Psycho-Pharmacology Flashcards
What are the general pharmacology strategies?
Indication
-Establish a diagnosis and identify the target symptoms that will be used to monitor therapy response
Choice of agent and dosage
-Select an agent with an acceptable side effect profile and use the lowest effective dose. Remember the delayed response for many psych meds and drug-drug interactions.
Management
-Adjust dosage for optimum benefit, safety and compliance. Use adjunctive and combination therapies if needed however always strive for the simplest regime.
What are the indications for antidepressants?
- Unipolar and bipolar depression
- Organic mood disorders
- Schizoaffective disorder
- Anxiety disorders (OCD, panic, social phobia, PTSD)
- Premenstrual dysphoric disorder
- Impulsivity associated with personality disorders
What is selection of antidepressant based on?
- Past history of response
- Side effect profile
- Coexisting medical conditions
How long before symptoms start to improve on antidepressants?
There is a delay typically of 2-4 weeks after a therapeutic dose is achieved before symptoms improve.
What should be done if no improvement is seen on antidepressants?
If no improvement is seen after a trial of adequate length (at least 2 months) and adequate dose, either switch to another antidepressant or augment with another agent.
How should antidepressants be used prophylactically?
- First episode continue for 6mth to a year
- Second episode continue for 2 years
- Third episode discuss life long
What are the classifications of antidepressants?
- Tricyclics (TCAs)
- Monoamine Oxidase Inhibitors (MAOIs)
- Selective Serotonin Reuptake Inhibitors (SSRIs)
- Serotonin/Noradrenaline Reuptake Inhibitors (SNRIs)
- Novel antidepressants
What side effects can TCAs have?
- Antihistaminic, anticholinergic, antiadrenergic
- Lethal in overdose (even 1 week supply can be lethal)
- Prolonged QT complex
Describe the components of tertiary TCAs
- Have tertiary amine side chains
- Have active metabolite including despipramine and nortripytline
Why do tertiary TCAs have more side effects than others?
Side chains are prone to cross react with other types of receptors which leads to more side effects
Give examples of tertiary TCAs.
- Imipramine,
- Amitriptyline
- Doxepin,
- Clomipramine
What are secondary TCAs?
They are often metabolites of tertiary amines
Give examples of secondary TCAs
- Desipramine
- Nortriptyline
What side effects do secondary TCAs have?
Same as tertiary TCAs but less severe
What is the mechanism of secondary TCAs?
Primarily block noradrenaline
What is the mechanism of monoamine oxidase inhibitors?
Bind irreversibly to monoamine oxidase thereby preventing inactivation of amines such as norepinephrine, dopamine and serotonin leading to increased synaptic levels
What are MAOIs particularly effective in?
Resistant depression
What side effects do MAOIs have?
- Orthostatic hypotension
- Weight gain
- Dry mouth
- Sedation
- Sexual dysfunction
- Sleep disturbance
What is the cheese reaction?
Hypertensive crisis can develop when MAOI’s are taken with tyramine-rich foods or sympathomimetics
When can serotonin syndrome develop?
Serotonin Syndrome can develop if take MAOI with meds that increase serotonin or have sympathomimetic actions
What are the symptoms of serotonin syndrome?
- Abdominal pain
- Diarrhoea
- Sweats
- Tachycardia
- HTN
- Myoclonus
- Irritability
- Delirium
- Can lead to hyperpyrexia, cardiovascular shock and death
How is serotonin syndrome avoided?
To avoid need to wait 2 weeks before switching from an SSRI to an MAOI. The exception of fluoxetine where need to wait 5 weeks because of long half-life.
What is the mechanism of SSRIs?
They block presynaptic serotonin reuptake
What are SSRIs used for?
Anxiety and depression symptoms
What side effects do SSRIs have?
- GI upset
- Sexual dysfunction
- Anxiety
- Restlessness
- Nervousness
- Insomnia
- Fatigue or sedation
- Dizziness
- Cardiotoxicity (very little risk in overdose)
What are the symptoms of SSRI associated activation syndrome?
- Nausea
- Increased anxiety
- Panic
- Agitation
Why does activation syndrome occur with SSRIs?
Increase in serotonin
What are the symptoms of SSRI associated discontinuation syndrome?
- Agitation
- Nausea
- Disequilibrium
- Dysphoria
How long can SSRI associated activation syndrome last?
2-10 days
When is SSRI discontinuation syndrome more likely to occur?
