Berlontin

Gabapentin.

Each 100 mg hard capsule contains 100 mg of gabapentin.
Each 300 mg hard capsule contains 300 mg of gabapentin.
Each 600 mg film-coated tablet contains 600 mg of gabapentin.
Excipients/Inactive ingredients: Berlontin 100 and 300 mg: Each capsule also contains corn starch and talc.
Capsule for Berlontin 100 mg: White-white No.3 (Gelatin and titanium dioxide).
Capsule for Berlontin 300 mg: Yellow size 1 (Gelatin and titanium dioxide).
Berlontin 600 mg: Each tablet also contains mannitol, hydroxypropylcellulose-L, poloxamer 407, magnesium stearate, and opadry II white (compose of polyvinyl alcohol, titanium dioxide, polyethylene glycol and talcum).

Pharmacotherapeutic groups: Other antiepileptics. ATC code: N03AX12.
Pharmacology: Pharmacodynamics: The precise mechanism of action of gabapentin is not known.
Gabapentin is structurally related to the neurotransmitter GABA (gamma-aminobutyric acid) but its mechanism of action is different from that of several other active substances that interact with GABA synapses including valproate, barbiturates, benzodiazepines, GABA transaminase inhibitors, GABA uptake inhibitors, GABA agonists, and GABA prodrugs. In vitro studies with radiolabeled gabapentin have characterized a novel peptide binding site in rat brain tissues including neocortex and hippocampus that may relate to anticonvulsant and analgesic activity of gabapentin and its structural derivatives. The binding site for gabapentin has been identified as the alpha2-delta subunit of voltage-gated calcium channels.
Gabapentin at relevant clinical concentrations does not bind to other common drug or neurotransmitter receptors of the brain including GABAA, GABAB, benzodiazepine, glutamate, glycine or N-methyl-D-aspartate receptors.
Gabapentin does not interact with sodium channels in vitro and so differs from phenytoin and carbamazepine. Gabapentin partially reduces responses to the glutamate agonist N-methyl-D-aspartate (NMDA) in some test systems in vitro, but only at concentrations greater than 100 μM, which are not achieved in vivo. Gabapentin slightly reduces the release of monoamine neurotransmitters in vitro. Gabapentin administration to rats increases GABA turnover in several brain regions in a manner similar to valproate sodium, although in different regions of brain. The relevance of these various actions of gabapentin to the anticonvulsant effects remains to be established. In animals, gabapentin readily enters the brain and prevents seizures from maximal electroshock, from chemical convulsants including inhibitors of GABA synthesis, and in genetic models of seizures.
A clinical trial of adjunctive treatment of partial seizures in paediatric subjects, ranging in age from 3 to 12 years, showed a numerical but not statistically significant difference in the 50% responder rate in favour of the gabapentin group compared to placebo. Additional post-hoc analyses of the responder rates by age did not reveal a statistically significant effect of age, either as a continuous or dichotomous variable (age groups 3-5 and 6-12 years). The data from this additional post-hoc analysis are summarised in the table as follows: See Table 1.

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Pharmacokinetics: Absorption: Following oral administration, peak plasma gabapentin concentrations are observed within 2 to 3 hours. Gabapentin bioavailability (fraction of dose absorbed) tends to decrease with increasing dose. Absolute bioavailability of a 300 mg capsule is approximately 60%. Food, including a high-fat diet, has no clinically significant effect on gabapentin pharmacokinetics.
Gabapentin pharmacokinetics are not affected by repeated administration. Although plasma gabapentin concentrations were generally between 2 μg/ml and 20 μg/ml in clinical studies, such concentrations were not predictive of safety or efficacy. Pharmacokinetic parameters are given in Table 2. (See Table 2.)

