Abstract: Xanthines of the general formula: ##STR1## wherein R.sup.1 represents a straight or branched chain alkyl, alkenyl or alkynyl group of 3-6 carbon atoms, and R.sup.2 and R.sup.3, which may be the same or different, each represent hydrogen or halogen or a methyl, methoxy, nitro or trifluoromethyl group or R.sup.2 and R.sup.3 together form a methylenedioxy or ethylenedioxy group; with the proviso that R.sup.2 and R.sup.3 are not both hydrogen; and pharmacologically acceptable salts thereof with an alkali metal base or a nitrogen base containing organic base, are bronchodilators making them of value in treating asthma and vasodilators making them of interest in treating angina, hypertension, congestive heart failure and multi-infarct dementia. The compounds are also of use in combatting other conditions where inhibition of PDE type IV is thought to be beneficial.

Abstract: The present invention relates to the use of 6-[4-(N.sup.3 -methyl-N.sup.2 -cyanoguanidino)phenyl]-5-methyl-4,5-dihydro-3-(2H)-pyridazinone in a method of treating or preventing cardiac arrhythmias.