Gabapentin effect

Cutter, N.C., Scott, D.D., Johnson, J.C., and Whiteneck, G. (2000) Gabapentin effect on spasticity in multiple sclerosis a placebo-controlled, randomized trial. Arch Phys Med Rehabil 81 164-169. 

Drugs with unknown mechanism of action are gabapentin, bromides (but see above effects on GABAergic transmission) and adrenocorticotropic hormone (ACTH), which is used in infantile spasms. 

Figure 16.7 The structure of some established antiepileptic drugs (AEDs) and some newer ones. Note that while the structures of phenytoin and ethosuximide are similar and also close to that of phenobarbitone, they are effective in different forms of epilepsy. Vigabatrin, progabide and gabapentin are clearly related to GABA. Muscimol is a GABAa agonist but is not an effective antiepileptic drug...

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. 

A number of non-hormonal therapies have been studied for symptomatic management of vasomotor symptoms, including antidepressants [e.g., selective serotonin reuptake inhibitors (SSRIs) and venlafaxine], herbal products (e.g., soy, black cohosh, and dong quai), and a group of miscellaneous agents (e.g., gabapentin, clonidine, and megestrol). The choice of therapy depends on the patient s concomitant disease states, such as depression and hypertension, and the risk for potential adverse effects. 

Overall, non-hormonal therapies are less effective in treating vasomotor symptoms than HRT but do offer an important option for women experiencing menopausal symptoms who cannot or are unwilling to take HRT. The antidepressants gabapentin and clonidine have the best evidence for efficacy of all the non-hormonal options and should be considered first as an alternative to HRT. The most important considerations in choosing an alternative therapy are the patient s comorbidities and the efficacy and safety of the medication. 

Anticonvulsants. Finally, several antiseizure medications have been tried. These include valproic acid (Depakote, Depakene), carbamazepine (Tegretol), Lamotrig-ine (Lamictal), and gabapentin (Neurontin). The anticonvulsants are effective treatments for bipolar disorder. Their use for major depression needs to be studied further. Please refer to Section 3.4 Bipolar Disorders. 

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. 

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. 

Recently, other medications have been evaluated as mood stabilizers. This includes gabapentin (Neurontin), lamotrigine (Lamictal), and topiramate (Topamax). Only lamotrigine has been shown in controlled trials to be effective in the treatment... 

In addition to treating insomnia, gabapentin has been used to treat epilepsy, anxiety disorders, and bipolar disorder. It is generally well tolerated with sedation and headaches being the only prominent side effects. Because gabapentin is excreted unchanged in urine, it does not require metabolism by the liver. It is therefore easily eliminated by elderly patients and those with liver disease, although it should be used with caution in those with poor renal (kidney) function. 

In recent years, some physicians have used gabapentin as an alternative treatment for mild but chronic agitation. There are no studies of its effectiveness, but gabapentin is easily tolerated and may be a reasonable alternative for some patients. 

---