Vicodin can be habit-forming. If you take this drug over a long period of time, you can become mentally and physically dependent on it, and you may find the drug no longer works for you at the prescribed dosage.

Vicodin may make you drowsy, less alert, or unable to function well physically. Do not drive a car, operate machinery, or perform any other potentially dangerous activities until you know how this drug affects you.

Use caution in taking Vicodin if you have a head injury. Narcotics tend to increase the pressure of the fluid within the skull, and this effect may be exaggerated by head injuries. Side effects of narcotics can interfere in the treatment of people with head injuries.

Use Vicodin with caution if you have a severe liver or kidney disorder, an underactive thyroid gland, Addison's disease (a disease of the adrenal glands), an enlarged prostate, or urethral stricture (narrowing of the tube carrying urine from the bladder).

Older adults and those in a weakened condition should be careful using this drug, since it contains a narcotic. Narcotics such as Vicodin may interfere with the diagnosis and treatment of people with abdominal conditions.

Hydrocodone suppresses the cough reflex; therefore, be careful using Vicodin after an operation or if you have a lung disease.

High doses of hydrocodone may produce slowed breathing; if you are sensitive to this drug, you are more likely to experience this effect.