Carbamazepine monitoring therapy with

Why should concurrent therapy with carbamazepine and isoniazid be monitored closely ... 

Oxcarbazepine Hyponatremia (serum sodium concentrations less than 125 mEq/L) has been reported and occurs more frequently during the first 3 months of therapy serum sodium concentrations should be monitored in patients receiving drugs that lower serum sodium concentrations (e.g., diuretics or drugs that cause inappropriate antidiuretic hormone secretion) or in patients with symptoms of hyponatremia (e.g., confusion, headache, lethargy, and malaise). Hypersensitivity reactions have occurred in approximately 25-30% of patients with a history of carbamazepine hypersensitivity and requires immediate discontinuation. 

Before beginning treatment with carbamazepine, liver function tests, a complete blood count with platelets and reticulocytes, and a pregnancy test should be performed. Long-term monitoring of carbamazepine therapy includes periodic assessment of liver function tests, complete blood count, reticulocyte count, and carbamazepine levels. These should be performed every 2 months during the first 6 months of treatment and every 6-12 months thereafter. 

In this context, the first role of the laboratory is to detect specific adverse effects to target organs (see Role of the Laboratory later in this chapter). Monitoring will generally be tailored to the specific therapy used because of its known potential for causing certain problems. Examples include periodic blood counts with carbamazepine or clozapine and thyroid and renal function studies with long-term maintenance lithium. 

PROTON PUMP INHIBITORS CARBAMAZEPINE Possible altered efficacy of carbamazepine Unclear possibly via 1 clearance Use with caution. Monitor carbamazepine levels when starting or stopping therapy, and use the proton pump inhibitor regularly, not PRN. Not reported with pantoprazole or rabeprazole... 

More recently, newer medicines have been used to treat bipolar manic depression disorder. Carbamazepine and valproate are two anticonvulsants that have been particularly useful with patients who do not respond to lithium. These medications also have to be monitored for proper dosages. Antidepressants may be necessary during severe depressive episodes but may push a patient into the manic state. In severe cases, hospitalization and even electroconvulsive therapy (ECT) may be necessary. 

Transient elevations of the serum transaminases occur in 12% to 15% of patients receiving isoniazid and usually occur within the first 8 to 12 weeks of therapy. Overt hep ato toxicity, however, occurs in only 1% of cases. Risk factors for hepatotoxicity include patient age, preexisting liver disease, excessive alcohol intake, pregnancy, and the postpartum state. Isoniazid also may result in neurotoxicity, most frequently presenting as peripheral neuropathy or, in overdose, as seizures and coma. Patients with pyridox-ine deficiency, such as pregnant women, alcoholics, children, and the malnourished, are at increased risk. Isoniazid may inhibit the metabolism of phenytoin, carbamazepine, primidone, and warfarin." Patients who are being treated with these agents should be monitored closely, and appropriate dose adjustments should be made when necessary. 

Callaghan N, Duggan B, O Hare J, O DriscoU D. Serum levels of phenobarbitone and phe-nylethylmalonamide with primidone used as a single d and in combination with carbamazepine or phenytoin. In Johannessen SI et al. Antiepileptic Therapy Advances in Drug Monitoring. New York Raven Press 1980, 307-13. 

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