Abstract: 5H-pyrido[2',1':2,3]imidazo[4,5-b]indoles of the formulae ##STR1## their pharmaceutically acceptable acid addition salts and the corresponding compounds bearing one or more halogens and/or lower-alkyl groups on the available ring carbon atoms are administered in cholinomimetic amounts to mammals with low acetylcholine or cholinergic activity to ameliorate the symptoms associated with that condition.

Abstract: Pharmaceutical composition for chelating excess iron in a mammal and facilitating the removal of excess iron from the mammalian body are disclosed which comprise as active ingredient an iron-chelating agent selected from the group consisting of 5H-pyrimido(2',1':2,3)imidazo(4,5-b)indole having the formula ##STR1## 5H-pyrido(2',1':2,3)imidazo(4,5-b) indole having the formula ##STR2## or lower alkyl and/or halogen substituted derivatives thereof and pharmaceutically acceptable acid addition salts thereof. Furthermore the preparation of novel 5H-pyrimido(2',1':2,3)imidazo(4,5-b)indoles and intermediates thereof are disclosed.

Abstract: Compounds of the formula: ##STR1## and pharmaceutically acceptable acid addition salts thereof wherein R, R.sub.1, R.sub.2, R.sub.3, are selected from the group consisting of hydrogen, halogen and lower-alkyl of from one to four carbon atoms, inclusive; with the proviso that taken together they constitute the following substituents on the tetracydic ring, 10-halo, 8,10-dihalo, 8,9-di-lower-alkyl, and 7,9-dilower-alkyl; R', R'.sub.1, R'.sub.2, and R'.sub.3 are selected from the group consisting of hydrogen, halogen and lower alkyl of from one to four carbon atoms, inclusive, with the proviso that when taken together they constitute the following substituents, 1-halo, 2-halo, 3-halo, 4-halo, 1-lower-alkyl, 2-lower-alkyl, 3-lower-alkyl, 4-lower-alkyl, 1,3-dihalo, 2,3-dihalo, 2,4-dihalo, 3,4-dihalo, 1,3-di-lower-alkyl, 2,3-di-lower-alkyl, 1,4-di-lower-alkyl; R.sub.4, R.sub.5, R.sub.6, and R.sub.

Abstract: Compounds of the formula: ##STR1## AND PHARMACEUTICALLY ACCEPTABLE ACID ADDITION SALTS THEREOF WHEREIN R, R.sub.1, R.sub.2, R.sub.3, are selected from the group consisting of hydrogen, halogen and lower-alkyl of from one to four carbon atoms, inclusive; with the proviso that taken together they constitute the following substituents on the tetracyclic ring, 10-halo, 8,10-dihalo, 8,9-di-lower-alkyl, and 7,9-dilower-alkyl; R', R'.sub.1, R'.sub.2, and R'.sub.3 are selected from the group consisting of hydrogen, halogen and lower alkyl of from one to four carbon atoms, inclusive, with the proviso that when taken together they constitute the following substituents, 1-halo, 2-halo, 3-halo, 4-halo, 1-lower-alkyl, 2-lower-alkyl, 3-lower-alkyl, 4-lower-alkyl, 1,3-dihalo, 2,3-dihalo, 2,4-dihalo, 3,4-dihalo, 1,3-di-lower-alkyl, 2,3-di-lower-alkyl, 1,4-di-lower-alkyl; R.sub.4, R.sub.5, R.sub.6, and R.sub.

Abstract: Compounds of the formula: ##STR1## AND PHARMACEUTICALLY ACCEPTABLE ACID ADDITION SALTS THEREOF WHEREIN R, R.sub.1, R.sub.2, R.sub.3, are selected from the group consisting of hydrogen, halogen and lower-alkyl of from one to four carbon atoms, inclusive; with the proviso that taken together they constitute the following substituents on the tetracyclic ring, 10-halo, 8,10-dihalo, 8,9-di-lower-alkyl, and 7,9-dilower-alkyl; R', R'.sub.1, R'.sub.2, and R'.sub.3 are selected from the group consisting of hydrogen, halogen and lower alkyl of from one to four carbon atoms, inclusive, with the proviso that when taken together they constitute the following substituents, 1-halo, 2-halo, 3-halo, 4-halo, 1-lower-alkyl, 2-lower-alkyl, 3-lower-alkyl, 4-lower-alkyl, 1,3-dihalo, 2,3-dihalo, 2,4-dihalo, 3,4-dihalo, 1,3-di-lower-alkyl, 2,3-di-lower-alkyl, 1,4-di-lower-alkyl; R.sub.4, R.sub.5, R.sub.6, and R.sub.