Injectable Drug Delivery Development Services

Parenteral routes deliver a drug by injection rather than through the digestive tract. They include intravenous, intramuscular, subcutaneous, and intradermal injection, as well as specialized routes such as intravitreal injection into the eye. Each route differs in the volume it can accept, the onset and duration it supports, and the formulation constraints it places on concentration, tonicity, and viscosity.

An injectable drug must stay in solution at physiological pH, because precipitation after administration can cause venous irritation, phlebitis, and hemolysis. When a compound is poorly soluble, formulators use pH adjustment, co-solvents, surfactants, or solubilizers such as cyclodextrins to reach the required concentration while keeping the product physically and chemically stable.

A depot injectable forms a reservoir at the injection site that releases the drug slowly over weeks to months, which reduces how often a patient must be dosed. These products are commonly built from biodegradable PLGA or PLA microspheres, and their release profile is controlled by factors such as polymer composition, particle size, drug loading, and porosity.

Subcutaneous injection volume is limited, so delivering a high dose in a small volume often requires concentrations above 100 milligrams per milliliter, especially for antibodies and other proteins. At those concentrations, viscosity rises sharply and aggregation becomes more likely, which can affect stability, manufacturability, and whether the product can be pushed through a syringe and needle.

Drugs reach the posterior segment of the eye mainly through intravitreal injection, because the blood-ocular barriers limit what eye drops and systemic routes can deliver to the retina. To reduce the burden of frequent injections, sustained-release formulations and inserts are developed to extend the interval between doses.