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Distribution: Gabapentin is not bound to plasma proteins and has a volume of distribution equal to 57.7 litres. In patients with epilepsy, gabapentin concentrations in cerebrospinal fluid (CSF) are approximately 20% of corresponding steady-state trough plasma concentrations. Gabapentin is present in the breast milk of breast-feeding women.
Metabolism: There is no evidence of gabapentin metabolism in humans. Gabapentin does not induce hepatic mixed function oxidase enzymes responsible for drug metabolism.
Elimination: Gabapentin is eliminated unchanged solely by renal excretion. The elimination half-life of gabapentin is independent of dose and averages 5 to 7 hours.
In elderly patients, and in patients with impaired renal function, gabapentin plasma clearance is reduced. Gabapentin elimination-rate constant, plasma clearance, and renal clearance are directly proportional to creatinine clearance.
Gabapentin is removed from plasma by haemodialysis. Dosage adjustment in patients with compromised renal function or undergoing haemodialysis is recommended (see Dosage & Administration).
Gabapentin pharmacokinetics in children were determined in 50 healthy subjects between the ages of 1 month and 12 years. In general, plasma gabapentin concentrations in children > 5 years of age are similar to those in adults when dosed on a mg/kg basis.
Linearity/Non-linearity: Gabapentin bioavailability (fraction of dose absorbed) decreases with increasing dose which imparts non-linearity to pharmacokinetic parameters which include the bioavailability parameter (F) e.g. Ae%, CL/F, Vd/F. Elimination pharmacokinetics (pharmacokinetic parameters which do not include F such as CLr and T_½), are best described by linear pharmacokinetics. Steady state plasma gabapentin concentrations are predictable from single-dose data.
Toxicology: Preclinical safety data: Carcinogenesis: Gabapentin was given in the diet to mice at 200, 600, and 2000 mg/kg/day and to rats at 250, 1000, and 2000 mg/kg/day for two years. A statistically significant increase in the incidence of pancreatic acinar cell tumors was found only in male rats at the highest dose. Peak plasma drug concentrations in rats at 2000 mg/kg/day are 10 times higher than plasma concentrations in humans given 3600 mg/day. The pancreatic acinar cell tumors in male rats are low-grade malignancies, did not affect survival, did not metastasize or invade surrounding tissue, and were similar to those seen in concurrent controls. The relevance of these pancreatic acinar cell tumors in male rats to carcinogenic risk in humans is unclear.
Mutagenesis: Gabapentin demonstrated no genotoxic potential. It was not mutagenic in vitro in standard assays using bacterial or mammalian cells. Gabapentin did not induce structural chromosome aberrations in mammalian cells in vitro or in vivo, and did not induce micronucleus formation in the bone marrow of hamsters.
Impairment of Fertility: No adverse effects on fertility or reproduction were observed in rats at doses up to 2000 mg/kg (approximately five times the maximum daily human dose on a mg/m2 of body surface area basis).
Teratogenesis: Gabapentin did not increase the incidence of malformations, compared to controls, in the offspring of mice, rats, or rabbits at doses up to 50, 30 and 25 times respectively, the daily human dose of 3600 mg, (four, five or eight times, respectively, the human daily dose on a mg/m² basis).
Gabapentin induced delayed ossification in the skull, vertebrae, forelimbs, and hindlimbs in rodents, indicative of fetal growth retardation. These effects occurred when pregnant mice received oral doses of 1000 or 3000 mg/kg/day during organogenesis and in rats given 500, 1000, or 2000 mg/kg prior to and during mating and throughout gestation. These doses are approximately 1 to 5 times the human dose of 3600 mg on a mg/m² basis.
No effects were observed in pregnant mice given 500 mg/kg/day (approximately ½ of the daily human dose on a mg/m² basis).
An increased incidence of hydroureter and/or hydronephrosis was observed in rats given 2000 mg/kg/day in a fertility and general reproduction study, 1500 mg/kg/day in a teratology study, and 500, 1000, and 2000 mg/kg/day in a perinatal and postnatal study. The significance of these findings is unknown, but they have been associated with delayed development. These doses are also approximately 1 to 5 times the human dose of 3600 mg on a mg/m² basis.
In a teratology study in rabbits, an increased incidence of post-implantation fetal loss, occurred in doses given 60, 300, and 1500 mg/kg/day during organogenesis. These doses are approximately ¼ to 8 times the daily human dose of 3600 mg on a mg/m² basis.

Epilepsy: Gabapentin is indicated as adjunctive therapy in the treatment of partial onset seizures with and without secondary generalization in adults and children aged 3 years and above (see Pharmacology: Pharmacodynamics under Actions).
Gabapentin is indicated as monotherapy in the treatment of partial seizures with and without secondary generalization in adults and adolescents aged 12 years and above.
Treatment of peripheral neuropathic pain: Gabapentin is indicated for the treatment of peripheral neuropathic pain such as painful diabetic neuropathy and post-herpetic neuralgia in adults.

For oral use.
Gabapentin can be given with or without food and should be swallowed whole with sufficient fluid intake (e.g. a glass of water).
For all indications a titration scheme for the initiation of therapy is described in Table 3, which is recommended for adults and adolescents aged 12 years and above. Dosing instructions for children under 12 years of age are provided under a separate sub-heading later in this section. (See Table 3.)

