A sustained release pharmaceutical product comprises a medicinally-active substance in combination with a carboxy alkyl benzyl dextran.  The dextran derivative is preferably a carboxymethyl benzyl dextran having a high benzyl degree of substitution (D.S) and a relatively low carboxyl D.S. obtained by treating dextran in water at 40 DEG C. with sodium monochloroacetate and subsequently with benzyl chloride using a ratio of 3:1 to 6:1 of the chloride to the substituted dextran.  It may be used in a proportion between 1 and 50% by weight of the pharmaceutical product.  Medicaments which may be combined with the substituted dextran are amphetamine hydrochloride, penicillin, streptomycin, chloroprophenyridamine, meperidine, codeine, ephedrine, quinine, quinidine, nicotine, cinchonidine, apmorphine, strychnine, scopolamine or atropine.  Inert fillers such as terra alba and starch; and antihistamines, barbiturates, glycols, soya bean oil, sesame oil, hydrogenated peanut oil and a mixture of oils with beeswax may also be added.  The pharmaceutical product may be used as a dry powder or mixed with liquids to form pastes or wax-like masses, compressed into tablets, pills or pellets or packaged into dry-filled or soft elastic capsules, or sealed into ampoules, or administered in liquid form by intravenous, intramuscular, sublingual, subcutaneous, rectal, intraspinous or intrathecal injection or infused into the vaginal or urinary tract.ALSO:A sustained release pharmaceutical product comprises a medicinally-active substance in combination with a carboxy alkyl benzyl dextran.  The dextran derivative is preferably a carboxymethyl benzyl dextran having a high benzyl degree of substitution (D.S.) and a relatively low carboxyl D.S. obtained by treating dextran in water at 40 DEG C. with sodium monochloroacetate and subsequently with benzyl chloride using a ratio of 3:1 to 6:1 of the chloride to the substituted dextran.  It may be used in a proportion between 1 and 50% by weight of the pharmaceutical product. Medicaments which may be combined with the substituted dextran include penicillin and streptomycin, which form salts with the dextran derivative.ALSO:A sustained release pharmaceutical product comprises a medicinally-active substance in combination with a carboxy alkyl benzyl dextran.  The destran derivative is preferably a carboxymethyl benzyl dextran having a high benzyl degree of substitution (D.S.) and a relatively low carboxyl D.S. obtained by treating dextran in water at 40 DEG  C. with sodium monochloroacetate and subsequently with benzyl chloride using a ratio of 3 : 1 to 6 : 1 of the chloride to the substituted dextran.  It may be used in a proportion between 1 and 50% by weight of the pharmaceutical product. Medicaments which may be combined with the substituted dextran are amphetamine hydrochloride penicillin, streptomycin, chloroprophenyridamine, meperidine, codeine, ephedrine, quinine, quinidine, nicotine, cinchonidine, apomorphine, strychnine, scopolamine or atropine.  Inert fillers such as terra alba and starch; and antihistamines, barbiturates, glycols, soya bean oil, sesame oil, hydrogenated peanut oil and a mixture of oils with beeswax may also be added.  The pharmaceutical product may be used as a dry powder or mixed with liquids to form pastes or wax-like masses, compressed into tablets, pills or pellets or packaged into dry-filled or soft elastic capsules, or sealed into ampoules, or administered in liquid form by intravenous, intramuscular, sublingual, subcutaneous, rectal, intraspinous or intrathecal injection or infused into the vaginal or urinary tract.