L5-6 Antidepressants Flashcards
If a patient is on an antihypertensive drug already, which of the TCAs is the best to give?
Nortriptyline
would not contribute to an even lower BP (through alpha blockade)
What are the uses of TCAs?
Depression
Panic Disorder
Pain
Fibromyalgia
Enuresis-Imipramine
ADHD
Name the TCA tertiary amines.
What is significant about them?
Imipramine
Amitriptyline
Trimipramine
Doxepin
- more sedating than secondary amines
- more serotonin effect
Name the TCA secondary amines.
What is significant about them?
Desipramine
Nortriptyline
Protriptyline
- less sedating
- more NE effect
What are the two TCA drugs you would NOT want to give in patients with pre-existing cardiac problems?
Imipramine (tertiary) and desipramine (secondary)
What is the mechanism of action of the TCAs?
What are the three receptors do TCAs block?
TCAs inhibit the uptake of NE and serotonin.
Histamine blockade: drowsiness and sedation, tolerance develops in 1 wk
Muscarinic blockade (anti-cholinergic): impairment of memory and cognition
Alpha blockade: postural hypotension, dizziness, reflex tachycardia
What are the autonomic effects of the TCAs?
With with TCAs are these most likely to be seen?
Cholinergic blockade: blurred vision, tachycardia, palpitations, constipation, urinary retention, dry mouth, metallic taste, gastric distress
More common with the tertiary compounds.
Why do the TCAs cause analgesia?
Due to a direct action of descending noradrenergic pathways in the spinal cord, activating endorphin neurons in the dorsal horn. This, in turn, decreases release of Substance P.
What are the cardiac effects of the TCAs?
Most common: orthostatic hypotension and tachycardia due to **alpha blockade and anti-cholinergic effects. **Can potentiate effect of antihypertensives.
Cardiac depression (more severe in patients with conduction defects or on Class I anti-arrythmatics)
Increased irritability
Can lead to ventricular arrhythmias (Torsades de pointes), can see inverted or flattened T waves
What patients should never be given TCAs?
Previous MI
BBB
Use caution in: seizure patients (decrease seizure threshold), patients with cardiac problems or who are on antiarrythmatics
What are the CNS effects of TCAs?
Sedation, drowsiness (histamine blockade)
Weakness, fatigue
Worse with tertiary TCAs
Anti-cholinergic: delirium at toxic doses
What are some side effects of TCAs that are not autonomic, cardiac, or CNS related?
weight gain
decreases the seizure threshold
SIADH: water intoxication, hyponatremia
Sexual dysfunction
Some physical dependence: muscle aches and malaise if stopped abruptly
Can TCAs be used in pregnancy?
YES
What are some basic pharmacokinetic principles with the TCAs?
Well absorbed orally
Long half-lives
Significant protein binding
Metabolized in liver-interactions common
What are the effects of a TCA overdose?
Cardiac conduction defects and arrythmias-torsades de pointes
Severe hypotension
Agitation, delirium
Neuromuscular irritability and seizures
Hyperpyrexia
Coma, shock, metabolic acidosis
Respiratory depression
How do you treat a TCA overdose?
Cardiac monitoring, supportive care
Gastric lavage, charcoal
Magnesium, isoproterenol, cardiac pacing for torsades de pointes
Lidocaine, propranolol, phenytoin to manage arrythmias and seizure prevention
Sodium bicarb and potassium chloride to restore acid base balance
What is the big drug interaction with TCAs?
MAOIs = serotonin syndrome: CNS toxicity, hyperpyrexia, convulsions, coma
SSRIs= compete for metabolism-toxic levels
Clonidine: decrease effectiveness–>leads to hypertension
Amphetamines: hypertension
Potentiate effects of other CNS depressants and alcohol
What is Clomipramine?
A TCA approved for use in OCD. Works similarly to SSRIs.
What is the mechanism of action of MAOIs?
Inhibits MAO-A and MAO-B
Monoamine oxidase enzymes breaks down circulating catecholamines and compounds ingested from food (tyramine)
MAO-A breaks down NE and serotonin
MAO-B breaks down DA
Name the two MAOIs.
What are they used to treat typically?
Phenelzine and tranylcypromine both irreversibly inhibit borth MAO-A and MAO-B
Useful in aytpical depression that hasn’t responded to other drugs
Drug of last choice due to serious side effects
What are the pharmacokinetics of the MAOIs?
metabolized in liver
effects persist for 1-3 weeks after discontinuing the drug due to long half-lives and irreversible inhibition of MAO
What is the big dangerous side effect of the MAOIs?
HYPERTENSIVE CRISIS!
Irreversible inhibition of MAO in the GI tract allows accumulation of tyramine ingested in food
Tyramine causes release of catecholamines from nerve endings and adrenal medulla
Ingestion of foods containing tyramine can lead to severe hypertensive crisis which can produce fatal intracranial bleeding
Can also occur if MAOIs are taken with sympathomimetic drugs
Treated with alpha receptor blocker: phentolamine
What are some drug interactions with the MAOIs?
OTC cold and cough meds: anything containing sympathomimetic amines such as phenyleprine, ephedrine, or amphetamines–>severe hypertension
TCAS or SSRIs–>serotonin syndrome
Meperidine, tramadol, dextromethorphan–>serotonin syndrome
Buspirone–>hypertension
USE CAUTION WITH ALL MEDICATIONS
What does a MAOI overdose look like?
agitation, hallucinations, hyperreflexia, hyperpyrexia, convulsions, hypo or hypertension