Clinical psychopharmacology Flashcards
Manfred Joshua Sakel
(therapy, year)
Insulin Coma Therapy for schizophrenia
1934
Ladislas Meduna
(therapy, year)
Convulsive Therapy for schizophrenia (using camphor and metrazol)
1934
Egas Moniz
(therapy, year)
Frontal leucotomy for schizophrenia and depression
1935
Cerletti and Bini
(therapy, year)
Introduced electroconvulsive therapy (ECT) for schizophrenia
1938
Erik Jacobsen + Jens Hald
(drug, year)
Invented Disulfiram in 1948
Initially it was developed as an anthelmintic, then later its use in alcohol dependency was recognised.
John Cade
(drug, year)
Discovered the antimanic effects of Lithium
1949
Frank Berger
(drug, year)
Invented Meprobamate in the 1940s
This was hailed as the first ‘tranquiliser’ in 1954
Paul Charpentier
(drug, year)
Invented Chlorpromazine
1950
Jean Delay + Pierre Deniker
(drug, year)
First used Chlorpromazine to treat psychosis
1952
Who coined the term ‘neuroleptic’
Pierre Deniker with reference to the drug Chlorpromazine, which he first used to treat psychosis in 1952 with Jean Delay
Mahlon Kline
(drug, year)
Isolated Reserpine from the rauwolfia plant in India
1954
Reserpine was prescribed more frequently than chlorpromazine in the 1950s, but its use decreased as it caused akathisia
Roland Kuhn
(drug, year)
Discovered the antidepressant effects of Imipramine - the first tricyclic antidepressant
1955
Paul Janssen (drug, year)
Invented Haloperidol
1958
Leo Sternbach
(drug, year)
Invented chlordiazepoxide (librium) - the first benzodiazepine
1955
Mahlon Kline
(antidepressant, year)
Iproniazid
- the first antidepressant
1957
(The antidepressant effects of isoniazid, an MAOI, had been noted in the 1950s while being used to treat tuberculosis. Iproniazid was invented in 1957 and used effectively to treat depression, but was later withdrawn due to its hepatotoxicity)
John Kane
(drug, year)
Introduced Clozapine into clinical practice for treatment-resistant schizophrenia
1988
======================================================
Clozapine had been invented in 1958 by Fritz Hunziker
Arvid Carlssen
(drug, year)
Synthesised Zimeldine - the first SSRI - in the late 1970s/early 1980s.
This was withdrawn due to it causing hypersensitivity syndrome and demyelinating disease.
Blackwell
(key discovery, year)
First described the ‘cheese reaction’ seen in MAOI-associated hypertension
1963
Who coined the term ‘antidepressant’?
Max Lurie 1953
- with reference to Isoniazid
SSRIs - common adverse effects (5)
GI effects (nausea, D+V, constipation)
Increased risk of GI bleeding
Dizziness
Sexual dysfunction
Hyponatraemia
Which SSRI is preferred in the elderly?
Citalopram - associated with lower risk of drug interactions
Which SSRI is preferred post-MI?
Sertraline
Which SSRI is preferred in children/adolescents?
Fluoxetine
Tricyclic antidepressants - subdivision (2) + difference in mechanisms
1st gen - Tertiary amines
- boost serotonin and noradrenaline.
2nd gen - Secondary amines
- lower side effect profile and act primarily on noradrenaline.
