and absence of glutathione as a photoprotective agent, was lowest in citrate buffer when compared to acetate or phosphate buffers (76). Table 2 shows the magnitude of this effect. 

Other benzoic acid derivatives also function as effective photoprotective agents. Methylparaben has a photostabilizing effect on solutions of riboflavin (69). Ethyl aminobenzoate significantly enhanced the photostability of menadione in aqueous solutions (107). 

Sodium benzoate was shown by Asker and Harris (108) to be an effective photostabilizer for physostigmine sulfate solutions. The photostability of minoxidil solution is also enhanced by sodium benzoate (48). Figure 17 shows the absorption curves of sodium benzoate and minoxidil. As can be seen in the figure, sodium benzoate absorbs radiation in the same range as minoxidil, thus acting as a photoprotective agent for the drug (109). 

Thiourea and dl-methionine are effective photoprotective agents for solutions of riboflavin (69), tetracycline hydrochloride (71), doxorubicin hydrochloride (77), reserpine (106), and potassium iodide (121). Thiourea enhances the photostability of solutions of minoxidil (48) and furosemide solution (74). Dl-methionine increases the photostability of ascorbic acid solutions (122). 

It is interesting to note that certain antioxidants absorb radiation in a region close to the absorption range of drugs / drug products. Therefore, they may also function as photoprotective agents (filters) by virtue of these two qualities. 

A number of photoprotective agents were found to enhance the photostability of demeclocycline hydrochloride solution exposed to fluorescent radiation from cool white tubes (76). These results are summarized in Table 8. 

Table 8 Effect of Various Photoprotective Agents on the Photodegradation of Dem-eciocyciine Hydrochioride...

Saija A, Tomatino A, Trombetta D, De Pasquale A, Uccela N, Baibuzzi T, PaoUno D, Bonina F (2000) In vitro and in vivo evaluation of caffeic and fendic acids as topical photoprotective agents. Int J Pharm 199 39-47... 

Marine algae hold immense potential to be utilized as photoprotective elements. Proper utilization of this resource would pave a pay for future detonation in the cosmeceutics and medicinal food market. Advanced biotechnological approaches need to be implied to ocean sciences to explore the vast prospective of these photoprotective agents. Strategies need to be formulated for the appropriate usage of the marine algal photoprotective compounds as an answer to the photodamage caused by UVA/UVB or even the xenobiotics. 

Continuous use of daily broad-spectrum topical sunscreen oral photoprotective agents... 

Used sunscreens and their preservatives, vehicles, photoprotective agents (patch tests and photopatchtesting). 

The major finishes for polyester fibers include photoprotective agents and antioxidants, antistatic agents, soil release finishes, antipilling finishes, and flame retardant finishes. Many of these chemicals can be added to the polymer melt prior to spinning. The finishes can also be added topically during dyeing and finishing. 

Excited-state proton transfer has received much attention because of its importance in fundamental aspects of reaction dynamics and also because of the various possibilities for applications, as in, e.g., effective photoprotecting agents [161-165], laser dyes [166-172], photodynamic therapy [173,174], and fluorescence probes for biological molecules [3,175]. In this section, applications of an excited-state intramolecular proton-transfer (ESIPT) system to photoprotecting agents (UV absorbers) are described briefly. 

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