Quinolizidines are not typically referred to in the context of medical definitions. They are a type of organic compound that consists of a fully saturated, nitrogen-containing ring structure with eight members. These compounds are primarily found in certain plants, particularly in the Leguminosae family (also known as Fabaceae or the pea family).

Quinolizidine alkaloids are natural substances produced by these plants and can have various pharmacological effects on animals and humans. Some of these alkaloids may have medicinal properties, while others can be toxic. For instance, some quinolizidine alkaloids found in plants like lupines can cause poisoning if ingested in large quantities.

While not a medical definition per se, it is worth noting that quinolizidines might appear in the context of pharmacology or toxicology due to their presence in certain medicinal plants and potential effects on human health.

Indolizidines are a type of heterocyclic organic compound that contains a five-membered ring fused to a six-membered ring, with one nitrogen atom and one carbon atom common to both rings. The structure of indolizidine is similar to that of the naturally occurring alkaloids, which are found in various plants and animals and have diverse biological activities.

Indolizidines can be synthesized in the laboratory and have been studied for their potential therapeutic uses, such as anti-inflammatory, antiviral, and insecticidal properties. However, they can also have toxic effects and may interact with other drugs or chemicals in the body.

It is important to note that indolizidines are not a medical term per se, but rather a chemical classification of a specific type of organic compound.