29.1 General Principles Flashcards
What are some general classes of Psychotropic medications?
Antidepressants, Antipsychotics, Mood stabilizers, Anxiolytics, Hypnotics, Cognitive enhancers, stimulants.
What characteristics distinguish drugs within the same class? How does this relate to an individual patient’s response?
Drugs within the same class often have subtle differences in molecular structure, types of interactions with neurotransmitter systems, differences in pharmacokinetics, the presence or absence of active metabolites, and protein binding.
These differences in addition to the biochemistry of the patient account for efficacy, tolerability, safety.
Difference between pharmacokinetics and pharmacodynamics?
Kinetics: what the body does to a drug
Dynamics: what drug does to body
What are some major considerations included in Pharmacodynamics?
Receptor mechanisms, dose-response curve, therapeutic index, development of tolerance, dependence and withdrawal phenomena.
Other than altering synaptic concentrations of neurotransmitters, what are some other ways could a drug potentially produce an effect?
Anti-inflammatory effects such as the antidepressant effect produced by Minocycline.
Also, multiple obscure actions several steps removed (downstream effects) are probably responsible for a lot of the clinical effects.
What is an example of early-onset side effects that tend to rapidly diminish?
Nausea occurring with SSRI’s or venlafaxine. Sedation occurring with Mirtazapine.
What is an example of an early-onset but persistent side effect?
Dry mouth associated with noradrenergic reuptake inhibition or antimuscarinic activity.
What is an example of late-appearing side effects?
Weight gain in SSRI’s (after initial loss). Early activation or agitation may be followed by constant fatigue or apathy.
What are some examples of serious side effects from psychiatric medications?
Agranulocytosis (Clozapine), SJS (Lamictal), Hepatic Failure (Nefazodone), Stroke (Phenelzine), Heart Block (Thioridazine).
Which atypical antipsychotic medication can cause severe akathisia?
Abilify
What medications can cause hyponatremia?
Trileptal (Oxcarbazepine) and SSRI’s.
Define the Therapeutic Index.
The relative measure of the toxicity or safety of a drug and is defined as the ration of the median toxic dose (the dose at which 50% of the population has toxic effect) to the median effective dose (the dose at which 50% of the population has a positive effect.
Safer drugs = high TI
More dangerous drugs = low TI
Define Therapeutic Window.
The window between the minimum effective concentration (MEC) and the minimum toxic concentration (MTC).
Which groups of medications reduce renal clearance of Lithium?
ACE Inhibitors, NSAID’s and Thiazides.
What is the potency of a drug?
Relative dose required to achieve a certain dose
When a patient experiences repeated drug failures, what things should you consider upon reassessment?
- Was the original diagnosis correct? Consider medical conditions and/or recreational drugs.
- Are the observed symptoms actually a result of the treatment? For example, akathisia with antipsychotics or emotional blunting in long-term SSRI use.
- Was the drug administered at the appropriate dosage for a sufficient length of time?
- Are drug interactions interfering?
- Is the patient compliant? Do they understand how to take the medication?
What occurs in drug sensitization?
Clinically manifested as the reverse of tolerance, sensitization is said to occur when sensitivity to a drug effect increases over time. The same dose will produce more pronounced effects over time.
As a general rule, what typically makes a drug more likely to cause significant withdrawal side effects?
More abrupt withdrawal and shorter half life.
Name some common psychiatric medications that have established effects on pregnant women and fetus?
Paroxetine - Increased risk for cardiac malformation
Lithium - Ebstein’s Anomaly (cardiac)
Carbamazepine and Valproic Acid - Neural tube defects
Lamotrigine - oral clefts if used during first trimester
What are the two major concerns when treating geriatric patients with psychiatric drugs?
1) More susceptible to adverse effects (cardiac, dizziness)
2) May metabolize and excrete drugs more slowly thus requiring lower doses.
How does discontinuation of psychotropic drugs affect fall risk?
Reduces by an estimated 40%
How many half lives does it generally take before elimination below clinically relevant levels?
4 to 5 half lives
