percentage of injected dose entering hepatocytes is higher than that measured after administration of low molecular weight conjugates 3 high molecular weight conjugates are also devoid of acute toxicity and after repeated intramuscular or intravenous administration do not induce antibodies 4 due to their high solubility more than 150 mg ml and heavy drug load a pharmacologically active dose could be administered in a small volume well compatible with the intramuscular route these conjugates were prepared using a poly l lysine hbr with a molecular weight of 30 70 000 and a polymerization degree of 145 335 sigma as in the preparation of low molecular weight poly l lysine conjugates drugs were coupled via the imidazolate of their phosphoric esters and lactose was linked by reductive amination in the presence of nabh 3 cn however the procedure was modified the ph temperature length of reaction time as well as the imidazolate concentration were all increased in the drug conjugation step moreover lactosamination was performed before drug coupling since at high ph high molecular weight poly l lysine precipitated unless a part of u03b5 nh 2 groups were substituted with galactose residues reductive lactosamination of u03b5 nh 2 groups was carried out by dissolving 200 mg poly l lysine in 20 ml 0 4 m potassium phosphate buffer ph 7 together with 800 mg l lactose and 500 mg nabh.