As a narcotic, hydrocodone relieves pain by binding to opioid receptors in the brain and spinal cord. It can be taken with or without food as desired. When taken with alcohol, it can intensify drowsiness. It may interact with monoamine oxidase inhibitors, as well as other drugs that cause drowsiness. It is in FDA pregnancy category C: its effect on an embryo or fetus is not clearly known and pregnant women should consult their physicians before taking it. Common side effects include dizziness, lightheadedness, nausea, drowsiness, euphoria, vomiting, and constipation. Some less common side effects are allergic reaction, blood disorders, changes in mood, mental fogginess, anxiety, lethargy, difficulty urinating, spasm of the ureter, irregular or depressed respiration and rash.

Hydrocodone is habit-forming, and can lead to physical and psychological addiction; however, the potential for addiction varies from individual to individual depending on unique biological differences. In the U.S., pure hydrocodone and forms containing more than 15 mg per dosage unit are considered Schedule II drugs. Those containing less than or equal to 15 mg per dosage unit in combination with acetaminophen or another non-controlled drug are called hydrocodone compounds and are considered Schedule III drugs. Hydrocodone is typically found in combination with other drugs such as paracetamol (acetaminophen), aspirin, ibuprofen and homatropine methylbromide. The purpose of the non-controlled drugs in combination is often twofold. 1) To provide increased analgesia via drug synergy. 2) To limit the intake of hydrocodone by causing unpleasant and often unsafe side effects at higher than prescribed doses (See Below). In the UK it is listed as a Class A drug under the Misuse of Drugs Act 1971. Hydrocodone is not available in pure form in the United States due to a separate regulation, and is always sold with an NSAID, acetaminophen or an antihistamine. The cough preparation Codiclear DH is the purest US hydrocodone item, containing guaifenesin and small amounts of ethanol as active ingredients. In Germany and elsewhere, hydrocodone is available as single-active-ingredient tablets as Dicodid (by analogy to the original manufacturer's other products Dilaudid and Dinarkon and others) available in 5 and 10 mg strengths.