Gabritab At

Uses

Amitriptyline is used for depressive illness, particularly with anxiety and nocturnal enuresis in children.

Pregabalin is used for the management of neuropathic pain associated with diabetic peripheral neuropathy and management of post-herpetic neuralgia. It is also used for the adjunctive therapy for adult patients with partial onset seizures. It can be used for the management of fibromyalgia and neuropathic pain associated with spinal cord injury.

Gabritab At is also used to associated treatment for these conditions: Acute Depression, Anorexia Nervosa (AN), Attention Deficit Hyperactivity Disorder (ADHD), Bulimia Nervosa, Depression, Diabetic Neuropathies, Insomnia, Irritable Bowel Syndrome (IBS), Major Depressive Disorder (MDD), Migraine, Moderate Depression, Neuropathic Pain, Nocturnal Enuresis, Severe Depression, Sleep disorders and disturbances, Tension Headache, Moderate Agitation, Moderate Anxiety, Severe Anxiety, Severe agitationDiabetic Peripheral Neuropathic Pain (DPN), Epilepsies, Fibromyalgia, Generalized Anxiety Disorder (GAD), Neuropathic Pain, Partial-Onset Seizures, Peripheral Neuropathic Pain, Peripheral neuropathy, Postherpetic Neuralgia

How Gabritab At works

The mechanism of action of this drug is not fully elucidated. It is suggested that amitriptyline inhibits the membrane pump mechanism responsible for the re-uptake of transmitter amines, such as norepinephrine and serotonin, thereby increasing their concentration at the synaptic clefts of the brain , . These amines are important in regulating mood. The monoamine hypothesis in depression, one of the oldest hypotheses, postulates that deficiencies of serotonin (5-HT) and/or norepinephrine (NE) neurotransmission in the brain lead to depressive effects . This drug counteracts these mechanisms, and this may be the mechanism of amitriptyline in improving depressive symptoms.

Whether its analgesic effects are related to its mood-altering activities or attributable to a different, less obvious pharmacological action (or a combination of both) is unknown .

Although the mechanism of action has not been fully elucidated, studies involving structurally related drugs suggest that presynaptic binding of pregabalin to voltage-gated calcium channels is key to the antiseizure and antinociceptive effects observed in animal models.

By binding presynaptically to the alpha2-delta subunit of voltage-gated calcium channels in the central nervous system, pregabalin modulates the release of several excitatory neurotransmitters including glutamate, substance-P, norepinephrine, and calcitonin gene related peptide. In addition, pregabalin prevents the alpha2-delta subunit from being trafficked from the dorsal root ganglia to the spinal dorsal horn, which may also contribute to the mechanism of action.

Although pregabalin is a structural derivative of the inhibitory neurotransmitter gamma-aminobutyric acid (GABA), it does not bind directly to GABA or benzodiazepine receptors.

Dosage

Gabritab At dosage

Depression :

• Adults: Initially 50-70 mg a day in divided dose or as a single dose at night at bed time.
• Elderly and adolescents: 25-50 mg daily in divided doses or as single dose at bed time. Dose can be increased gradually as necessary to a maximum of 150-200 mg. Usual maintenance dose is 50-100 mg daily.

Nocturnal enuresis:

• 6-10 years: 10-20 mg at bed time.
• 11-16 years: 25-50 mg at bed time for up to 3 months and gradually withdrawn.

Neuropathic pain associated with diabetic peripheral neuropathy: The maximum recommended dose of Pregabalin is 100 mg three times a day (300 mg/day) in patients with creatinine clearance of at least 60 mL/min. Dosing should begin at 50 mg three times a day (150 mg/day) and may be increased to 300 mg/day within 1 week based on efficacy and tolerability.

Post-herpetic neuralgia: The recommended dose of Pregabalin is 75 to 150 mg two times a day, or 50 to 100 mg three times a day (150 to 300 mg/day) in patients with creatinine clearance of at least 60 mL/min. Dosing should begin at 75 mg two times a day, or 50 mg three times a day (150 mg/day) and may be increased to 300 mg/day within 1 week based on efficacy and tolerability.

Adjunctive therapy for adult patients with partial onset seizures: Pregabalin at doses of 150 to 600 mg/day has been shown to be effective as adjunctive therapy in the treatment of partial onset seizures in adults. The total daily doseshould be divided and given either two or three times daily. In general, it is recommended that patients be started on a total daily dose no greater than 150 mg/day (75 mg two times a day, or 50 mg three times a day). Based on individual patient response and tolerability, the dose may be increased to a maximum dose of 600 mg/day.

Management of Fibromyalgia: The recommended dose of Pregabalin for fibromyalgia is 300 to 450 mg/day. Dosing should begin at 75 mg two times a day (150 mg/day) and may be increased to 150 mg two times a day (300 mg/day) within 1 week based on efficacy and tolerability. Patients who do not experience sufficient benefit with 300 mg/day may be further increased to 225 mg two times a day (450 mg/day).

Neuropathic pain associated with spinal cord injury: The recommended dose range is 150 to 600 mg/day. The recommended starting dose is 75 mg two times a day (150 mg/day). The dose may be increased to 150 mg two times a day (300 mg/day) within 1 week based on efficacy and tolerability.

