Carbidopa is an unusual medicine, because it has no useful medical effects when taken alone, but when taken in conjunction with another medication like levodopa, it helps this medicine to work better. Therefore, carbidopa side effects are typically only some of the possible effects when using the combination treatment. The commonest side effects of carbidopa alone include gastrointestinal tract problems, problems sleeping and mental confusion.
Typically, carbidopa forms part of a treatment plan for people who have Parkinson's Disease. This condition causes stiffness and tremors to develop in the body, as a result of abnormally low levels of a brain chemical called dopamine. Levodopa is a drug that the body can convert into dopamine, and thereby relieve some of the symptoms of the disease. Carbidopa reduces the breakdown of levodopa in the body and makes the drug more effective. It may be taken as a tablet along with a levodopa tablet, or it may be present in one tablet with the other drug.
Considering the two drugs are commonly used together, carbidopa side effects should be looked at in the context of levodopa side effects. Patients must assess the risks of both drugs separately as well as together. The digestive tract is commonly affected by carbidopa side effects, with a variety of problems related to the drug. A person who takes the drug can experience alterations in taste sensation, a drying of the mouth, and a reduction of normal appetite.
Nausea can occur in the stomach, and the patient can also vomit while taking carbidopa. Both constipation and diarrhea have been noticed as carbidopa side effects, and the drug carries an increased risk of urinary tract infections. Mental symptoms can also occur, and the patient can become confused. Normal sleep patterns can be disrupted by the treatment, and the person can also feel drowsy. Dizziness is another possible carbidopa side effect, as is headache.
If the person is also taking levodopa, which is usual, he or she can also experience muscle twitches or a reduction in muscle tone. Bad dreams can occur, and the person may also experience hallucinations or depression. Patients may lose weight, or be more prone to upper respiratory infections. Serious side effects, though uncommon, include allergic reaction, jaundice and suicidal thoughts. These problems, or those common severe effects, like confusion, necessitate medical examination.