Gabapentin dosing

A single controlled study of gabapentin demonstrated modest effectiveness. A high gabapentin dose, 3600 mg/day, was required to achieve this modest degree of success. Similarly, high dose pregabalin (600 mg/day) was effective in a recent controlled study for social anxiety disorder. 

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... 

Gabapentin, a non-benzodiazapine GABA analog, was modestly effective in a 14-week controlled trial in SAD. Most patients were titrated to a maximal dose of 3600 mg/day.58 Pregabalin 600 mg/day was effective for social anxiety, fear, and avoidance behavior in a 10-week controlled trial.63 Pregabalin was well tolerated, and the most common side effects were somnolence and dizziness. 

If symptoms are not resolved, increase the dose of DA agent or add another agent such as gabapentin or a hypnotic benzodiazepine. 

Peripheral neuropathy is the most common complication reported in type 2 DM. This complication generally presents as pain, tingling, or numbness in the extremities. The feet are affected more often than the hands and fingers. A number of treatment options have been tried with mixed success. Current options include pregabalin, gabapentin, low-dose tricyclic antidepressants, duloxetine, venlafaxine, topiramate, non-steroidal anti-inflammatory drugs, and topical capsaicin. 

BH Stewart, AR Kugler, PR Thompson, NN Bock-brader. A saturable transport mechanism in the intestinal absorption of gabapentin is the underlying cause of the lack of proportionality between increasing dose and drug levels in plasma. Pharmaceut Res 10 276-281, 1993. 

The dose of gabapentin should be started at 600-900 mg/day in two or three doses per day. The usual effective dose is 900-4800 mg/day. Laboratory monitoring is not needed when prescribing gabapentin. It is well tolerated with the most common side effects being drowsiness and headache. 

Postherpetic neuralgia In adults with postherpetic neuralgia, gabapentin therapy may be initiated as a single 300 mg dose on day 1,600 mg/day on day 2 (divided... 

Pharmacokinetics Gabapentin bioavailability is not dose-proportional. It circulates largely unbound (less than 3%) to plasma protein and is eliminated from the systemic circulation by renal excretion as unchanged drug it is not appreciably metabolized. 

Gabapentin Unclear 5-7 1-2 days Slow escalation of dose reduces the risk of adverse reactions. Renal elimination - observe possible need for dose reduction in elderly. Evidence of effect in zoster pain and in neuropathic pain. Not first choice... 

Gabapentin acts by increasing GABA activity, although its exact mechanism of action is unclear. It causes dose-related sedation and dizziness. It has been shown in randomised controlled trials to be effective in social anxiety disorder (Pande et al. 1999) and to benefit some patients with panic disorder (Pande et al. 2000). Pregabalin is a related compovmd that has recently demonstrated efficacy in GAD in a phase III study (Pande et al. 2003). 

The safety and efficacy of gabapentin as adjunctive therapy to CBZ and/or phenytoin has been assessed in adults, adolescents (Bruni, 1998), and children (Khur-ana et ah, 1996) with partial seizures. A decrease of 50% or more in frequency of complex partial -I- secondary generalized seizures was reported in 71% of patients on a mean maintenance dose of gabapentin of 1600 mg/day (Bruni, 1998). It has also been used in the treatment of spasticity in adolescents with multiple sclerosis (Cutter et al., 2000) and in adults and adolescents with neuropathic pain (Rosenberg et al.,... 

Gabapentin Decreases excitatory transmission by acting on VG Ca2+ channels presynaptically(a25 subunit) Bioavailability 50%, decreasing with increasing doses not bound to plasma proteins not metabolized ti/2 6—8 h Generalized tonic-clonic seizures, partial seizures, generalized seizures Toxicity Somnolence, dizziness, ataxia Interactions Minimal... 

Topiramate, another antiepileptic drug, may also be helpful in a dose of 400 mg daily, built up gradually. Small quantities of alcohol may suppress essential tremor but only for a short time. Alprazolam (in doses up to 3 mg daily) or gabapentin (100-2400 mg/d) is helpful in some patients. Others are helped by intramuscular injections of botulinum toxin. Thalamic stimulation by an implanted electrode and stimulator is often worthwhile in advanced cases refractory to pharmacotherapy. Diazepam, chlordiazepoxide, mephenesin, and antiparkinsonism agents have been advocated in the past but are generally worthless. Anecdotal reports of benefit from mirtazapine were not confirmed in a double-blind study, which found no effect on the tremor in most patients. 

A 28-year-old woman with bipolar depression developed clinical and biochemical evidence of hyperthyroidism, ascribed to thyroiditis, while taking gabapentin (4800 mg/day) in a clinical trial (429). The condition cleared after withdrawal, and subsequent exposure to a lower dose of gabapentin (1500 mg/day) was uneventful. 

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