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Epilepsy: Epilepsy typically requires long-term therapy. Dosage is determined by the treating physician according to individual tolerance and efficacy. When in the judgment of the clinician there is a need for dose reduction, discontinuation, or substitution with an alternative medication, this should be done gradually over a minimum of one week.
Adults and adolescents: In clinical trials, the effective dosing range was 900 to 3600 mg/day. Therapy may be initiated by titrating the dose as described in Table 3 or by administering 300 mg three times a day (TID) on Day 1. Thereafter, based on individual patient response and tolerability, the dose can be further increased in 300 mg/day increments every 2-3 days up to a maximum dose of 3600 mg/day. Slower titration of gabapentin dosage may be appropriate for individual patients. The minimum time to reach a dose of 1800 mg/day is one week, to reach 2400 mg/day is a total of 2 weeks, and to reach 3600 mg/day is a total of 3 weeks. Dosages up to 4800 mg/day have been well tolerated in long-term open-label clinical studies. The total daily dose should be divided in three single doses, the maximum time interval between the doses should not exceed 12 hours to prevent breakthrough convulsions.
Children aged 3 years and above: The starting dose should range from 10 to 15 mg/kg/day, given in three divided doses, and the effective dose is reached by upward titration over a period of approximately three days. The recommended maintenance dose in children aged 3 to 4 years of age is 40 mg/kg/day, given in three divided doses. The recommended maintenance dose in patients 5 to 11 years of age is 25 mg/kg/day to 35 mg/kg/day, given in three divided doses. Dosages up to 50 mg/kg/day have been well tolerated in a long-term clinical study. The maximum time interval between doses should not exceed 12 hours.
It is not necessary to monitor gabapentin plasma concentrations to optimize gabapentin therapy. Further, gabapentin may be used in combination with other antiepileptic medicinal products without concern for alteration of the plasma concentrations of gabapentin or serum concentrations of other antiepileptic medicinal product.
Peripheral neuropathic pain: Adults: The therapy may be initiated by titrating the dose as described in Table 3. Alternatively, the starting dose is 900 mg/day given as three equally divided doses. Thereafter, based on individual patient response and tolerability, the dose can be further increased in 300 mg/day increments every 2-3 days up to a maximum dose of 3600 mg/day. Slower titration of gabapentin dosage may be appropriate for individual patients. The minimum time to reach a dose of 1800 mg/day is one week, to reach 2400 mg/day is a total of 2 weeks, and to reach 3600 mg/day is a total of 3 weeks.
In the treatment of peripheral neuropathic pain such as painful diabetic neuropathy and post-herpetic neuralgia, efficacy and safety have not been examined in clinical studies for treatment periods longer than 5 months. If a patient requires dosing longer than 5 months for the treatment of peripheral neuropathic pain, the treating physician should assess the patient's clinical status and determine the need for additional therapy.
Instruction for all areas of indication: In patients with poor general health, i.e., low body weight, after organ transplantation etc., the dose should be titrated more slowly, either by using smaller dosage strengths or longer intervals between dosage increases.
Use in elderly patients (over 65 years of age): Elderly patients may require dosage adjustment because of declining renal function with age (see Table 4). Somnolence, peripheral oedema and asthenia may be more frequent in elderly patients.
Use in patients with renal impairment: Dosage adjustment is recommended in patients with compromised renal function as described in Table 4 and/or those undergoing haemodialysis. Gabapentin 100 mg capsules can be used to follow dosing recommendations for patients with renal insufficiency. (See Table 4.)

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Use in patients undergoing haemodialysis: For anuric patients undergoing haemodialysis who have never received gabapentin, a loading dose of 300 to 400 mg, then 200 to 300 mg of gabapentin following each 4 hours of haemodialysis, is recommended. On dialysis-free days, there should be no treatment with gabapentin.
For renally impaired patients undergoing haemodialysis, the maintenance dose of gabapentin should be based on the dosing recommendations found in Table 4. In addition to the maintenance dose, an additional 200 to 300 mg dose following each 4-hour haemodialysis treatment is recommended.

Acute, life-threatening toxicity has not been observed with gabapentin overdoses of up to 49 g. Symptoms of the overdoses included dizziness, double vision, slurred speech, drowsiness, lethargy and mild diarrhoea. All patients recovered fully with supportive care. Reduced absorption of gabapentin at higher doses may limit drug absorption at the time of overdosing and, hence, minimize toxicity from overdoses.
Although gabapentin can be removed by haemodialysis, based on prior experience it is usually not required. However, in patients with severe renal impairment, haemodialysis may be indicated.
An oral lethal dose of gabapentin was not identified in mice and rats given doses as high as 8000 mg/kg. Signs of acute toxicity in animals included ataxia, laboured breathing, ptosis, hypoactivity, or excitation.

