Depot preparations/injections release

Leuprolide is available in solution for daily subcutaneous injection and in slow-release depot preparations in which leuprolide is lyophilized in microspheres given by intramuscular injection. 

Estrogen preparations. Depot preparations for Lm. injection are oily solutions of esters of estradiol (3- or 17-OH group). The hydro-phobicity of the acyl moiety determines the rate of absorption, hence the duration of effect. Released ester is hydrolyzed to yield free estradiol. 

The more recent development of a slow-release (depot) formulation of goserelin [81 ] has allowed the administration of the agonist as a single monthly injection. Such a depot preparation has obvious clinical advantages. The peptide was incorporated in a 50 50 lactide-glycolide copolymer in the form of a small cylindrical rod, which can be injected, under local anaesthesia, through a 16-gauge needle, into the subcutaneous tissue of the anterior abdominal wall. 

Somatropin injectable suspension (Nutropin Depot) is a long-acting preparation of rhGH enclosed within biodegradable microspheres. These microspheres degrade slowly after subcutaneous injection such that the rhGH is released over about 1 month. 

Heparin and heparinoids are absorbed in only trace amounts when given in large doses orally . EDTA increases the absorption . Subcutaneous and intramuscular injection of various depot heparin preparations have not been found very satisfactory. They fail to give satisfactory blood levels and they increase Sensitization. With subcutaneous injection, the ability of heparin to become fixed to protein becomes a factor modifying absorption. One of the basic difficulties in deciding on the value of subcutaneous or intramuscular injections of heparin is that there has been no quantitative comparison made of the blood levels of heparin administered in these two ways, to determine how much appears in the circulation in active form. It is possible that much heparin never reaches the circulation. This is to be expected when it is remembered that heparin released by mast cells does not reach the circulation. Depository forms of heparin have been replaced by the use of concentrated heparin solutions (40 gm per cent), so that volumes of 0-2 to 0-4 ml. ean be injected into subcutaneous fat tissue or intramuscularly. 

Fatty acid esters of corticosteroids may be used for the preparation of depot injections, either as oily solutions or aqueous suspensions. The nature of the fatty acid, in particular the length of the carbon chain, determines, to a large extent, its solubility and therefore its release and absorption rate into the bloodstream. In addition, in the case of corticosteroids, solutions or microcrystalline suspensions in either oil or water are used for intra- or periarticular injection. 

Ferguson et al. (1990), at Elanco, prepared various oiFwax depot injectables for sustained release ofbovine somatotropin. To thicken the oils, waxes were melted into the oils, which were then cooled and homogenized until uniform in consistency. Solid BST was dispersed into the viscous oil and wax mixture. Three combinations of BST, oil, and wax were formulated and injected into dairy cattle, and these formulations gave sustained... 

Among the various approaches, major emphasis has been directed toward the development of parenteral repository or depot antimalarial substances. Such preparations consist typically of suspensions of repository compounds in aqueous or lipid vehicles. When these suspensions are injected intramuscularly or subcutaneously, the insoluble material is deposited in the tissues, forming a depot from which active principles are very slowly released into the circulation. In preparations of this type, it is essential that candidate substances be nonirritating to the tissues and imdergo minimal encapsulation. 

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