Gabapentin (Neurontin®)

• Neurontin®

• Antiepileptic Agent

• Capsules 100 mg, 300 mg, and 400 mg
• Tablets 600 mg and 800 mg

• Treatment of neuropathic pain
• Treatment of Post Herpetic Neuralgia
• treatment of Insomnia
• treatment of anxiety

Mechanism of action:

• Gabapentin readily enters the brain and prevents seizures in a number of animal models of epilepsy.
• Gabapentin is structurally related to the neurotransmitter GABA (gammaaminobutyric acid), but does not possess affinity for either GABAA or GABAB receptor.
• Gabapentin binds with high affinity to the α2-δ (alpha-2-delta) subunit of voltage-gated calcium channels.
• Broad panel screening suggests it does not bind to other neurotransmitter receptors of the brain and does not interact with sodium channels

• Gabapentin is not metabolized to a significant extent in humans.
• Gabapentin does not induce or inhibit hepatic mixed function oxidase enzymes responsible for drug metabolism and does not interfere with the metabolism of commonly coadministered antiepileptic drugs.

Missed dose:

• If a dose is missed, the next one should be taken as soon as possible, however, if it is within 4 hours of the next dose, the missed dose is not to be taken and the patient should return to the regular dosing schedule.

Drugs that increase gabapentin level:

• Opioids and Naproxen

Drugs that decrease gabapentin level:

• Antacids

The most common adverse reactions observed are:

• somnolence
• ataxia
• fatigue
• nystagmus
• peripheral edema
• coordination abnormal
• depression
• myalgia
• hypertension
• anorexia
• flatulence
• gingivitis
• arthralgia
• vertigo
• hyperkinesia
• paresthesia
• decreased or absent reflexes, increased reflexes
• anxiety
• hostility
• alopecia
• eczema
• dry skin
• increased sweating
• abnormal vision
• Patients should be advised to refrain from activities requiring mental alertness or physical coordination until they are stabilized

Discontinuation of treatment:

• As with other anticonvulsant agents, abrupt withdrawal is not recommended because of the possibility of increased seizure frequency. There have been post-marketing reports of adverse events such as anxiety, insomnia, nausea, pain and sweating following abrupt discontinuation of treatment.

Concomitant use with opioids:

• Concomitant use of opioids with gabapentin has been associated with sedation, somnolence, loss of consciousness as well as serious and sometimes fatal cases of respiratory depression.
• Patients with low respiratory function, renal or hepatic impairment and the elderly are at higher risk of experiencing severe adverse effects associated with concomitant use.
• Gabapentin concentrations may increase in patients receiving concomitant opioids.

Suicidal Ideation:

• Suicidal ideation and behaviour have been reported in patients treated with antiepileptic agents in several indications. All patients treated with antiepileptic drugs, irrespective of indication, should be monitored for signs of suicidal ideation and behaviour and appropriate treatment should be considered.

Treatment of Overdosage:

• Gabapentin can be removed by hemodialysis