PHOTO-CHEMICAL DECOMPOSITION OF 1,4-BENZODIAZEPINES - NITRAZEPAM

Abstract— The photochemical activity of nitrazepam, a drug of which phototoxic effects are known, is investigated. Nitrazepam decomposes photochemically in an oxygen‐poor medium, while it is relatively stable in the presence of oxygen. It appears that this quenching of excited nitrazepam by molecular oxygen leads to the formation of singlet oxygen. This is demonstrated in three different ways: 1. In the presence of 2‐methyl‐2‐pentene as acceptor of singlet oxygen, two characteristic products are formed: 2‐methyl‐1‐penten‐3‐ol and 2‐methyl‐3‐penten‐2‐ol. 2. The photosensitized oxidation of L‐dopa in the presence of nitrazepam is increased when D2O, instead of H2O, is added to the solvent system, due to the longer lifetime of singlet oxygen in D2O. 3. The β‐value, the ratio of the rate of decay of singlet oxygen to its rate of reaction, is determined with L‐dopa as acceptor of singlet oxygen. The same value is obtained with both nitrazepam and methylene blue, a known singlet oxygen generator. Copyright © 1979, Wiley Blackwell. All rights reserved