per os

Definition

By way of the mouth; orally. A route of administration in which a substance is introduced directly into the digestive tract by ingestion, as opposed to injection, topical application, or other delivery methods. In entomology and arachnology, per os administration is used in experimental toxicology, pharmacology, and pathogen transmission studies to deliver compounds or infectious agents to test organisms, often via treated food, droplets, or force-feeding techniques.

Etymology

Latin per ('through') + ōs ('mouth')

Example

In a bioassay of Bacillus thuringiensis toxicity, neonate lepidopteran larvae were dosed per os by placing treated leaf discs in rearing cups, allowing the caterpillars to ingest the endotoxin naturally during feeding.

Synonyms

• PO
• orally

Related Terms

• force-feeding
• toxicology
• Bioassay
• gavage
• nil per os
• enteral

Usage Notes

The abbreviation PO is common in clinical and laboratory notes. Contrast with per rectum, percutaneous, parenteral, and topical routes. In arthropod studies, 'per os' specifically distinguishes oral ingestion from contact exposure or injection methods; precise documentation of dose volume and concentration is essential for reproducibility.