What is in ivermectin?

Ivermectin is not a single molecule. It’s a mixture of two closely related macrocyclic lactones produced by the fermentation of the bacterium Streptomyces avermitilis:

- The two main components are ivermectin B1a (~80%) and ivermectin B1b (~20%).

The drug you buy also contains inactive ingredients (excipients) that vary by the dosage form and brand. For example:
- Some oral tablets/suspensions may include lactose, microcrystalline cellulose, povidone, magnesium stearate, etc.
- Topical forms may include emulsifiers, waxes, petrolatum, oils, and preservatives.

The exact list of ingredients is on the product labeling. If you tell me the specific product (brand or form), I can look up its inactive ingredients.

Why this matters: the active component (B1a and B1b) is what provides the antiparasitic effect by targeting invertebrate nerve/muscle receptors; the excipients are there for stability, taste, texture, etc. If you’re asking about this for a medical reason, I can also summarize how ivermectin works and safety considerations.