Nervepen

Uses

Baclofen is used for:

• Spasm.
• Spinal cord diseases.
• Cerebrovascular accidents or neoplastic or degenerative brain disease.
• Muscle spasm of cerebral origin especially infantile cerebral palsy.
• The alleviation of spasticity resulting from multiple sclerosis

Gabapentin is used for-

• Epilepsy
• Neuropathic pain (e.g. postherpetic neuralgia) and other pain conditions
• Bipolar disorder
• Headache syndrome
• Spasticity in multiple sclerosis and spinal cord diseases

Others indication are:

• Alcohol withdrawal
• Schizoaffective disorder
• Post-traumatic stress disorder
• Agitation and behavioural disturbances
• associated with dementia
• Lesch-Nyhan syndrome
• Essential tremor
• Restless legs syndrome
• Brachioradial pruritus
• Hemichorea/hemiballismus
• Hot Flashes

Nervepen is also used to associated treatment for these conditions: Joint Pain, Soreness, Muscle, Flexor spasm, Reversible Spasticity, Severe cerebral origin Spasticity, Severe spinal cord origin SpasticityPartial-Onset Seizures, Peripheral Neuropathic Pain, Postherpetic Neuralgia

How Nervepen works

The exact mechanism of action of baclofen is not fully understood at this time , . Many studies indicate that baclofen is a GABA-B receptor agonist , , , , . Despite this, there is no conclusive evidence that the effects of baclofen on GABA systems are involved in the production of its clinical effects .

Baclofen is an effective and widely used antispastic agent with a spinal site of action. Its mechanism of action and pharmacological properties are different from the effects of other antispastic agents. In addition, baclofen has central sites of action, shown by its adverse event profile and general CNS depressant properties . GABA-B receptors interact with signal transduction pathways and neurotransmitter systems. Baclofen exerts an antinociceptive effect. The clinical significance of this warrants further research data for clarification.

Baclofen depresses monosynaptic and polysynaptic reflex transmission, by various actions, and possibly including the stimulation of GABAβ-receptors. This stimulation results in the inhibition of excitatory neurotransmitter (glutamate and aspartate) release, which may normally contribute to pain and spasticity. Although baclofen is an analog of the inhibitory neurotransmitter gamma-amino-butyric acid (GABA), there are no conclusive data indicating GABA systems are involved in its clinical effects .

The precise mechanism through which gabapentin exerts its therapeutic effects is unclear. The primary mode of action appears to be at the auxillary α2δ-1 subunit of voltage-gated calcium channels (though a low affinity for the α2δ-2 subunit has also been reported). The major function of these subunits is to facilitate the movement of pore-forming α1 subunits of calcium channels from the endoplasmic reticulum to the cell membrane of pre-synaptic neurons. There is evidence that chronic pain states can cause an increase in the expression of α2δ subunits and that these changes correlate with hyperalgesia. Gabapentin appears to inhibit the action of α2δ-1 subunits, thus decreasing the density of pre-synaptic voltage-gated calcium channels and subsequent release of excitatory neurotransmitters. It is likely that this inhibition is also responsible for the anti-epileptic action of gabapentin.

There is some evidence that gabapentin also acts on adenosine receptors and voltage-gated potassium channels, though the clinical relevance of its action at these sites is unclear.

Dosage

Nervepen dosage

Adults:

Treatment should be started with low dose and increased gradually until optimum effect is achieved. The following dosage titration schedule is suggested:

5 mg 3 times daily for 3 days,

10 mg 3 times daily for 3 days,

15 mg 3 times daily for 3 days,

20 mg 3 times daily for 3 days,

25 mg 3 times daily for 3 days.

Thereafter, additional increases may be necessary. The optimum dosage generally ranges from 30 - 80 mg daily in 3 - 4 divided doses. Daily doses of 100 - 120 mg may be given to carefully supervised patients in hospitals.

Children:

Treatment should be started at a very low dose, e.g., 0.3 mg/kg per day in divided (preferably 4) doses. The dosage should be raised cautiously at 1-2 week intervals until it is sufficient for the child\'s individual needs. The usual dosage range for maintenance therapy is 0.75 to 2 mg/kg body weight per day. In children aged over 10 years a maximum daily dose of 2.5 mg/kg body weight may be given.

