The LD50 (lethal dose 50) of ibuprofen refers to the dose at which 50% of a test population would die as a result of the substance. While the specific LD50 value for ibuprofen is not mentioned in the provided sources, we can still gather some information related to its toxicity.

Ibuprofen is a widely used nonsteroidal anti-inflammatory drug (NSAID) that is commonly used for pain relief and reducing inflammation. It is available both over-the-counter and in prescription-strength formulations. The drug works by inhibiting the production of certain chemicals in the body that cause pain and inflammation.

According to the Drug Patent Watch website, which provides information on drug patents, the patent for ibuprofen expired in 1984. This suggests that the drug has been on the market for several decades and is considered safe for use when taken as directed.

The AAT Bioquest website, which provides information on toxicity, mentions that the LD50 value is commonly used to measure the toxicity of a substance. However, it does not provide the specific LD50 value for ibuprofen.

The National Center for Biotechnology Information (NCBI) book titled "Toxicology in the Middle Ages and Renaissance" provides a historical perspective on toxicology. While it mentions the use of ibuprofen in modern medicine, it does not provide specific information on the LD50 value.

In conclusion, the specific LD50 value for ibuprofen is not mentioned in the provided sources. However, based on the information available, it can be inferred that ibuprofen is generally considered safe when taken as directed. It is important to follow the recommended dosage and consult a healthcare professional if there are any concerns about its use.

Sources:
[1] Drug Patent Watch: https://www.drugpatentwatch.com/p/tradename/IBUPROFEN
[2] AAT Bioquest: https://www.aatbio.com/resources/toxicity-lethality-median-dose-td50-ld50/ibuprofen
[3] NCBI Bookshelf: https://www.ncbi.nlm.nih.gov/books/NBK526078/