More common with shorter half life drugs so consider switching to fluoxetine
What are the advantages of paroxetine?
- Short half life with no active metabolite means no build-up (which is good if hypomania develops)
- Sedating properties (dose at night) offers good initial relief from anxiety and insomnia
What type of drug is paroxetine?
SSRI
What are the disadvantages of paroxetine?
- Sedating, wt gain, more anticholinergic effects
- Likely to cause a discontinuation syndrome
What type of drug is sertraline?
SSRI
What are the advantages of sertraline?
- Very weak P450 interactions (only slight CYP2D6)
- Short half life with lower build-up of metabolites
- Less sedating when compared to paroxetine
What are the disadvantages of sertraline?
- Max absorption requires a full stomach
- Increased number of GI adverse drug reactions
What type of drug is fluoxetine?
SSRI
What are the advantages of fluoxetine?
- Long half-life so decreased incidence of discontinuation syndromes. Good for pts with medication noncompliance issues
- Initially activating so may provide increased energy
- Secondary to long half life, can give one 20mg tab to taper someone off SSRI when trying to prevent SSRI Discontinuation Syndrome
What are the disadvantages of fluoxetine?
- Long half life and active metabolite may build up (e.g. not a good choice in patients with hepatic illness)
- Significant P450 interactions so this may not be a good choice in pts already on a number of meds
- Initial activation may increase anxiety and insomnia
- More likely to induce mania than some of the other SSRIs
What type of drug is citalopram?
SSRI
What are the advantages of citalopram?
- Low inhibition of P450 enzymes so fewer drug-drug interactions
- Intermediate ½ life
What are the disadvantages of citalopram?
- Dose-dependent QT interval prolongation with doses of 10-30mg daily- due to this risk doses of >40mg/day not recommended!
- Can be sedating (has mild antagonism at H1 histamine receptor)
- GI side effects (less than sertraline)
What type of drug is escitalopram?
SSRI
What are the advantages of escitalopram?
- Low overall inhibition of P450s enzymes so fewer drug-drug interactions
- Intermediate 1/2 life
- More effective than Citalopram in acute response and remission
What are the disadvantages of escitalopram?
- Dose-dependent QT interval prolongation with doses of 10-30mg daily
- Nausea, headache
What type of drug is fluvoxamine?
SSRI
What are the advantages of fluvoxamine?
- Shortest ½ life
- Found to possess some analgesic properties
What are the disadvantages of fluvoxamine?
- Shortest ½ life
- GI distress, headaches, sedation, weakness
- Strong inhibitor of CYP1A2 and CYP2C19
What is the mechanism of SNRIs?
Inhibit both serotonin and noradrenergic reuptake like the TCAS but without the antihistamine, antiadrenergic or anticholinergic side effects
What are SNRIs used for?
- Depression
- Anxiety
- Neuropathic pain
What type of drug is venlafaxine?
SNRI
What are the advantages of venlafaxine?
- Minimal drug interactions and almost no P450 activity
- Short half life and fast renal clearance avoids build-up (good for geriatric populations)
What are the disadvantages of venlafaxine?
- Can cause a 10-15 mmHG dose dependent increase in diastolic BP.
- May cause significant nausea, primarily with immediate-release (IR) tabs
- Can cause a bad discontinuation syndrome, and taper recommended after 2 weeks of administration
- Noted to cause QT prolongation
- Sexual side effects in >30%
What type of drug is duloxetine?
SNRI
What are the advantages of duloxetine?
- Some data to suggest efficacy for the physical symptoms of depression
- Thus far less BP increase as compared to venlafaxine, however this may change in time
What are the disadvantages of duloxetine?
- CYP2D6 and CYP1A2 inhibitor
- Cannot break capsule, as active ingredient not stable within the stomach
- In pooled analysis had higher drop out rate
What type of drug is mirtazapine?
Novel antidepressant
What are the advantages of mirtazapine?
- Different mechanism of action may provide a good augmentation strategy to SSRIs. Is a 5HT2 and 5HT3 receptor antagonist
- Can be utilized as a hypnotic at lower doses secondary to antihistaminic effects
What are the disadvantages of mirtazapine?
- Increases serum cholesterol by 20% in 15% of patients and triglycerides in 6% of patients
- Very sedating at lower doses. At doses 30mg and above it can become activating and require change of administration time to the morning.
- Associated with weight gain (particularly at doses below 45mg
What type of drug is buproprion?
Novel antidepressant