What is the main characteristic of a sustained release medication?

The main characteristic of a sustained release medication is that it is designed to release its active ingredient gradually over an extended period of time. This allows for a prolonged therapeutic effect and can lead to reduced dosing frequency compared to immediate-release formulations. The variation in the amount of time it takes for the medication to dissolve is influenced by the specific formulation and the intended release profile.

Sustained release medications are formulated to control the rate at which the drug is dissolved and absorbed, thus prolonging its action in the body. This characteristic provides a more consistent therapeutic effect and may help in reducing side effects that can occur with peak concentrations of medication.

The other options are incorrect as sustained release medications do not adhere to a fixed time for dissolution (ruling out a fixed time), they can be in solid forms such as tablets or capsules rather than being exclusively liquid, and they are not limited to intravenous administration but can be taken orally or through other routes depending on the formulation.