Tricyclic antidepressants - tertiary amines (8)
Amitriptyline
Lofepramine
Imipramine
Clomipramine
Dosulepin (Dothiepin)
Doxepin
Trimipramine
Butriptyline
Tricyclic antidepressants - secondary amines (4)
Protriptyline
Amoxapine
Nortriptyline
Desipramine
‘PAND’
Tricyclic antidepressants - common side effects (5)
drowsiness
dry mouth
blurred vision
constipation
urinary retention
Monoamine Oxidase Inhibitors (MAOI) - subdivision (2)
Irreversible MAOIs (traditional) - ‘PIT’
- Phenelzine
- Isocarboxazid
- Tranylcypromine
Reversible MAOIs
- Moclobemide
(aka RIMA - Reversible Inhibitor of Monoamine oxidase type A)
- less likely to cause cheese reaction than the traditional MAOIs
Serotonin-Noradrenaline Reuptake Inhibitors, SNRI (3)
Venlafaxine
Duloxetine
Milnacipran
Noradrenaline Reuptake Inhibitors, NARI (2)
Reboxetine
Atomoxetine
Dopamine Reuptake Inhibitor, DARI (1)
Bupropion
Serotonin Antagonist and Reuptake Inhibitor, SARI (1)
Trazodone
Noradrenergic and Specific Serotonergic Antagonists, NaSSA (2)
Mirtazepine
Mianserin
Chlorpromazine, Promazine
(structural classification)
Phenothiazine (aliphatic side chain)
Thioridazine, Pipothiazine
(structural classification)
Phenothiazine (piperidine side chain)
Trifluoperazine, Fluphenazine
(structural classification)
Phenothiazine (piperizine side chain)
Haloperidol, Benperidol, Droperidol
(structural classification)
Butyrophenone
Flupenthixol, Zuclupenthixol
(structural classification)
Thioxanthene
Pimozide
(structural classification)
Diphenylbutylpiperidine
Clozapine
(structural classification)
Dibenzodiazepine
Risperidone (structural classification)
Benzoxasole
Olanzapine (structural classification)
Thienobenzodiazepine
Quetiapine (structural classification)
Dibenzothiazepine
Sulpride, Amisulpride (structural classification)
Substituted benzamide
Aripiprazole (structural classification)
Arylpiperidylindole (quinolone)
Tricyclic antidepressant considered least toxic in overdose
Lofepramine
Tricyclic antidepressants considered most toxic in overdose (2)
Amitriptylline
Dosulepin
Clozapine - indications
NICE guidelines recommend the use of clozapine to people with schizophrenia whose illness has not responded adequately to treatment despite the sequential use of adequate doses of at least two different antipsychotic drugs.
They stipulated that at least one of the drugs should be a non-clozapine second-generation antipsychotic.
Clozapine (levels)
The average clozapine dose in the UK is 450 mg/day.
A ‘therapeutic range’ has not been established. It is generally accepted that a level of 350 µg/L is necessary to achieve a therapeutic response.
Levels greater than 500 µg/L should be treated with caution as there is a risk of seizures.
Lower doses may be required in non-smokers, the elderly, females, and in patients using enzyme inhibitors (e.g. SSRI’s). Treatment should of course be guided by clinical response (treat the patient not the level).
Clozapine - common side effects (8)
Drowsiness/ sedation
Dizziness
Insomnia
Salivation
Nausea + Vomiting
Dyspepsia
Weight gain
Constipation
Clozapine - adverse effects (10)
Agranulocytosis
Myocarditis
Seizures
Severe orthostatic hypotension with or without syncope
Increased mortality in elderly patients with dementia related psychosis
Colitis
Pancreatitis
Thrombocytopenia
Thromboembolism
Insulin resistance and diabetes mellitus
==========================================
(Approx 33 percent developed diabetes mellitus over a ten year period (Henderson, 2005)) The BNF advices caution in the following circumstances: prostatic hypertrophy susceptibility to angle-closure glaucoma adult over 60 years
Clozapine - agranulocytosis
(prevalence, timing, rechallenge)
Agranulocyotosis occurs in 1-2% of patients on clozapine
It is more common in the first 18 weeks of treatment
One-third of patients who stop clozapine due to neutropenia or agranulocytosis will develop a blood dyscrasia on rechallenge.
In most cases, the second reaction will occur more rapidly, be more severe, and will last longer than the first
Clozapine - agranulocytosis (treatment)
Lithium has been shown to independently raise the white cell count and has been used in this way successfully in combination with clozapine. Use of this combination can enable patients to continue on treatment when they develop neutropenia.
Having said that there are case reports suggesting that the combined use of lithium and clozapine can result in toxicity and so this combination must be used with caution.
Clozapine - augmentation (favoured drugs)
Sulpride and amisulpride are the favoured antipsychotics for augmentation with clozapine as their selectivity for D2 dopamine blockade compliments clozapine (which lacks high potency dopamine blockade).
Lamotrigine has the best evidence of the mood stabilisers to support its use as an augmentation strategy.
