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Carbamazepine (Tegretol )
Carbamazepine (Tegretol )
Tegretol is the primary antiepileptic drug,effective in the treatment of psychomotor seizures, generalized tonic –clonic seizures and mixed seizures.
Carbamazepine is the drug of choice for treatment of trigeminal and glosspharyngeal neuralgia pain.
The mechanism of action is unclear ;its anticholinergic , muscle relaxant , antiarrythmic, anti diuretic and neuromuscular transmission – inhibitory action may be explained by blockage of neurotransmition reuptake.
Pharmatokinetics:
– After oral administration, it is rapidly absorbed with wide individual variability.
-Time to peak serum concentration : variable , 4-8 hr after dosing with chronic dose , >12 hr after asingle dose , in over dose after 24 hr .
– Time to achieve steady state : after 2-6 days of chronic oral dose .
– Route of elimination 99% by hepatic metabolism ,1%by renal .
– The elimination half life early in therapy is – 1 day .
– With chronic therapy , the elimination half life is reduced to 15 -20 hours.
– Any reduction in liver function results in drug accumulation.
Specimen:
– Serum , 3ml blood in plain tube.
– Sampling time : chronic oral dosing : trough level ; immediately prior to next oral dose . Peak level; approximately 2-4 hours after an oral dose due to variability of absorption , the trough level may not represent the lowest drug level during the dosing interval , so multiple determinations may be necessary in some patients. After beginning therapy with the drug , it requires 2-6 days to reach steady –state levels.
Methodology:
Enzyme immunoassay , FPIA.
Referance range:
– Therapeutic :4- 10 mg\ ml.
– Patients who require higher level ( 8- 12 Mg\ml) should be watched closely . If other anticonvulsants are given therapeutic range is 4-8 mg\ml.
– possible panic range : Toxic > 15 mg \ml ; >8 mg\ml . if multiple drug regimen.
Carbamazepine (Tegretol )
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