.Patients who do not experience sufficient pain relief after treatment with 300 mg/day and who tolerate pregabalin may be treated with up to 300 mg two times a day. Neurolin® capsules can be taken without regards to meals.

Side Effects

• Cardiovascular reactions: Hypotension, syncope, postural hypotension, hypertension, tachycardia, palpitations, myocardial infarction, arrythmias, and heart block stroke.
• CNS and neuromuscular: Confusional states, disturbed concentration disorientation, delusions, and hallucinations.
• Anticholinergic: Dry mouth, blurred vision, mydriasis, increased intraoccular pressure, hyperplasia.
• Allergic: Skin rash, urticaria, and photosensitization.
• Haematological: Bone-marrow depression including agranulocytosis, leukopenia, eosinophilia, and thrombocytopenia.
• Gastrointestinal: Nausea, epigastric distress, vomiting anorexia, diarrhoea.
• Endocrine: Testicular swelling, gynaecomastia; breast enlargement, galactorrhoea.
• Other reaction: Dizziness, weakness, fatigue, headache, weight loss

The most common side effects include dizziness, somnolence, dry mouth, edema, blurred vision, weight gain, and abnormal thinking.

Toxicity

Toxicity Data: Oral TDLO (child): 4167 μg/kg; Oral TDLO (man): 714 μg/kg/1D (intermittent); Oral TDLO (woman): 10 mg/kg .

Ingestion of 750 mg or more by an adult may result in severe toxicity. The effects in overdose are further increased by simultaneous ingestion of alcohol and another psychotropic agent . Symptoms of overdose include abnormally low blood pressure, confusion, convulsions, dilated pupils and other eye problems, disturbed concentration, drowsiness, hallucinations, impaired heart function, rapid or irregular heartbeat, reduced body temperature, stupor, and unresponsiveness or coma, among others , .

Use in pregnancy

For amitriptyline, only limited clinical data are available regarding its use in pregnancy. Amitriptyline is not recommended during pregnancy unless clearly required and only after careful consideration of both risks and benefits .

Use in breastfeeding

Amitriptyline and its metabolites are excreted into breast milk (corresponding to 0.6 % - 1 % of the maternal dose). A risk to the suckling child must be considered. A decision should be made as to whether it is appropriate to discontinue breastfeeding or to discontinue/abstain from the therapy of this medicinal product, considering the benefit of breastfeeding for the child and the benefit of therapy for the woman.

Effects on fertility

Animal studies have shown reproductive toxicity. No data on the effects of amitriptyline on human fertility are available .

Mutagenesis and carcinogenesis

The genotoxic potential of amitriptyline has been investigated in various in vitro and in vivo studies. Although these investigations showed some contradictory results, a potential of amitriptyline to lead to chromosome abnormalities cannot be excluded. Long-term carcinogenicity studies have not been performed to this date .

In a systematic review that included 38 randomized controlled trials, there were 20 identified adverse effects that were significantly associated with pregabalin, most of which involve the central nervous system and cognition. The identified adverse effects include vertigo, dizziness, balance disorder, incoordination, ataxia, blurred vision, diplopia, amblyopia, somnolence, confusional state, tremor, disturbance in attention, abnormal thinking, asthenia, fatigue, euphoria, edema, peripheral edema, dry mouth, and constipation .

The most common symptoms of pregabalin toxicity (dose range includes 800 mg/day and single doses up to 11,500 mg) include somnolence, confusion, restlessness, agitation, depression, affective disorder and seizures.

Since there is no antidote for pregabalin overdose, patients should receive general supportive care. If appropriate, gastric lavage or emesis may help eliminate unabsorbed pregabalin (healthcare providers should take standard precautions to maintain the airway).

Pregabalin pharmacokinetic properties suggest that extra-corporeal elimination methods including haemodialysis, may be useful in situations of severe toxicity. However, there are cases where patients have presented with very high serum levels of pregabalin and have been successfully managed with supportive care alone.

Precaution

Schizophrenic patients may develop increased symptoms of psychosis; patients with paranoid symptomatology may have an exaggeration of such symptoms. Depressed patients, particularly those with known manic-depressive illness, may experience a shift to mania or hypomania. In these circumstances the dose of Amitriptyline may be reduced or a major tranquilizer such as perphenazine may be administered concurrently.

The possibility of suicide in depressed patients remains until significant remission occurs. Potentially suicidal patients should not have access to large quantities of this drug. Prescriptions should be written for the smallest amount feasible.

Concurrent administration of Amitriptyline hydrochloride and electroshock therapy may increase the hazards associated with such therapy. Such treatment should be limited to patients for whom it is essential.

When possible, the drug should be discontinued several days before elective surgery. Both elevation and lowering of blood sugar levels have been reported. Amitriptyline hydrochloride should be used with caution in patients with impaired liver function.

Discontinuation of Pregabalin without tapering may produce insomnia, nausea, headache and diarrhea. So it should be tapered gradually over a minimum of 1 week rather than discontinued abruptly. Creatinine kinase may be elevated if treated with Pregabalin. It should be discontinued rapidly if myopathy is diagnosed or suspected or if creatinine kinase is elevated markedly.

