Burroughs Wellcome Co.

David J Livingstone

Richard M Hyde

John Frederick Batchelor

Williasm R King

Tricyclic compounds of formula (I) ##STR1## wherein X.sup.1 is a carboxyl or 5-tetrazolyl group

Tetrazolyl substituted tricyclic compounds and pharmacological

Use of compounds of formula (I) ##STR1## to provide a more effective delivery of oxygen to the tissues of a mammalian, including human, recipient. In vivo applications include the relief or amelioration of conditions wherein there is tissue hypoxia; in vitro the compounds are of use in the storage of mammalian, including human, red blood cells to maintain their oxygen-delivery capacity and prolong their useful storage life. Also provided is a sterile, sealed vessel containing an anticoagulant, a non-toxic amount of a compound of formula (I) and optionally mammalian, in particular human, red blood cells.

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Beckenham, United Kingdom

David J Livingstone