Hypersensitivity to the active substance or to any of the excipients.

If a patient develops acute pancreatitis under treatment with gabapentin, discontinuation of gabapentin should be considered (see Adverse Reactions).
Although there is no evidence of rebound seizures with gabapentin, abrupt withdrawal of anticonvulsants in epileptic patients may precipitate status epilepticus (see Dosage & Administration).
As with other antiepileptic medicinal products, some patients may experience an increase in seizure frequency or the onset of new types of seizures with gabapentin.
As with other anti-epileptics, attempts to withdraw concomitant anti-epileptics in treatment refractory patients on more than one anti-epileptic, in order to reach gabapentin monotherapy have a low success rate.
Gabapentin is not considered effective against primary generalized seizures such as absences and may aggravate these seizures in some patients. Therefore, gabapentin should be used with caution in patients with mixed seizures including absences.
The drug may cause hematologic disorder, for examples, leucopenia, and in rare cases, thrombocytopenia.
Use this drug with cautions in patients with liver or kidney disease (see Dosage & Administration and Adverse Reactions).
Laboratory tests: False positive readings may be obtained in the semi-quantitative determination of total urine protein by dipstick tests. It is therefore recommended to verify such a positive dipstick test result by methods based on a different analytical principle such as the Biuret method, turbidimetric or dye-binding methods, or to use these alternative methods from the beginning.
Patients with rare hereditary problems of galactose intolerance, the Lapp lactase deficiency or glucose-galactose malabsorption should not take this medicine.
Effects on ability to drive and use machines: Gabapentin may have minor or moderate influence on the ability to drive and use machines. Gabapentin acts on the central nervous system and may cause drowsiness, dizziness or other related symptoms. Even, if they were only of mild or moderate degree, these undesirable effects could be potentially dangerous in patients driving or operating machinery. This is especially true at the beginning of the treatment and after increase in dose.
Use in Children: The effects of long-term (greater than 36 weeks) gabapentin therapy on learning, intelligence, and development in children and adolescents have not been adequately studied. The benefits of prolonged therapy must therefore be weighed against the potential risks of such therapy.
Use in the Elderly: No systematic studies in patients 65 years or older have been conducted with gabapentin. In one double blind study in patients with neuropathic pain, somnolence, peripheral oedema and asthenia occurred in a somewhat higher percentage in patients aged 65 years or above, than in younger patients. Apart from these findings, clinical investigations in this age group do not indicate an adverse event profile different from that observed in younger patients.

Risk related to epilepsy and antiepileptic medicinal products in general: The risk of birth defects is increased by a factor of 2 - 3 in the offspring of mothers treated with an antiepileptic medicinal product. Most frequently reported are cleft lip, cardiovascular malformations and neural tube defects. Multiple antiepileptic drug therapy may be associated with a higher risk of congenital malformations than monotherapy, therefore it is important that monotherapy is practiced whenever possible. Specialist advice should be given to women who are likely to become pregnant or who are of childbearing potential and the need for antiepileptic treatment should be reviewed when a woman is planning to become pregnant. No sudden discontinuation of antiepileptic therapy should be undertaken as this may lead to breakthrough seizures, which could have serious consequences for both mother and child. Developmental delay in children of mothers with epilepsy has been observed rarely. It is not possible to differentiate if the developmental delay is caused by genetic, social factors, maternal epilepsy or the antiepileptic therapy.
Risk related to gabapentin: There are no adequate data from the use of gabapentin in pregnant women.
Studies in animals have shown reproductive toxicity (see Pharmacology: Toxicology: Preclinical safety data under Actions). The potential risk for humans is unknown. Gabapentin should not be used during pregnancy unless the potential benefit to the mother clearly outweighs the potential risk to the foetus.
No definite conclusion can be made as to whether gabapentin is associated with an increased risk of congenital malformations when taken during pregnancy, because of epilepsy itself and the presence of concomitant antiepileptic medicinal products during each reported pregnancy.
Gabapentin is excreted in human milk. Because the effect on the breast-fed infant is unknown, caution should be exercised when gabapentin is administered to a breast-feeding mother. Gabapentin should be used in breast-feeding mothers only if the benefits clearly outweigh the risks.

