Charge transfer complexes of K vitamins with several classes of antimicrobials.

The charge transfer donor (D)-acceptor (A) complexes formed between three classes of vitamin K (all electron acceptors in this study) with several thiazine psychotropes, used also as antimicrobials, antimalarials, antibiotics, and anticoagulants, were studied by means of alternating current titrations. The monochloride thiazines formed 2:1 (D:A) complexes, interacting from 26 to 47.5%; the dihydrochloride formed a 3:1 (D:A) complex. The antimalarials quinine and its isomer quinidine yielded 2:1 (D:A) complexes, interacting 51 and 60%, respectively. Quinacrine did not complex with vitamin K. The antibiotics sulfisoxasole and sulfamethisole gave 1:1 complexes, respectively interacting 6.2 and 11.7%. The anticoagulants warfarin, coumarin and dicumarol, rather than forming complexes proceeded rapidly to chemical reaction. When the above thiazine antimicrobials, antimalarials and antibiotics are present in patients receiving vitamin K post-operatively the dosage of administered vitamin K should be increased to counteract the donor-acceptor interaction effect.