Atypical antipsychotics available in depot form (3)
Olanzapine
Aripiprazole
Risperidone - Risperdal Consta or Paliperidone
‘OAR’
Lithium (therapeutic index)
0.4 - 1.2 mmol/L
Lithium - side effects (10)
Drowsiness
Dry mouth
Polyuria
Polydipsia
Metallic taste
Muscle weakness
GI - Nausea + Diarrhoea
Weight gain
Fine tremor
Worsening of psoriasis
Lithium - long-term adverse effects (4)
Hypothyroidism
Irreversible nephrogenic diabetes insipidus
Reduced GFR (chronic kidney disease)
Hyperparathyroidism
Drugs that increase lithium levels (3)
NSAIDs/COX-2 inhibitors
ACE inhibitors
Thiazide diuretics
====================================
NB: Loop diuretics (furosemide) generally have no effect on lithium levels
Lithium
- teratogenic effect
- risk
- increased risk from general population
Cardiac (Ebstein’s) anomalies
The risk of Ebstein’s in women taking lithium is 1 in 1000
(which is 20 times the normal level).
Carbamazepine (mechanism of action)
binds to sodium channels increases their refractory period
Carbamazepine - adverse effects (8)
P450 enzyme inducer
dizziness and ataxia
drowsiness
headache
visual disturbances (especially diplopia)
Steven-Johnson syndrome
leucopenia and agranulocytosis
syndrome of inappropriate ADH secretion (hyponatraemia)
Carbamazepine (teratogenic effect)
Fingernail hypoplasia, craniofacial defects
Valproate (mechanism of action)
GABA agonist
NMDA antagonist
Valproate - forms (3, + indications)
1 - Semi-sodium valproate (Depakote) (licensed for acute mania associated with bipolar disorder)
2 - Valproic acid (licensed for acute mania associated with bipolar disorder)
3 - Sodium valproate (licensed for epilepsy)
[Note that the BNF 61 is not consistent with the Maudsley Guidelines 10th Edition which suggest valproic acid is not licensed for acute mania.]
Valproate (teratogenic effect)
Spina bifida, hypospadias
Valproate - key adverse effects (4)
Tiredness
Significant weight gain (30-50% of patients)
Tremor (up to 25% of patients)
Hair loss (5% to 10% of patients, with curly regrowth once valproate is stopped)
Topiramate (mechanism of action)
GABA agonist
NMDA antagonist
Na channel stabiliser
Topiramate (use)
Refractory or rapid cycling bipolar affective disorder where lithium plus valproate has been ineffective
Phenytoin (mechanism of action)
binds to sodium channels increasing their refractory period
Phenytoin (teratogenic effects - 4)
Craniofacial defects
limb defects
cerebrovascular defects
mental retardation
Phenytoin (chronic adverse effects - 7)
gingival hyperplasia (secondary to increased expression of platelet derived growth factor, PDGF)
hirsutism
coarsening of facial features
drowsiness
megaloblastic anaemia (2ndary to altered folate metabolism) peripheral neuropathy osteomalacia (enhanced vitamin D metabolism)
lymphadenopathy
dyskinesia
Benzodiazepines (mechanism of action)
Potentiation of the GABA inhibitory effect on the CNS by increasing the number and frequency of chloride channel opening
Benzodiazepines (pharmacokinetics)
- absorbed well following oral administration
- they show high plasma protein binding (95% for diazepam)
- mainly metabolised in the liver
- they tend to be highly lipophilic and rapidly cross the blood brain barrier and placental barrier
Diazepam (half-life)
20-100 hours
Clonazepam (half-life)
18-50 hours
Chlordiazepoxide (half-life)
5-30 hours
Nitrazepam (half-life)
15-38 hours
Temazepam (half-life)
8-22 hours
Lorazepam (half-life)
10-20 hours
Alprazolam (half-life)
10-15 hours
Oxzazepam (half-life)
6-10 hours
Zopiclone (half-life)
5-6 hours
Zolpidem (half-life)
2 hours
(SPMM states 1-3 hours)
Zaleplon (half-life)
2 hours
(SPMM states 1 hour)
Buspirone (mechanism of action)
5HT1A partial agonist
Licensed for the short-term management of anxiety
Who coined the term ‘placebo effect’?
Henry K. Beecher (1955)
Active placebo (definition)
a drug which has its own inherent effects but none for the condition for which it is being given.
e.g. the use of atropine as the control drug in trials of antidepressants.
Factors that increase placebo response
- Injections > oral
- brighter coloured tablets
- larger tablets
- status of the treating professional
- branded > unbranded
Placebo response - pattern analyses
Pattern analyses have shown that the improvement as a result of placebo in depression tends to be abrupt, occurs early in treatment and is less likely to persist, whereas improvement in response to antidepressants tends to be gradual, occurs later and is more likely to persist.
