Drugs in Health and Disease 1: Antipsychotics Flashcards
Describe chlorpromazine
- Group of drugs it belongs to
- Indication
- Side effects
- State 2 other drugs in class
- Phenothiazine
- Used to treat psychosis, anti-emetic; strong sedative
- Moderate extapyramidal side effects
- Promazine, levomepromazine, perphenazine, fluphenazine
How do agonist work?
- Lock and key hypothesis: drug fits within receptor forming drug-receptor complex
Describe the dose response curve for agonist
How does the presence of a competitive anatagonist work?
- Log linear dose response curve
- Causes a parallel shift, there is no change in max response
- Greater shift with increased concentration of antagonist
- In the presence of naloxone, you need a greater amount of opioid for same “hit’
How does non-competitive inhibition effect the dose-response curve
- Causes the maximum response to decrease
- As the concentration of the antagonist increases, the maximum response decreases further
How does chlorpromazine exert its effects in the brain?
Describe its chemical properties and MOA
- Contains benzene rings that make it lipid soluble and able to pass BBB
- Antipsychotic effects by blocking postsynaptic dopamine receptors in limbic and cortical areas
- Same MOA to exert antiemetic activity but in the chemical trigger zone
- Side effects are directly related to dopamine blockade
Why might a patient on choropromazine present as if they are drunk?
- Side effects can make one appear so
- Strong sedation effects
- In combination with alcohol can be confusing presentation
What are antipsychotics used for generally speaking?
- In the short term they are used to calm disturbed patients despite underlying psychopathology
- Prevent harm to self and other
- Anxiolytic (should only be used in short term)
What are the physical characteristic features of choropromazine?
- White crystalline powder
- Soluble in water and alcohol
- Bitter taste
- Decomposes on exposure to air and light
- Melts at 196 degrees
Consider use of antipsychotics
How does dosing vary with route of administeration?
How should it be reviewed?
- IM doses should be less than PO doses as there is no first pass hepatic metabolism
- IM doses should also reflect activity level of patients, those who are active will have high blood flow to area which will increase the absorption rate
- Prescriptions should clearly. state dose for each route
- If antipsychotic used in emergency it should be reviewed daily
Which conditions might require use of neuroleptics?
- Schizophrenia
- Brain damage
- Mania
- Toxin derlirium
- Agitated depression
- Bipolar
Why are neuroleptics used in schizophrenia?
Alleviate the positive psychotic symptoms
- thought disorder
- hallucinations
- delusions
Prevent relapse
Poor at treating negative symptoms
How are neuroleptics used in long term for schizophrenic patients?
- Required to prevent relapses
- Doses effective in acute episodes should be continued prophylaxis
State the four dopaminergic pathways
- Mesolimbic- pleasure and reward
- Mesocortical- cognition, working memory and decision making
- Nigrostriatial- purposeful movement
- Tuberinfundibular- dopamine inhibits prolactin release
Why do first generation anti-psychotics have an extensive side effect profile?
- Not selective for any of the 4 dopamine pathways –> side effect
- Extrapyramidal symptoms and hyperprolactinaemia
Describe the side effect profile of the group 1 phenothiazines. Give an example
Group 1
- pronounced sedative effects
- moderate antimuscarinic effects (caused by blockade of cholinergic receptors)
- EP side effects
- Chlorpromazine, levomepromazine, promazine
