Tiagabine with carbamazepine

Anticonvulsants. Several antiseizure medicines have been studied in the treatment of PTSD, and some results have been encouraging. Open label studies, first with carbamazepine (800-1200 mg/day) and later with valproate (500-2000 mg/ day), demonstrated overall improvement in PTSD patients, though not for intrusive recollections per se. Recent open label studies of gabapentin, lamotrigine, tiagabine, and topiramate have suggested these anticonvulsants might also be helpful for some PTSD symptoms. 

Other agents with anticonvulsant properties that may be of use m the treatment of bipolar disorder include topiramate, gabapentin, tiagabine and carbamazepine (Janicak et al., 2001). 

Outside of the evidence-based guidelines, other pharmacologic treatments are commonly used or avoided. For initial treatment of absence seizures, ethosuximide and valproate are commonly used, not only in the United Kingdom, but also in the United States. Zonisamide may be also used for initial treatment of absence and myoclonic seizures. In absence and myoclonic seizures, carbamazepine, oxcarbazepine, gabapentin, tiagabine, and pregabalin should be avoided, as they have been associated with an exacerbation of these types of seizures. 

II.e. 5.2. Interactions between first and second generation AEDs. Felbamate raises plasma concentrations of phenytoin, valproic acid and carbamazepine. Clearance of tiagabine, topiramate and zon-isamide is increased in the presence of an enzyme inducer. Vigabatrin reduces phenytoin concentrations after 4-5 weeks of comedication (via an unknown mechanism). For tiagabine, the elimination half-life may be reduced by 2-3 hours in the presence of an enzyme-induction AED. Lamotrigine elimination is slower if given with valproic acid. Topiramate reduces elimination of phenytoin. 

Hogan RE, Bertrand ME, Deaton RL, Sommerville KW. Total percentage body weight changes during add-on therapy with tiagabine, carbamazepine and phenytoin. Epilepsy Res 2000 41(l) 23-8. 

Clearance of tiagabine is increased if taken with an enzyme-inducing antiepileptic drug (e.g., carbamazepine, phenobarbital, phenytoin, primidone) and thus plasma levels are reduced however, no dose adjustments are necessary for treatment ot epilepsy as the dosing recommendations for epilepsy are based on adjunctive treatment with an enzyme-inducing antiepileptic drug... 

Visual field defects associated with various antiepUeptic drugs (carbamazepine, diazepam, gabapentin, pheny-toin, tiagabine, and vigabatrin) have been reviewed (19). The true frequency is unknown, but in a retrospective study in 158 patients with partial epilepsy visual field defects were detected in 21 (13%) 13 patients had concentric visual field constriction without subjective spontaneous manifestations. Of these 13 patients, 9 were taking vigabatrin. 

Three patients had transient dystonic reactions while taking tiagabine 20-30 mg/day in addition to carbamazepine (18). The dystonic reactions occurred during the first few weeks of treatment. The patients each had a different type of dystonia focal limb dystonia, oromandibnlar dystonia, and writer s cramp. In each case the dystonia resolved spontaneously without withdrawal of tiagabine and without any other treatment. Although paroxysmal dystonic movements have been well described with... 

Tiagabine is rapidly absorbed after oral administration, extensively bound to serum or plasma proteins, and metabolized mainly in the liver, predominantly by CYP3A. Its half-life of about 8 hours is shortened by 2 to 3 hours when coadministered with hepatic enzyme-inducing drugs such as phenobarbital, phenytoin, or carbamazepine. 

Complex partial Partial with secondarily Impaired consciousness lasting 30 seconds to 2 minutes, often associated with purposeless movements such as lip smacking or hand wringing. Simple or complex partial seizure evolves into a Carbamazepine, phenytoin, valproate Gabapentin, lamotrigine, levetiracetam, tiagabine, topiramate, zonisamide... 

In an early clinical study, tiagabine was reported to have no significant effect on the plasma levels of carbamazepine, phenytoin, valproate, and vigabatrin. Similarly, tiagabine (titrated from 8 mg up to a maximum of 48 mg daily over 18 days) did not alter the steady-state pharmacokinetics of phenytoin or carbamazepine in 12 patients with epilepsy. However, in another similar study, it reduced the AUC of valproate by 10%, but this reduction is not expected to be elinieally significant. ... 

There is little evidence to suggest that carbamazepine interacts with digoxin, and topiramate causes only a small reduction in digoxin serum levels. Levetiracetam and tiagabine do not appear to interact with digoxin. 

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