As explained by Merck, the time needed for a drug to be excreted out of the system is determined by its half-life and the administered dose. According to Drugs.com, a 10/500 mg dose of the pain relief drug Lortab is out of the system within 24 hours after use.
Lortab is a combination of an opioid called hydrocodone, with a half-life of 3.5 to 4.1 hours, and acetaminophen, which increases the effect of hydrocodone and has a half-life of between 1.25 and 3 hours. However, as mentioned by Drugs.com, Lortab interacts with a range of other medications, which can cause slower elimination of the drug. Since Lortab is metabolized in the liver and excreted with urine, renal and hepatic conditions can also cause the drug to stay in your system longer than expected.