Along with its needed effects, hydrocodone may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention. Although not all of these side effects may occur, if they do occur they may need medical attention. The manufacturer's product labeling should always be consulted for a list of side effects most frequently appearing in patients during clinical studies. Find information about common, infrequent and rare side effects of Vicodin Oral. hydrocodone is the generic equivlent to Vicodin, Lortab, Lorcet and a few others. The common side effects are drowsiness, nausea, vomiting, etc. I have been taking between 90 and 120 mg of hydrocodone a day and I have been having the most horrifying dreams. I AM NOT having dreams about doing drugs, or getting drugs, and I am ON THE DRUGS when I have them, and they are more like night terrors than nightmares. Fatal side effects can occur if you use opioid medicine with alcohol, or with other drugs that cause drowsiness or slow your breathing. Before taking this medicine You should not use hydrocodone if you are allergic to it, or if you have: Find information about common, infrequent and rare side effects of Hydrocodone-Acetaminophen Oral. Hydrocodone can produce many side effects that differ in severity, depending on the individual and the dosage. Common side effects include drowsiness, gastrointestinal issues, and blurred vision. Potential Side Effects of Hydrocodone The body develops a tolerance to hydrocodone very quickly, which means a user will need larger and more frequent doses to feel the desired effects. Escalating use increases the likelihood and severity of addiction, and it may also cause any of the following side effects. SIDE EFFECTS. VICOPROFEN (hydrocodone and ibuprofen) was administered to approximately 300 pain patients in a safety study that employed dosages and a duration of treatment sufficient to encompass the recommended usage (see DOSAGE AND ADMINISTRATION).