Carbamazepine drug monitoring

Jerling M, Lindstrom L, Bondesson U, Bertilsson L. Fluvoxamine inhibition and carbamazepine induction of the metabolism of clozapine evidence from a therapeutic drug monitoring service. 

Battino D, Crod D, Rossini A, et al. Serum carbamazepine concentrations in elderly patients a case-matched pharmacokinetic evaluation based on therapeutic drug monitoring data. Epilepsia 2003 44 923-929. 

Another use of the laboratory is for therapeutic drug monitoring (TDM) of psychotropics with defined optimal ranges, narrow therapeutic indices, or both. Although TDM is not essential for many psychotropics, it is for others, including lithium, several TCAs, valproate, and carbamazepine. It may also be helpful to optimize the use of certain antipsychotics (e.g., haloperidol, clozapine) ( 7). 

BaciewiczAM. Carbamazepine drug interactions. Ther Drug Monitor 1986 8 305-317. 

Kintz, R, Marescaux, C., and Mangin, R, Testing human hair for carbamazepine in epileptic patients is hair investigation suitable for drug monitoring. Hum. Exp. Toxicol., 14, 812, 1995. 

TEUTHROMYCIN CARBAMAZEPINE 1 levels of these drugs, with risk of therapeutic failure Induction of hepatic metabolism 1. Avoid co-administration of telithromycin for up to 2 weeks after stopping carbamazepine 2. With the other drugs, monitor for 1 clinical efficacy and t dose as required... 

Vasudev K, Goswami U, Kohli K. Carbamazepine and valproate monotherapy feasibility, relative safety and efficacy, and therapeutic drug monitoring in manic disorder. Psychopharmacology (Berl) 2000 150(l) 15-23. 

Potter JM, Donnelly A. Carbamazepine-10, 11-epoxide in therapeutic drug monitoring. Ther Drug Monit... 

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. 

Therapeutic drug monitoring Anticonvulsants Carbamazepine Phenytoin Ethosuximide Primidone Phenobarbitone Valproic acid... 

The effects of buspirone are decreased when the drug is administered with fluoxetine Increased serum levels of buspirone occur if the drug is taken with erythromycin or itraconazole Should any of these combinations be required, the dosage of buspirone is decreased to 2.5 mg BID, and the patient is monitored closely. Venlafaxine blood levels increase with a risk of toxicity when administered witii MAOIs or cimetidine There is an increased risk of toxicity when trazodone is administered with the phenothiazines and decreased effectiveness of trazodone when it is administered with carbamazepine Increased serum digoxin levels have occurred when digoxin is administered with trazodone There is a risk for increased phenytoin levels when phenytoin is administered witii trazodone... 

Carbamazepine Manufacturer recommends CBC and platelets (and possibly reticulocyte counts and serum iron) at baseline, and that subsequent monitoring be individualized by the clinician (e.g., CBC, platelet counts, and liver function tests every 2 weeks during the first 2 months of treatment, then every 3 months if normal). Monitor more closely if patient exhibits hematologic or hepatic abnormalities or if the patient is receiving a myelotoxic drug discontinue if platelets are less than 100,000/mm3, if white blood cell (WBC) count is less than 3,000/mm3 or if there is evidence of bone marrow suppression or liver dysfunction. Serum electrolyte levels should be monitored in the elderly or those at risk for hyponatremia. Carbamazepine interferes with some pregnancy tests. 

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. 

Isoniazid Carbamazepine, phenytoin Decreased metabolism of other agents (nausea, vomiting, nystagmus, ataxia) Monitor drug SDC... 

Carbamazepine therapy is initiated at 200-400 mg/day in two divided doses, and the typical daily dose is often in the 1000-2000 mg/day range. There are no established plasma levels for carbamazepine specifically established for BEAD, so the levels used in monitoring the drug in the treatment of epilepsy (i.e., 4-12 ig/mL) are typically used. 

Unlike carbamazepine, valproic acid has few drug interactions, an added benefit for elderly patients. One interaction worthy of mention, however, is that aspirin can increase levels of valproic acid. For this reason, vascular dementia patients taking an aspirin a day may need a lower dose of valproic acid or at least more careful monitoring of blood levels when starting valproic acid. 

Carbamazepine is an anti-epileptic, which may also be used in the treatment of trigeminal neuralgia. Monitoring of carbamazepine plasma concentrations is required if high doses are administered as carbamazepine tends to be an autoinducer, meaning that the half-life is shortened following repeated administration of the drug. 

Carbamazepine, phenytoin, pheno-barbital, and other anticonvulsants (except for gabapentin) induce hepatic enzymes responsible for drug biotransformation. Combinations between anticonvulsants or with other drugs may result in clinically important interactions (plasma level monitoring ). 

While regular monitoring of plasma phenytoin levels can result in improved seizure control, the benefit derived from measuring other commonly prescribed anticonvulsant drugs is difficult to assess. Phenobarbitone, primidone, and carbamazepine will be discussed briefly. 

Citalopram (Celexa) [Antidepressant/SSRI] WARNING Closely monitor for worsening depression or emergence of suicidality, particularly in pts <24 y Uses Depression Action SSRI Dose Initial 20 mg/d, may t to 40 mg/d X in elderly hqjatic/renal insuff Caution [C, +/-] Hx of mania, Szs pts at risk for suicide Contra MAOI or w/in 14 d of MAOI use Disp Tabs, cap, soln SE Somnolence, insomnia, anxiety, xerostomia, diaphoresis, sexual dysfxn Notes May cause X Na /SIADH Interactions t Effects W/ azole antifungals, cimetidine, Li, macrolides, EtOH t effects OF BBs, carbamazepine, CNS drugs, warfarin X effects W/ carbamaz ine X effects OF phenytoin may cause fatal Rxn W/ MAOIs EMS Use caution w/ CNS depressants, may need a reduced dose concurrent EtOH... 

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