Abstract: The present invention relates to a tetrahydroisoquinoline derivative represented by the following formula 1 exhibiting an inhibitory action for agglutination caused by fibrinogen, which may be effectively used as an antithrombotic agent or a platelet agglutination-inhibiting agent. The present invention also relates to a medical preparation containing such compound. ##STR1## In formula 1, B and G are an alkylene optionally substituted with an alkyl or the like; D is H, an alkyl, or the like; E is 1,2,3,4-tetrahydroisoquinoline optionally substituted with R.sub.1 to R.sub.4 which binds to G at position 2; R.sub.1 to R.sub.4 are an alkyl or the like; L is hydroxy or the like; and A is a substituent represented by formula (2), and C is carbon. ##STR2## In formula 2, M and R.sub.5 to R.sub.8 are H, an alkyl or the like.

Abstract: Illustrative examples of the N-(3-pyridylalkyl)sulfonamide derivative are represented by the following formulae [II] and [III]: ##STR1## The derivatives are available for a thromboxane A.sub.2 production inhibitor, a thromboxane A.sub.2 antagonist, a prostaglandin H.sub.2 antagonist, an anti-thrombus agent, a thrombus-preventing agent and an anti-allergy agent.