Interaction

Monoamine oxidase inhibitors can potentiate the effects of Amitriptyline.

Anticholinergic agents: Amitriptylin should not be given with symptomatic agents such as adrenaline, epinephrine, isoprenaline, noradrenaline.

CNS depressant: Amitriptyline may enhance the response to alcohol, barbiturates.

Cemitidine: Cemitidine is reported to reduce hepatic metabolism of certain tricyclic antidepressants.

Volume of Distribution

The apparent volume of distribution (Vd)β estimated after intravenous administration is 1221 L±280 L; range 769-1702 L (16±3 L/kg) . It is found widely distributed throughout the body . Amitriptyline and the main metabolite nortriptyline pass across the placental barrier and small amounts are present in breast milk .

After oral administration of pregabalin, the reported apparent volume of distribution is roughly 0.5 L/kg.

Although pregabalin is not very lipophilic, it is able to cross the blood brain barrier(BBB). System L transporters facilitate the transport of large amino acids across the BBB and it has been confirmed that pregabalin is a substrate. This information suggests that system L transporters are responsible for pregabalin uptake into the BBB.

In rat models, pregabalin has been shown to cross the placenta.

Elimination Route

Rapidly absorbed following oral administration (bioavailability is 30-60% due to first pass metabolism). Peak plasma concentrations are reached 2-12 hours after oral or intramuscular administration . Steady-state plasma concentrations vary greatly and this variation may be due to genetic differences .

After oral dosing administered in the fasted state, pregabalin absorption is rapid, and extensive. Pregabalin oral bioavailability is reported to be ≥90% regardless of the dose. Cmax is attained within 1.5 hours after single or multiple doses, and steady state is attained within 24-48 hours with repeated administration. Both Cmax and AUC appear to be dose proportional.

Food decreases the rate of pregabalin absorption and as a result, lowers the Cmax by an estimated 25-30% and increases the Tmax to approximately 3 hours. However, the effect of food does not appear to impact the total absorption of pregabalin in a way that is clinically relevant. As a result, pregabalin can be administered with or without food.

Half Life

The elimination half-life (t1⁄2 β) amitriptyline after peroral administration is about 25 hours (24.65 ± 6.31 hours; range 16.49-40.36 hours) .

The elimination half life of pregabalin is 6.3 hours.

Clearance

The mean systemic clearance (Cls) is 39.24 ± 10.18 L/h (range: 24.53-53.73 L/h) . No clear effect of older age on the pharmacokinetics of amitriptyline has been determined, although it is possible that clearance may be decreased .

In young healthy subjects the mean renal clearance is estimated to be 67.0 to 80.9 mL mL/min. Given pregabalin's lack of plasma protein binding, this clearance rate suggests that renal tubular reabsorption is involved.

Elimination Route

Amitriptyline and its metabolites are mainly excreted in the urine. Virtually the entire dose is excreted as glucuronide or sulfate conjugate of metabolites, with approximately 2% of unchanged drug appearing in the urine . 25-50% of a single orally administered dose is excreted in urine as inactive metabolites within 24 hours . Small amounts are excreted in feces via biliary elimination .

Pregabalin is almost exclusively eliminated in the urine.

Further, based on preclinical studies, pregabalin does not appear to undergo racemization to the R enantiomer in the body.

Pregnancy & Breastfeeding use

Pregnancy Category C. Amitriptyline is not recommended during pregnancy, especially during the first and third trimester because the safety of Amitriptyline has not been established yet.

Amitriptyline is detectable in breast milk. Because of the serious adverse reactions in infants from Amitriptyline, a decision should be made whether to continue breast feeding or discontinue the drug

Pregnancy category C. So it should only used if potential benefit justifies the potential risks to the fetus.

Nursing mother: It is not known if pregabalin is excreted in human milk; it is, however, present in the milk of rats. So it should be used in nursing mother only if there is a clear benefit over the risk.

Contraindication

Amitriptyline is contraindicated in myocardial infarction; arrythmias, particularly heartblock of any degree; mania; severe liver disease. Initially sedation may effect the ability to drive or operate machinery. It should be used with caution in patients with a history of epilepsy, glaucoma, urinary retention, prostatic hypertrophy, constipation, cardiac disease, diabetes, pregnancy, hepatic impairment, thyroid disease, increased intraoccular pressure, psychoses (may aggravate mania).

Pregabalin is contraindicated in patients with known hypersensitivity to Pregabalin or any of its components.

Special Warning

Use in children & adolescents: The safety and effectiveness of Pregabalin have not been established in patients below the age of 18 years.

Use in elderly (Over 65 years of age): No dosage adjustment is necessary in elderly patients. Overdose: In overdoses up to 15 g, no unexpected adverse effects were reported.

Paediatric use: The safety and efficacy of pregabalin in paediatric patients have not been established.

Storage Condition

Keep containers well closed and stored below 25˚ C, protected from light.

Store at a cool & dry place, protected from light and moisture. Keep out of reach of the children.

Innovators Monograph

You find simplified version here Gabritab At