Renal Insufficiency:

Baclofen is excreted principally in urine as unchanged drug. So it may be necessary to reduce the dosage in patients with impaired renal function.

Neuropathic pain: 300 mg on day-1, then 300 mg twice on day-2, then 300 mg thrice on day-3, then increase the dose according to response in steps of 300 mg daily to maximum 1800 mg daily in three divided doses.

Partial seizure/epilepsy: 300 mg on day-1, then 300 mg twice on day-2, then 300 mg thrice on day-3, then increase the dose according to response in steps of 300 mg daily to maximum 2400 mg daily in three divided doses.

In case of children:

• For 3-12 years: 10 to 15 mg/kg, Incase of titration 25-35 mg/kg daily in 3 divided doses.
• Maintenance dose is 900 mg daily (body weight 26-36 Kg) or 1.2 gm daily (body weight 37-50 Kg).

Gabapentin can be taken orally with or without food.

Side Effects

The most common side effects include drowsiness, nausea, dizziness, lassitude, lightheadedness, confusion, fatigue, muscular pain & weakness and hypotension.

Generally Gabapentin is well tolerated but a few side effects like fatigue, dizziness , ataxia, weight gain, peripheral edema, dry mouth and somnolence, may occur. Rarely it may cause fulminate hepatic failure, or aplasticanemia.

Toxicity

LD50 after oral administration in rats: 145 mg/kg

Overdosage: Vomiting, muscular hypotonia, drowsiness, accommodation disorders, coma, respiratory depression, and seizures may occur with overdosage .

Pregnancy: This drug is a pregnancy category C drug. There are no adequate and well-controlled studies that have been performed with pregnant women. Baclofen should be used during pregnancy only if the potential benefit justifies the potential risk to the fetus .

Excretion in breastmilk: It is unknown whether this drug is excreted in human breast milk. Because many drugs are excreted in human milk, caution is warranted when baclofen is administered to a nursing woman .

The oral TDLo of gabapentin in humans is 2.86 mg/kg and the LD₅₀ in rats has been found to be >8000 mg/kg. Symptoms of overdose are consistent with the drug's adverse effect profile and involve CNS depression (e.g. dizziness, drowsiness, slurred speech, lethargy, loss of consciousness) and gastrointestinal symptoms such as diarrhea. Management of overdose should involve symptomatic and supportive treatment. Gabapentin can be removed by hemodialysis - this may be of benefit in some patients, such as those with impaired renal function.

Multi-drug overdoses involving gabapentin, particularly in combination with other CNS depressants such as opioids, can result in coma and death - this possibility should be considered when managing overdosage.

Precaution

Patients suffering from psychotic disorders, schizophrenia, depressive or manic disorders, confusional states or Parkinson\'s disease, should be treated cautiously with Baclofen. Baclofen stimulates gastric acid secretion and should be used with caution in patients with a history of peptic ulcer and avoided in those with active peptic ulcer disease . Liver function should be monitored in patients with liver disease; patients with renal impairment need a reduced dose. Baclofen should be used with caution in patients with respiratory impairment. Observations of increased blood sugar concentrations suggest caution in patients with diabetes mellitus. Care is also required in the elderly, in whom adverse effects may be more common, and in patients with cerebrovascular disease (who tolerate Baclofen poorly). Baclofen may cause drowsiness; patients affected should not drive or operate machinery. Abrupt withdrawal of Baclofen may result in a withdrawal syndrome and exacerbation of spasticity; dosage should be reduced gradually over at least 1 to 2 weeks, or longer if symptoms occur.

Patients should be instructed to take Gabapentin only as prescribed. While using Gabapentin patients should be instructed either not to drive a car or to operate other complex machinery until they have gained sufficient experiences about Gabapentin whether or not it affects their mental and/or motor performance adversely.

Interaction

Alcohol and other CNS depressants may exacerbate the CNS effects of Baclofen and should be avoided. There may be increased weakness if Baclofen is given to patients taking a tricyclic antidepressant and an increased hypotensive effect if it is given to patients receiving antihypertensive therapy.

Antacids may reduce the bioavailability of Gabapentin by up to 20%. Cimetidine may alter its reanal excretion. Gabapentin does not interact with other anti-epileptic drug or with oral contraceptive preparations.

Volume of Distribution

Apparent volume of distribution: 59 liters .

Baclofen does not readily cross the blood-brain barrier .

