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NURS 615 Exam II

Terms in this set (44)

Carbamazepine is metabolized in the liver and has the unique ability to induce its own metabolism (autoinduction). Due to autoinduction, initial concentrations within therapeutic range may later fall despite good compliance. It also induces the metabolism of many CYP450 enzymes and other substances. Slowly but well absorbed half life of about 30 hours, shortens to 15 hours when given repeatedly

The exact mechanism of action of carbamazepine is not known, but they are thought to affect the sodium channels, slowing influx of sodium in the cortical neurons and slowing the spread of abnormal activity. Carbamazepine exerts its effect by depressing transmission in the nucleus ventralis anterior of the thalamus. This area is associated with the spread of seizure discharge.

•Absorption and Distribution
Carbamazepine is absorbed through the stomach, the suspension being absorbed more quickly than the tablet form. Absorption from the immediate-release tablets is slow and erratic because of its slow water solubility. The drug is highly lipophilic, resulting in high body tissue binding.

•Metabolism and Excretion

Excretion is through feces and urine.

Average blood levels of carbamazepine occur approximately 6 hours after administration. Half-life can be as long as 65 hours with initial dosing, but is typically 12 to 17 hours as administration continues. It is noteworthy that the half-life after a single dose is much longer than the half-life after long-term use. Steady state is attained in 2 to 4 days.
•Most significant risks are cardiac conduction disorder. At highest risk are children and the elderly therefore, baseline ECG and periodic monitoring should be performed. The most common cardiovascular effect is sinus tachycardia due to the inhibition of norepinephrine reuptake and anticholinergic action. Contribute to the slowing of depolarization of the cardiac muscle, contributing to prolongation of the QRS complex and the PR/QT intervals.
Can be cardiotoxic in overdose.

•TCAs have a direct alpha-adrenergic blocking effect and quindine-like effect on the myocardium, they are contraindicated for those with cardiovascular disorders.

•Due to their acetycholine blocking effect they should be used with caution in those who have glaucoma, prostatic hypertrophy, or urinary incontinence.

•Should not be prescribed in combination with MAOIs or individuals who have demonstrated hypersensitivity in this class.

•Pregnancy category C and are excreted in low doses in breast milk. Safety of use in pregnancy is unclear.

•Tardive dyskinesia and neuroleptic malignant syndrome have been reported, and more likely with amoxapine use due to its dopaminergic effect.

•Should be titrated gradually in either direction. Nausea, headache, vertigo, malaise, and nightmares have been noted following abrupt discontinuance of the drug or after large dose decreases.

•Lower seizure thresholds in those with seizure disorder or those taking medications that also decrease seizure threshold.

•Therapeutic and toxic level index is LOW. Great care needs to be taken when prescribing for a person who is depressed and has suicidal ideas.

•APRNs need to be alert for an energizing effect that precedes depressive symptom remission because this may contribute to sufficient activation to follow through with a suicidal plan. Patients need to be monitored on a weekly basis, especially regarding suicidal thoughts and behaviors, and medication should be dispensed in only small amounts until suicidal risk decreases.

•Used in extreme caution in the elderly due to their anticholinergic and norepinephrine effects they contribute to confusion, orthostatic hypotension, and falls.