hours roughly (4 days). A drug must be removed from one system 5.5 times its elimination half-life. Tegretol's elimination half-life varies depending on whether it is a single dosage or repeated administration. The initial half-life ranges from 25 to 65 hours, reducing to 12–17 hours with repeated doses. The average concentration of Tegretol in the blood is approximately 0.5 mg/L 1 hour after oral administration and decreases gradually until it reaches below 0.1 mg/L 7 hours after ingestion. Therefore, if therapeutic levels are needed for several periods during the day, the medication should be taken at different times. Although Tegretol seems to be well tolerated by most patients, certain side effects may occur. Allergic reactions such as skin rashes, hives, itching, cough, shortness of breath, swelling of the face, lips, tongue, or throat can be life-threatening or cause serious illness. If you experience any symptoms of an allergic reaction, contact your doctor immediately. Tegretol can cause nervous system problems such as drowsiness, confusion, irritability, depression, memory loss, headache, dizziness, tremors, and sleep disorders. These conditions can be dangerous if you drive a car or operate machinery. Alcohol consumption may increase these effects further. Discuss potential risks associated with Tegretol treatment with your doctor before beginning any new regimen.