Advil is a brand name for the drug ibuprofen, which is a nonsteroidal anti-inflammatory drug (NSAID) used to treat pain and inflammation. According to Drug Patent Watch [1], the patent for Advil expired in 1984, which means that generic versions of ibuprofen are also available.

The duration of Advil's effectiveness varies depending on several factors such as the dose, individual metabolism, and the severity of the pain. As per Rogers Pharm [2], the effects of Advil usually start within 30 minutes to an hour after taking it and can last for about four to six hours. The drug is absorbed quickly into the bloodstream and reaches peak concentration within one to two hours after taking it.

Drugs.com [3] also states that the duration of Advil's effectiveness depends on the dose. A lower dose of Advil (200-400mg) may provide pain relief for four to six hours, while a higher dose (600-800mg) may last up to eight hours. It is important to follow the recommended dosage and not exceed the maximum daily dose of 1200mg for over-the-counter Advil.

In conclusion, the duration of Advil's effectiveness varies depending on several factors, including the dose, individual metabolism, and the severity of the pain. On average, Advil can provide pain relief for four to six hours, but a higher dose may last up to eight hours. It is important to follow the recommended dosage and not exceed the maximum daily dose of 1200mg for over-the-counter Advil.

Sources:
[1] https://www.drugpatentwatch.com/p/tradename/ADVIL
[2] https://rogerspharm.com/how-long-does-advil-last-on-an-average/
[3] https://www.drugs.com/medical-answers/long-ibuprofen-work-3571994/