Atypical Antipsychotic - Pharmacokinetics

Pharmacokinetics

The most common route of administration of AAP is oral. Antipsychotics can also be injected, but this method is not as common. Once the antipsychotics are in the body they are lipid soluble and are readily absorbed from the digestive tract and can easily pass the blood brain barrier and placental barriers. Once in the brain the antipsychotics make their way to the synapse and work at the synapse by binding to the receptor (Culpepper, 2007). Antipsychotics are entirely destroyed by the body's metabolism and the metabolites are excreted in the urine (McKim, 2007). These drugs have relatively long half lives. Each drug has a different half life but the occupancy of the D2 receptor falls off within 24 hours with atypical antipsychotics, while lasting over 24 hours for the typical antipsychotics. This may explain why relapse into psychosis happens quicker with atypical antipsychotics than with typical antipsychotics, as the drug is excreted faster and is no longer working in the brain. Physical dependence with these drugs is very rare, therefore withdrawal symptoms are rarely seen. Sometimes if AAP are abruptly stopped psychotic symptoms, movement disorders and difficulty in sleep are seen. It is possible that withdrawal is rarely seen because the AAP are stored in the fat tissues in the body and slowly released.