Gabapentin half-life

Gabapentin Modulate calcium channels and enhance GABA activity Loading dose Not recommended due to short half-life Maintenance dose 900-3600 mg/day in 3-4 divided doses (doses up to 1 0,000 mg/day have been tolerated) Half-life Not established 5-7 hours (proportional to creatinine clearance) Apparent volume of distribution 0.6-0.8 L/kg Protein binding less than 10% Primary elimination route Renal Drowsiness, sedation Peripheral edema, weight gain... 

The bioavailability of gabapentin is dose dependent Half-life depends on renal function. 

Tiagabine has an elimination half-Ufe of 7 to 9 hours. In patients receiving CyP 3A4 inducing anti-epileptic drugs (AEDs), the elimination half-life decreases to 4 to 7 hours. Phenytoin, phenobarbital, and carbamazepine are CyP 3A4 inducers. Valproic acid and gabapentin are not. Tiagabine is not considered to be a CyP 3A4 inducer. ... 

Gabapentin is absorbed after oral administration and is not metabolized in humans. It is not bound to plasma proteins. It is excreted unchanged, mainly in the urine. Its half-life, when it is used as monotherapy, is 4 to 6 hours. It has no known interactions with other antiseizure drugs. 

There is some evidence that the half-life of felbamate may be prolonged by gabapentin. 

It would seem therefore that no dosage adjustments are normally needed if gabapentin is added to treatment with most of these antiepileptics. However, if gabapentin is added to pbenytoin it may be wise to bear the possibility of raised pbenytoin levels in mind. For mention that gabapentin may prolong the half-life of felbamate, see Felbamate + Gabapentin , p.540. For mention of the lack of interaction between levetiracetam and gabapentin, see Levetiracetam + Other antiepileptics , p.543. 

A patient with end-stage renal disease developed an encephalopathy a few days after taking gabapentin in usual adult doses. Gabapentin is excreted unchanged in the urine and its half-life, normally 5-9 hours, increases to up to 132 hours in anuria [114" ]. 

Drug formulatious Gabapentin has a short half-life and a saturable mechanism of absorption, with consequent lack of proportionality between doses and concentrations. New formulations have therefore been developed. An extended-release formulation may overcome the problems of saturable absorption and short half-life. When administered with a meal, this formulation gradually expands and releases the drug to the upper gastrointestinal tract over an extended period of time. This enables it to be taken once or twice a day compared with three times a day or more for immediate-release gabapentin. 

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