The adverse reactions observed during clinical studies conducted in epilepsy (adjunctive and monotherapy) and neuropathic pain have been provided in a single list as follows by class and frequency (very common (> 1/10), common (>1/100, <1/10), uncommon (>1/1000, <1/100) and rare (>1/10,000; <1/1,000). Where an adverse reaction was seen at different frequencies in clinical studies, it was assigned to the highest frequency reported.
Within each frequency grouping, undesirable effects are presented in order of decreasing seriousness.
Infections and infestations: Very Common: Viral infection.
Common: Pneumonia, respiratory infection, urinary tract infection, infection, otitis media.
Blood and the lymphatic system disorders: Common: leucopenia.
Rare: thrombocytopenia.
Immune system disorders: Rare: allergic reactions (e.g. urticaria).
Metabolism and Nutrition Disorders: Common: anorexia, increased appetite.
Psychiatric disorders: Common: hostility, confusion and emotional lability, depression, anxiety, nervousness, thinking abnormal.
Rare: hallucinations.
Nervous system disorders: Very Common: somnolence, dizziness, ataxia.
Common: convulsions, hyperkinesias, dysarthria, amnesia, tremor, insomnia, headache, sensations such as paresthesia, hypaesthesia, coordination abnormal, nystagmus, increased, decreased, or absent reflexes.
Rare: movement disorders (e.g. choreoathetosis, dyskinesia, dystonia).
Eye disorders: Common: visual disturbances such as amblyopia, diplopia.
Ear and Labyrinth disorders: Common: vertigo.
Rare: tinnitus.
Cardiac disorders: Rare: palpitations.
Vascular disorder: Common: hypertension, vasodilatation.
Respiratory, thoracic and mediastinal disorders: Common: dyspnoea, bronchitis, pharyngitis, cough, rhinitis.
Gastrointestinal disorders: Common: vomiting, nausea, dental abnormalities, gingivitis, diarrhea, abdominal pain, dyspepsia, constipation, dry mouth or throat, flatulence.
Rare: pancreatitis.
Hepatobiliary disorders: Rare: hepatitis, jaundice.
Skin and subcutaneous tissue disorders: Common: facial oedema, purpura most often described as bruises resulting from physical trauma, rash, pruritus, acne.
Rare: Stevens-Johnson syndrome, angioedema, erythema multiforme, alopecia.
Musculoskeletal, connective tissue and bone disorders: Common: arthralgia, myalgia, back pain, twitching.
Renal and urinary disorders: Common: incontinence.
Rare: acute renal failure.
Reproductive system and breast disorders: Common: impotence.
General disorders and administration site conditions: Very Common: fatigue, fever.
Common: peripheral or generalized oedema, abnormal gait, asthenia, pain, malaise, flu syndrome.
Rare: withdrawal reactions (mostly anxiety, insomnia, nausea, pains, sweating), chest pain.
Sudden unexplained deaths have been reported where a causal relationship to treatment with gabapentin has not been established.
Investigations: Common: WBC (white blood cell count) decreased, weight gain.
Rare: Blood glucose fluctuations in patients with diabetes, elevated liver function tests.
Injury and poisoning: Common: accidental injury, fracture, abrasion.
Under treatment with gabapentin cases of acute pancreatitis were reported. Causality with gabapentin is unclear (see Precautions).
Respiratory tract infections, otitis media, convulsions and bronchitis were reported only in clinical studies in children. Additionally, in clinical studies in children, aggressive behaviour and hyperkinesias were reported commonly.

In a study involving healthy volunteers (N=12), when a 60 mg controlled-release morphine capsule was administered 2 hours prior to a 600 mg gabapentin capsule, mean gabapentin AUC increased by 44% compared to gabapentin administered without morphine. Therefore, patients should be carefully observed for signs of CNS depression, such as somnolence, and the dose of gabapentin or morphine should be reduced appropriately.
No interaction between gabapentin and phenobarbital, phenytoin, valproic acid, or carbamazepine has been observed.
Gabapentin steady-state pharmacokinetics are similar for healthy subjects and patients with epilepsy receiving these antiepileptic agents.
Coadministration of gabapentin with oral contraceptives containing norethindrone and/or ethinyl estradiol, does not influence the steady-state pharmacokinetics of either component.
Coadministration of gabapentin with antacids containing aluminium and magnesium, reduces gabapentin bioavailability up to 24%. It is recommended that gabapentin be taken at the earliest two hours following antacid administration.
Renal excretion of gabapentin is unaltered by probenecid.
A slight decrease in renal excretion of gabapentin that is observed when it is coadministered with cimetidine is not expected to be of clinical importance.

Incompatibilities: Not applicable.
Special precautions for disposal: No special requirements.

Store below 30°C.
Shelf life: 2 years.

Anticonvulsants / Drugs for Neuropathic Pain

N02BF01 - gabapentin ; Belongs to the class of gabapentinoids. Used to relieve pain and other conditions.

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