Mechanism and Side effects of Piracetam

Piracetam (2-oxo-l-pyrrolidine acetamide), the first noo- tropic agent, is a cyclic derivative of γ- aminobutyric acid (GABA), which can cross the BBB to concentrate selectively in the brain cortex. 

Mechanism of action

At low doses, piracetam increases both oxygen and glucose utilization via adenosine triphosphate (ATP) pathways and the release of some neurotransmit- ters - in particular dopamine metabolites - while at higher dosages, it is associated with platelet anti-aggregation and rheological efects with antithrombotic properties. 

It enhances the microcirculation by promoting erythrocyte deformability and reducing adherence to endo- thelial cells. However, studies of piracetam in acute stroke have been inconclusive, although improvement of aphasia in patients treated within 7 hours of stroke onset was seen. 

Related research

Several animal studies showed effects of piracetam on memory and facilitation of retention over 24 hours. A Cochrane review concluded that the usefulness of piracetam in patients with AD and VaD in small clinical trials is unclear, based mainly on subjective Global Impression of Change. 

These findings are supported by a larger Russian trial on 70 patients (37 women and 33 men, mean age 62 years), including 29 (41.5%) with PSD and 41 (58. 5%) with chronic cerebral ischaemia. Improvements in cognition (MMSE) and behaviour were better at a dose of 2400 mg/day. Piracetam was well tolerated. 

A review of 19 trials in patients with several forms of dementia and a protective effect in patients undergoing coronary artery bypass surgery appear to provide some support for a moderate effect of piracetam on cognitive impairment.

Side effects

Symptoms of general excitability, including anxiety, insomnia, irritability, headache, agitation, nervousness, tremor, and hyperkinesia, are occasionally reported.Other reported side effects include somnolence, weight gain, clinical depression, weakness, increased libido, and hypersexuality.

According to a 2005 review, piracetam has been observed to have the following side effects: hyperkinesia, weight gain, nervousness, somnolence, depression and asthenia.

Piracetam reduces platelet aggregation as well as fibrinogen concentration, and thus is contraindicated to patients suffering from cerebral hemorrhage.

Toxicity

The LD50 for oral consumption in humans has not been determined.The LD50 is 5.6 g/kg for rats and 20 g/kg for mice, indicating extremely low acute toxicity.For comparison, in rats the LD50 of vitamin C is 12 g/kg and the LD50 of table salt is 3 g/kg.