Each capsule contains gabapentin 100 mg, 300 mg and 400 mg.
Pharmacology: Pharmacodynamics: Mechanism of Action: Gabapentin is structurally related to GABA. However, it does not bind to GABAA or GABAB receptors, and it does not appear to influence synthesis or uptake of GABA. The exact mechanism of action of gabapentin is unknown and remains to be established. High affinity gabapentin binding sites have been found to be located throughout the brain; these sites correspond to presence of voltage-gated calcium ion channels specifically possessing the alpha-2-delta-1 subunit. This channel appears to be located presynaptically, and may modulate the release of excitatory neurotransmitters which participate in epileptogenesis and nociception.
Pharmacokinetics: Absorption: Gabapentin is absorbed from the gastrointestinal tract by means of a saturable mechanism.
Gabapentin bioavailability is not dose-proportional. As the dose is increased, bioavailability decreases.
After multiple dosing peak plasma concentrations are usually achieved within 2 to 3 hours of a dose and steady state achieved within 1 to 2 days.
Distribution: Gabapentin is widely distributed throughout the body but binding to plasma proteins is minimal (<3%).
Gabapentin is actively transported and the placenta and distributed into breast milk.
Metabolism: Gabapentin is not appreciably metabolized.
Excretion: Most of a dose is excreted unchanged in the urine with the remainder appearing in the faces. The elimination half-life is 5 to 7 hours.
GABTIN is an antiepileptic used as monotherapy or adjunctive therapy in the treatment of partial seizures with or without secondary generalisation. Gabapentin is also used in the treatment of neuropathic pain.
The recommended dose:
Adult and children older than 12 years of age.
Usual dosage: 900-1800 mg/day given in a divided dosage (3 times a day).
Dosage Tritration: using 300 mg or 400 mg titrate dose up to 1,800 mg/day (3 divided doses daily).
Neuropathic pain: Initial dosage:
A single 300 mg dose on day 1,600 mg/day on day 2 (divided twice daily), and 900 mg/day on day 3 (divided 3 times daily).
The dose can subsequently be titrated up as needed for pain relief to a daily dose of 1,800 mg (divided 3 times daily).
In clinical studies, efficacy was demonstrated over a range of doses from 1,800 mg/day to 3,600 mg/day with comparable effects across the dose range. Additional benefit of using doses greater than 1,800 mg/day was not demonstrated.
Renal function impairment:
Dosage adjustment in patients with compromised renal function or undergoing hemodialysis recommended as follows: See Table 1.
Click on icon to see table/diagram/image
Over dosage of gabapentin is generally mild. The patients can be recovered by supportive care. The acute oral overdose symptom includes: drowsiness, dizziness, gastrointestinal disturbance, hypotension, and mild tachycardia. These effects developed in under 5 hours and lasted for less than 24 hours.
Treatment: Gabapentin can be removed by haemodialysis. Although haemodialysis has not been performed in the few overdose cases reported, it may be indicated by the patient's clinical state or in patients with significant renal impairment.
Contraindicated in patients with known hypersensitivity to gabapentin or its ingredient.
Gabapentin should be used with caution in patients with renal impairment and in those undergoing hemodialysis, elderly, diabetes mellitus, pregnancy, breast-feeding women.
Avoid abrupt withdrawal since it may cause anxiety, insomnia, nausea, pain, and sweating. The administration should be tapered off over at least 1 week.
False positive readings h ave been reported with some urinary protein tests in patients taking gabapentin.
Gabapentin may cause CNS depression, which may impair physical or mental abilities. Patients must be cautioned about performing tasks which require mental alertness. Avoid driving, operating potential dangerous machinery while taking gabapentin.
Antiepileptics are associated with an increased risk of suicidal behavior/thoughts with use (regardless of indication); patients should be monitored for signs/symptoms of depression, suicidal tendencies, and other unusual behavior changes during therapy and instructed to inform their healthcare provider immediately if symptoms occur.
Effects with other sedative drugs or ethanol may be potentiated.
Male rat studies demonstrated an association with pancreatic adenocarcinoma (clinical implication unknown).
Pediatric patients (3-12 years of age) have shown increased incidence of CNS related adverse effects, including emotional ability, hostility, thought disorder, and hyperkinesia.
Pregnancy category: C.
There are adequate and well-contorted studies in pregnant women. Use during pregnancy only if the potential benefit to the mother is out-weighs the potential risk to the fetus.
There is an increased risk of teratogenicity associated with the use of antiepileptic drugs. Women taking antiepileptic drugs who may become pregnant should be informed of the possible consequences. Those who wish to become pregnant should be referred to an appropriate specialist for advice. Women who become pregnant should be counselled and offered antenatal screening (alphafetoprotein measurement and a second trimester ultrasound scan).
Gabtin 300 is present in milk during lactation, although, it is acceptable in the normal dosage.
See Table 2.
Click on icon to see table/diagram/image
Antacids: The absorption of gabapentin from the gastrointestinal tract is reduced by antacids containing aluminium with magnesium. It is recommended that gabapentin is taken at least 2 hours after any such antacid.
Morphine: Patients receiving both drugs should be monitored for signs of CNS depression and doses should be reduced accordingly as morphine is reported to reduce the clearance of gabapentin.
Cimetidine: Cimetidine has also been reported to reduce the renal clearance of gabapentin. The decrease in gabapentin excretion is not expected to be of clinical importance.
Hydrocodone: Coadministration increases gabapentin AUC values by 14%. Coadministration decreases hydrocodone Cmax and AUC values in a dose dependent manner Cmax and AUC values were 3% and 4% lower, respectively after administration of 125 mg gabapentin and 27% to 22% lower, respectively after administration of 500 mg gabapentin.
The mechanism for this interaction and the magnitude of interaction at other doses is unknown.
Contraceptive, oral: The Cmax of norethindrone was 13% higher when coadministered with gabapentin; this interaction is not expected to be of clinical importance.
Naproxen: Coadministration (n=18) of naproxen sodium capsules (250 mg) with gabapentin (125 mg) appears to increase the amount of gabapentin absorbed by 12% to 15%. Gabapentin had no effect on naproxen pharmacokinetic parameters. These doses are lower than the therapeutic doses for both drugs. The magnitude of interaction within the recommended dose ranges of either drug is not known.
Other antiepileptic drugs: Gabapentin is not appreciably metabolized nor does it interfere with the metabolism of commonly coadministered antiepileptic drugs.
Lab test interactions: Because false positive readings were reported with the Ames N-Multistix SG dipstick test for urinary protein when gabapentin was added to other antiepileptic drugs, the more specific sulfosalicylic acid precipitation procedure is recommended to determine the presence of urine protein.
Store below 30°C, protect from light.
N03AX12 - gabapentin ; Belongs to the class of other antiepileptics.
Cap 100 mg (white hard printed with "GABTIN/100 mg" on one side and "ATC" in blue triangle) x 10 x 10's. 300 mg (yellow hard printed with "GABTIN/300 mg" on one side and "ATC" in blue triangle) x 10 x 10's. 400 mg (orange hard printed with "GABTIN/400 mg" on one side and "ATC" in blue triangle) x 10 x 10's.