Hydrocodone is a doctor Suggested Pain Relief medicine. It is used to treat severe pain. Hydrocodone is used for a short term period, use it in a long time period can cause effects on the body. Hydrocodone 5-325 mg Side Effects Nausea, Vomiting, Headache, Drowsiness, Stuffy nose, Sneezing, Weakness in the body, Skin allergies, Anxiety, Weight loss, Hiccups, Upset stomach, Fever, Urine problem, Belching, Pain in the muscles, Irregular heart rate.. Do not use this medicine for normal pain. Always contact a doctor before using this medicine.