The apparent volume of distribution of gabapentin after IV administration is 58±6 L. The drug is found in the CSF in concentrations approximately 9-20% of the corresponding plasma concentrations and is secreted into breast milk in concentrations similar to that seen in plasma.

Elimination Route

Rapidly and almost completely absorbed from the gastrointestinal tract. Absorption may be dose-dependent, being reduced with increased doses .

Baclofen, when introduced directly into the intrathecal space, allows for effective CSF concentrations to be achieved with resulting plasma concentrations 100 times less than concentrations occurring with oral administration , .

Absorption of gabapentin is thought to occur solely via facilitated transport by the LAT1 transporter within the intestines. As this process is saturable, the oral bioavailability of gabapentin is inversely proportional to the administered dose - the oral bioavailability of a 900mg/day regimen is approximately 60%, whereas a 4800mg/day regimen results in only 27% bioavailability. The T_max of gabapentin has been estimated to be 2-3 hours. Food has no appreciable effect on gabapentin absorption.

Half Life

Elimination half-life: Approximately 5.5 hours .

The elimination t_1/2 of gabapentin in patients with normal renal function is 5-7 hours. In patients with reduced renal function, the elimination t_1/2 may be prolonged - in patients with a creatinine clearance of 16,17

Clearance

Total systemic clearance: 180 mL/min Renal clearance: 103 mL/min

Baclofen is primarily excreted unchanged by the kidneys. It should be administered cautiously, and it may be necessary to reduce the dosage in patients with reduced renal function .

Both the plasma clearance and renal clearance of gabapentin are directly proportional to the patient's creatinine clearance due to its primarily renal elimination.

Elimination Route

Baclofen is rapidly and extensively eliminated from the body. There is significant intersubject variation in elimination rates. Baclofen is excreted mainly by the kidney as unchanged drug. Seventy to eighty (70 - 80%) of a dose is measured in the urine as unchanged drug. The remainder of the dose is excreted as unchanged drug in the feces or as metabolites in the urine and feces. Excretion is complete within 72 hours after administration .

Gabapentin is eliminated solely in the urine as unchanged drug. Cimetidine, an inhibitor of renal tubular secretion, reduces clearance by approximately 12%, suggesting that some degree of tubular secretion is involved in the renal elimination of gabapentin.

Pregnancy & Breastfeeding use

There are no adequate and well controlled studies of Baclofen in pregnant women. So it should be used during pregnancy only if the potential benefit outweighs the potential risk to the fetus.

Baclofen is excreted in breast milk. However, evidence suggests that the quantities are so small that no undesirable effect on the infant would be expected.

Pregnancy: Gabapentin is a pregnancy category C drug; it should be used during pregnancy only if the potential benefit justifies the potential risk to the fetus.

Lactation: Gabapentin may be secreted through the breast milk like many other drugs , so it should be used in women who are nursing, only if the benefits clearly outweigh the risks.

Contraindication

Baclofen is contraindicated in patients with hypersensitivity to any component of this product.

Gabapentin is contraindicated in patients who have known hypersensitivity to the drug.

Special Warning

Renal Insufficiency: Baclofen is excreted principally in urine as unchanged drug. So it may be necessary to reduce the dosage in patients with impaired renal function.

Use in Children: Safety and effectiveness of Gabapentin in the management of neuropathic pain in pediatric patients have not been established. Safety and effectiveness of Gabapentin in the management of seizures in pediatric patients below the age of 3 years have not been established.

Renal impaired patient: In case of renal impaired patient Gabapentin doses must be reduced :

• CrCl >60 ml/min: 1200 mg/daily in 3 divided doses
• CrCl 30-60 ml/min: 600 mg/daily in 2 divided doses
• CrCl 15-30 ml/min: 300 mg/daily single dose
• CrCl <15 ml/min: 150 mg/daily single dose or 300 mg/every alternate day
• Heamodialysis: maximum 300 mg after each dialysis Gabapentin can be taken orally with or without food.

Acute Overdose

Prominent features are signs of central nervous system depression. No specific antidote of Baclofen is known. Elimination of the agent from GI tract, artificial respiration, administration of fluid with a diuretic and dialysis should be considered.

Storage Condition

Store in cool & dry place, away from children.

Tablets should be stored below 25° C and protected from light & moisture

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