Pharmaceutical dosage unit compositions containing as an active ingredient a compound of the formula ##STR1## wherein R.sub.1 is hydrogen or lower alkyl, R.sub.2, R.sub.4 and R.sub.5, which may be identical to or different from each other, are each hydrogen, lower alkyl, hydroxyl, lower alkoxy, acyloxy, halogen, nitro or --SO.sub.3 H, and R.sub.3 and R.sub.6, which may be identical to or different from each other, are each hydrogen, lower alkyl, hydroxyl, lower alkoxy, acyloxy, halogen, nitro, -...