Depot preparations/injections insulin

Atrophy of subcutaneous fat at the site of insulin injection (lipoatrophy) is probably an immune response to insulin, whereas lipohypertrophy (enlargement of subcutaneous fat depots) is ascribed to the lipogenic action of high local concentrations of insulin. Both problems are rare with more purified preparations. However, hypertrophy may occur with human insulin if patients inject themselves repeatedly in the same site. The recommended treatment is to avoid the hypertrophic areas by using other injection sites and to inject insulin into the periphery of the atrophic sites in an attempt to restore the subcutaneous adipose tissue. 

Apart from foreign sera, the commonest cause is penicillin, in particular depot injection preparations. Sulfonamides, insulin, and barbiturates have also been reported (Hoigne 1966 Hoigne and Doppen 1963 Hoigne and Krebs 1964 Schulz 1972). 

Insulin, whatever its source, may be formulated in a number of ways. This directly affects its activity profile upon administration to diabetic patients. Fast (short)-acting insulins are those preparations that yield an elevated blood insulin concentration relatively quickly after their administration, which is usually by s.c. or, less commonly, by i.m. injection. Slow-acting insulins, on the other hand, enter the circulation much more slowly from the depot (injection) site. This is characterized by a slower onset of action, but one of longer duration (Table 8.4). 

Jet injectors deliver insulin transcutaneously by an air-jet mechanism. The insulin solution or suspension is forced at high pressure through a fine nozzle, penetrates the skin without a needle, and creates a multitude of small depots. The dispersion of insulin deposited in the tissue explains the more rapid absorption of both rapid- and retarded-acting preparations (Taylor et al, 1981 Malone eta/., 1986 Houtzagerse/a/., 1988). Jet injection seems to affect the action profile of NPH insulin more markedly than that of the Lente t e insulins (Houtzagers et al, 1988). These devices are not painless and, in a European study, not well accepted by patients irrespective of the presence or absence of needle phobia (Houtzagers etal, 1988). However, in a more recent American study, the majority of patients preferred to take insulin by jet injector compared to needle injection (Denne et al, 1992). Jet injection has been found to be associated with a diminished antibody... 

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