What is Dihydrocodeine? Dihydrocodeine is a medication composed of opioid pain relievers, aspirin, and caffeine. Some patients who begin using dihydrocodeine for the first time may notice side effects of the medication. Common side effects of dihydrocodeine include nausea, vomiting, upset stomach, tremors, constipation, dry mouth, lightheadedness, dizziness, and drowsiness. In most situations, these common side effects will subside after your body adjusts to the drug. If you experience these common dihydrocodeine side effects for a long time after beginning the medication or if these symptoms worsen, mention this to your doctor or pharmacist. There are also serious side effects associated with dihydrocodeine, although they are relatively uncommon. Serious side effects of dihydrocodeine include agitation, hallucinations, mood changes, irregular heartbeat, increased thirst or urination, ringing in the ears, easy bruising or bleeding, signs of infection, persistent sore throat, fever, heartburn, discomfort when swallowing, dark urine, yellowing of the skin or eyes, signs of kidney problems, difficulty urinating, loss of appetite, unusual tiredness and weight loss. Be sure to notify your doctor if you notice any of these signs. Seek medical attention as soon as you can if you experience fainting, seizure, black stool, severe stomach or abdominal pain, vomit that resembles coffee grounds, slurred speech, and weakness after taking your dihydrocodeine dose.