Oil-based injectable solutions and injectable drug suspensions. Conventional long-acting injections consist either of lipophilic drugs in aqueous solvents as suspensions or of lipophilic drugs dissolved in vegetable oils. The administration need for these long-acting formulations only takes place every few weeks or so. In the suspension formulations, the rate-limiting step of drug absorption is the dissolution of drug particles in the formulation or in the tissue fluid surrounding the drug formulation
. Poorly water-soluble salt formations can be used to control the dissolution rate of drug particles to prolong the absorption, and olanzapine pamoate is an example of a poorly water-soluble salt form of olanzapine.
Certain drugs for long-acting formulations are synthesized by esterification of the parent drug to a long-chain fatty acid. Based on its extremely low water solubility, a fatty acid ester of a drug dissolves slowly at the injection site after IM injection and is hydrolyzed to the parent drug. Once the ester is hydrolyzed intramuscularly, the parent drug becomes available in the systemic circulation. The release rate of paliperidone palmitate from long-acting injectable suspension is governed by this mechanism. In many formulations, a fatty acid ester of a drug is used to prepare an oil-based parenteral solution, and the drug-release rate from solution is controlled by the drug partitioning between the oil vehicle and the tissue fluid and by the drug bioconversion rate from drug esters to the parent drug. However, several other factors such as
injection site, injection volume, the extent of spreading of the depot at the injection site, and the absorption and distribution of the oil vehicle per se might affect the overall pharmacokinetic profile of the drug. Decanoic acid esters of antipsychotic drugs are widely used for these oil-based IM injections.
A review on the current status of long-acting injectables, including commercially marketed products. This article is part of a special Drug Delivery issue.
www.pharmtech.com
Maybe you can clarify that for me. Seems to me they are designed that way.
Also it's pretty obvious there is no scientific evidence of IM anabolic steroids precipitating after injection. Who would even study that?
Corticosteroids are not anabolic steroids, but there is evidence of drugs crystallization post injection. Therefore it seems pretty logical to make the assumption that it's a least a possibility.
I'm don't make any steroids myself, but it's my understanding that the solvents are what allow the drugs to be dissolved at a certain concentration. It would be pretty easy to assume the first thing to be absorbed from an IM anabolic steroid injection is the solvent. Leaving you with an oil depot and containing a steroid which can not be held at that concentration.
Just my thoughts.