Placebo sag (essence)
a situation where the placebo effect is diminished (attenuated) with repeated use
Placebo response rate (%) in - depression - schizophrenia
Depression - 60%
Schizophrenia - 30%
Drug approval process (5 steps)
Animal studies
Phase 1 clinical trials - safety
Phase 2 clinical trials - effectiveness
Phase 3 clinical trials - superiority
Phase 4 clinical trials - post-marketing surveillance
… clinical trials involve only a small number of healthy people (possibly as few as 15-20). The focus is to evaluate the drugs safety, determine a safe dosage range, and identify side effects.
Phase 1
In … clinical trials the drug or treatment is given to a larger group of people (100-300) to see if it is effective and to further evaluate its safety.
Phase 2
In … trials the drug or treatment is given to large groups of people (1,000-3,000) to confirm its effectiveness, monitor side effects, compare it to commonly used treatments (or placebos), and collect information that will allow the experimental drug or treatment to be used safely.
Phase 3
are done after the drug has been granted a license. They gather further information on the drug in areas not addressed in the previous trials (e.g. Safety in pregnancy) and also to find other potential uses for the drug.
Phase 4 (post-marketing trials)
Pharmacokinetics - core components (4)
Absorption
Distribution
Metabolism
Elimination
‘ADME’
Absorption (definition)
The process by which a drug enters the bloodstream
What route of administration yields the fastest absorption?
Inhalation
Bioavailability (definition)
the fraction of an administered dose of a drug that reaches the systemic circulation in an unchanged form
(by definition, when a medication is administered intravenously, its bioavailability is 100%)
Distribution (definition + two key factors)
the reversible transfer of a drug from one location to another within the body
2 important factors affecting this are:
- tissue perfusion
- drug lipophilicity
Metabolism (definition)
the biotransformation of compounds into new compounds, in order that they are made more water-soluble and can be more easily excreted from the body
Elimination (definition)
how a drug is removed from the body, whether unaltered or in the form of its metabolites
First-pass metabolism (aka, definition)
aka prehepatic/presystemic metabolism
the intestinal and hepatic degradation or alteration of a drug or substance taken by mouth, after absorption, that removes some of the active substance from the blood before it enters the general circulation
Plasma half-life (definition)
the time taken to eliminate 50% of the absorbed dose of a drug from a person’s plasma
Biological half-life (definition)
the time taken for a drug to lose half of its pharmacologic activity
Clearance (definition)
the volume of plasma (or blood) from which the drug is completely removed, or cleared, in a given time period
[aka renal clearance or renal plasma clearance where referring specifically to the kidneys]
Blood brain barrier (definition, key facts)
a barrier separating the circulating blood flow in the human body from the extracellular fluid in the brain.
- it consists of capillary endothelial cells tightly packed together
- lipid soluble molecules pass through relatively easily whereas water soluble ones do not
- Large molecules do not pass through the easily
- Molecules that are highly charged struggle to pass through
- The permeability of the BBB increases when it is inflamed
- Nasally administered drugs can theoretically bypass the BBB
- At several areas the BBB is fenestrated to allow neurosecretory products to enter the blood
- Posterior pituitary
- Area postrema
Cytochrome P450 system (essence)
- an evolved mechanism that deals with exogenous toxins and is therefore essential in the metabolism of drugs
- comprises about fifty separate enzymes
- the enzymes are located on the endoplastic reticulum of cells and are mainly found in the liver and small intestine
Which Cytochrome P450 enzyme is involved in the metabolism of clozapine?
CYP1A2
Grapefruit juice
(interaction with the Cytochrome P450 system, drugs affected)
Inhibits CYP3A4
Increases levels of:
- carbamazepine
- benzos: diazepam, nitrazepam
- neuroleptics: aripiprazole, quetiapine
- antidepressants: sertraline, trazodone
Inhibits CYP1A2
Increases levels of:
- clozapine
Caffeine
(interaction with the Cytochrome P450 system, drugs affected)
Inhibits CYP1A2
Increases levels of:
- clozapine
Tobacco
(interaction with the Cytochrome P450 system, drugs affected)
Induces CYP1A2
Reduces levels of:
- clozapine
- olanzapine
- fluvoxamine
Steady state (essence)
This refers to the situation where the intake of a drug is at the same overall rate as its elimination from the body, so that there is no net change in the amount of drug in the person’s system.
It is usually reached after 4-5 times the half-life of the drug has elapsed after commencement of regular dosing.