Pirabene

Uses

Cerebral vascular accidents and cerebral insufficiencies: Ischaemic or even haemorrhagic acute accidents, chronic manifestations of the above accidents or of cerebral atherosclerosis.

Mental retardation in children: Ease of resuming individual contact, sociability and learning, improved intellectual performances and school results.

Behaviour and psychotic problems in old age: Memory deficits, particularly with regard to fixation and evocation asthenia adaption disorders, disturbed psychomotor reactions. Patients suffering from myoclonus of cortical origin.

Pirabene is also used to associated treatment for these conditions: Alcohol Dependency, Alcohol Withdrawl, Cognitive Deficits caused by Injuries, Craniocerebral, Cognitive Dysfunctions, Cognitive Impairments, Comatose caused by Blood Vessel (Vascular) Dysfunction, Comatose caused by CNS Toxicity, Comatose caused by Traumas, Learning Disorders, Myoclonus, Sickle Cell Disease (SCD), Giddiness caused by Injuries, Craniocerebral

How Pirabene works

Pirabene interacts with the polar heads in the phospholipids membrane and the resulting mobile drug-lipid complexes are thought to reorganize the lipids and influence membrane function and fluidity . Such interaction has been reported in a study that investigated the effects of neuronal outgrowth induced by beta amyloid peptides; while amyloid peptides cause lipid disorganization within the cell membranes leading to neuronal death, piracetam demonstrated to decrease the destabilizing effects of amyloid peptide . The authors suggest that piracetam induces a positive curvature of the membrane by occupying the polar groups in the phospholipids to counteract the negative curvature induced by amyloid peptides , which in turn would decrease the likelihood of membrane fusion . This mechanism of action is thought to improve membrane stability, allowing the membrane and transmembrane proteins to maintain and recover the three-dimensional structure or folding for normal function such as membrane transport, chemical secretion, and receptor binding and stimulation .

Through restored membrane fluidity, piracetam promotes restored neurotransmission such as glutamatergic and cholinergic systems, enhances neuroplasticity and mediates neuroprotective and anticonvulsant effects at the neuronal level . It is also demonstrated that piracetam also improves the fluidity of platelet membranes. At the vascular level, piracetam decreases adhesion of erythrocytes to cell wall and reduces vasospasm which in turn improves microcirculation including cerebral and renal blood flow .

Dosage

Pirabene dosage

Oral: Adults:

• In cerebro-cortical insufficiency disorders, usual dose is one tablet (800 mg) 3 times a day.
• In myoclonic seizures, a dose of 7.2 gm daily, increasing by 4.8 gm per day every 3 to 4 days up to maximum of 20 gm daily, given in 2 or 3 divided doses.

Oral: Children:

The daily dosage depends on the weight of the child, 50 mg/kg of body weight in 3 divided doses. Once the desired results has been obtained, reduce the initial dose by half.

Parenteral formulations: When parenteral administration is needed (e.g. swallowing difficulties, unconsciousness) Pirabene can be administered intravenously.When treating severe symptoms, 12 g daily may need to be administered as an intravenous infusion.

Pirabene is compatible (physico-chemical compatibility) with the perfusions of:

• Glucose 5%, 10%, 20%
• Fructose 5%, 10%, 20%
• Sodium chloride 0.9%
• Dextran 40 (10% in a 0.9% NaCl solution)
• Ringer Mannitol 20%
• HES solution (Hydroxy Ethyl Starch) 6% and 10%

The stability of these solutions has been demonstrated up to 24 hours.

Side Effects

The side effects reported include nervousness, agitation, irritability, anxiety and sleep disturbances. The incidence of these during clinical trials was (≤ 5%) and they were more often noted in the older patients taking > 2.4 gm daily. In the majority of cases, a dose reduction sufficed to make these symptoms disappear. Some patients may complain of fatigue or drowsiness, gastrointestinal problems, e.g. nausea, vomiting, diarrhoea and stomachache have also been reported but their incidence during clinical trials was ≤ 2%. Other symptoms e.g. vertigo, headache, trembling and sexual stimulation have occasionally been reported.

Toxicity

The cases of overdose with piracetam is rare. The highest reported overdose with piracetam was oral intake of 75g which was associated with diarrhea and abdominal pain; the signs were most likely related to the extreme high dose of sorbitol contained in the used formulation. In cases of acute, significant overdosage, stomach emptying by gastric lavage or induced emesis is recommended as there are no known antidotes for piracetam . Management for an overdose will most likely be symptomatic treatment and may include hemodialysis, where the extraction efficacy of the dialyser is 50 to 60% for the drug .

Oral LD50 in a mouse acute toxicity study was 2000 mg/kg .

Interaction

In a single case, confusion, irritability and sleep disorders were reported in concomitant use with thyroid extract. At present, no interaction has been observed with the following anti-epileptic drugs, clonazepam, carbamazepine, phenyton, phenobarbitone and sodium valporate, based on a small number of studies.

Volume of Distribution

Vd is approximately 0.6L/kg. Pirabene may cross the blood-brain barrier as it was measured in the cerebrospinal fluid following intravenous administration . Pirabene diffuses to all tissues except adipose tissues, crosses placental barrier and penetrates the membranes of isolated red blood cells .

Elimination Route

Pirabene displays a linear and time-dependent pharmacokinetic properties with low intersubject variability over a large range of doses. Pirabene is rapidly and extensively absorbed following oral administration with the peak plasma concentration is reached within 1 hour after dosing in fasted subjects. Following a single oral dose of 3.2 g piracetam, the peak plasma concentration (Cmax) was 84 µg/mL. Intake of food may decrease the Cmax by 17% and increase the time to reach Cmax (Tmax) from 1 to 1.5 hours. Tmax in the cerebrospinal fluid is achieved approximately 5 hours post-administration .

The absolute bioavailability of piracetam oral formulations is close to 100% and the steady state plasma concentrations are achieved within 3 days of dosing .

Half Life

The plasma half life of piracetam is approximately 5 hours following oral or intravenous administration. The half life in the cerebrospinal fluid was 8.5 hours .

Clearance

The apparent total body clearance is 80-90 mL/min .

Elimination Route

Pirabene is predominantly excreted via renal elimination, where about 80-100% of the total dose is recovered in the urine. Approximately 90% of the dose of piracetam is excreted in the urine as unchanged drug .

Pregnancy & Breastfeeding use

Pirabene should not be prescribed during pregnancy or when breast feeding, except under exceptional circumstances. Pirabene is able to cross the placenta.

Contraindication

Pirabene is contra-indicated in patients with severe renal insufficiency (creatinine clearance < 20 ml/min) and hepatic impairment. As the principal route of elimination for Pirabene is via the kidney, special care must be taken when treating patients known to suffer from renal insufficiency. Monitoring of renal function is recommended in such cases. The increase in half-life is directly related to the decrease in renal function and creatinine clearance. This is also true for the older patient in whom creatinine clearance is dependent on age. When the creatinine clearance is < 60 ml/min, or serum creatinine is >1.25 mg/100 ml, the dosage prescribed should be calculated as following:

CrCl 60-40 ml/min: Dosage should be 1/2 of normal dose

CrCl 40-20 ml/min: Dosage should be 1/4 of normal dose

Special Warning

Children: No formal pharmacokinetic study has been conducted in children.

Elderly: In the elderly, the half-life of piracetam is increased and the increase is related to the decrease in renal function in this population (see Section Dosage and Administration).

Renal impairment: Pirabene clearance is correlated to creatinine clearance. It is therefore recommended to adjust the daily dose of piracetam based on creatinine clearance in patients with renal impairment

Hepatic impairment: The influence of hepatic impairment on the pharmacokinetics of piracetam has not been evaluated. Because 80 to 100% of the dose is excreted in the urine as unchanged drug, hepatic impairment solely would not be expected to have a significant effect on piracetam elimination.

Acute Overdose

Pirabene appears to be devoid of toxicity even at very high doses and, therefore, the need for specific measures to be taken in case of an overdose is avoided. Drug Interactions: In a single case, confusion, irritability and sleep disorders were reported in concomitant use with thyroid extract. At present, no interaction has been observed with the following anti-epileptic drugs, clonazepam, carbamazepine, phenytoin, phenobarbitone and sodium valproate, based on a small number of studies.

Storage Condition

Store in a cool and dry place at a temperature below 30˚C , Keep away from sunlight. Keep out of the reach of children.

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