Antianxiety Drugs
Antianxiety Drugs
Benzodiazepines (BD) – the most effective antianxiety drugs
Antidepressants
–Selective serotonin reuptake inhibitors (SSRIs)
–Tricyclic antidepressants (TCAs)
–Heterocyclics
- Mixed norepinephrine/serotonin reuptake inhibitors
- Mixed-action drugs
–Monoamine oxidase inhibitors (MAOIs)
- Buspirone
- Antipsychotics (neuroleptics)
- Barbiturates
- Antihistamines
- Clonidine
- Beta-blockers
- Meprobamate and derivatives
- Antiepileptic drugs
- Alcohol
Benzodiazepines (BD)
Mechanism of action:
- Facilitate neuronal membrane inhibition by actions as specific receptors
- Binds to specific receptors in CNS that are involved in modulation of GABA (γ-aminobutyric acid) transmission (enhancement of affinity of GABA)
- This inhibitory neurotransmitter increses the influx of chloride ions through cell membrane channels, thus inhibiting membrane depolarization
- BD do not substitute for GABA but appear to enhance GABA’s effects without directly activating GABA receptors or opening the associated chloride channels
- The enhancement in chloride ion conductance induced by the interaction of BD with GABA takes the form of an increase in the frequency of chanel-opening events
- Receptors for BD – in many brain regions (thalamus, limbic structures, cerebral cortex)
Short-acting BD: •Midazolam •Lorazepam •Oxazepam •Alprazolam •Halazepam
Long-acting BD: •Diazepam •Chlordiazepoxide •Chlorazepate •Prazepam •Clonazepam
Administration
- They are best used only for brief periods (psychological and physiological dependence, tolerance)
- The best results – treating time-limited anxiety (in response to clear-cut stress and when treatment lasts less than 8 weeks)
- Chronic anxiety, limited intrapsychic or external resources, inefficacy of buspirone and antidepressants – may need long-term therapy
- Repeated treatment – often necessary
Addiction
- Is rare in medical patients
- Individuals with a history of alcohol or drug abuse, physician shopping, antisocial behavior – are at risk of abusing BD
- The most frequently abused BD: •diazepam •alprazolam •lorazepam
Adverse effects
– sedation, impaired cognitive defects (difficulty focusing attention, memory impairment, confusion), disinhibition, tolerance, abuse potential, withdrawal, may cause or aggravate depression
Abstinence syndromes (withdrawal symptoms)
- May appear up to 10 days after abrupt discontinuation of moderate doses of BD that have been taken for more than 1 month
- Anxiety, insomnia, irritability, at times psychosis, delirium, seizures
- Some patients – withdrawal symptoms lasting up to 1 year
- Withdrawal is more abrupt and severe after discontinuation of short-acting BD•
SSRIs
: Fluoxetine •Sertraline •Paroxetine •Fluvoxamine •Citalopram •Escitalopram
Side effects: headache, nausea and other gi effects, jitteriness, insomnia, sexual dysfunction, can affect plasma levels of other meds, akathisia rare
TCAs
: Amitryptyline, Nortriptyline, Imipramine, Desipramine, Doxepin, Clomipramine
Side effects: anticholinergic (dry mouth, tachycardia, constipation, urinary retention, blurred vision), sweating, tremor, postural hypotension, cardiac conduction delay, sedation, weight gain
Mixed norepinephrine/serotonin reuptake inhibitors •Venlafaxine •Mirtazapine
Side effects: nausea, dizziness, dry mouth, headaches, increased blood pressure, anxiety and insomnia, somnolence, weight gain, neutropenia rare
Mixed-action drugs: •Bupropion •Trazodone •Nefazodone •Amxapine
Side effects:
jitteriness, flushing, seizures in at-risk patients, anorexia, tachycardia, psychosis, sedation, dry mouth, ventricular irritability, postural hypotension, priapism rare, headaches, dry mouth, nausea, constipation, sexual dysfunction
Buspiron
Mechanism of action:
- Unclear
- May involve alteration of dopaminergic or serotinergic activity in CNS (partial agonist of the serotonin 5-HT1Areceptor)
- Nonsedating, doas’nt produce tolerance or dependence, doas’nt interact with BD receptor or alcohol
- Takes 1 month lag time before clinical response
;Requires thrice-daily dosing
Indications:
the same as the BD, generalized anxiety disorder, social phobias
Adverse effects: minimal sedation, nausea, headache, psychomotor impairment
Barbiturates
Effective sedative-hypnotics; Impairment of motor and intellectual performance; Interact with many drugs; High fatality rate with overdoses; High addiction potential
- Facilitate the actions of GABA at multiple sites in the CNS, but (in cotrast to BD) appear to increase the duration of the GABA-gated chloride channel openings
- At high concentrations may also be GABA-mimetic, directly activating chloride channels
- These effects involve a binding site (sites) distinct from BD binding site
- Also depress the actions of excitatory neurotransmitters (eg glutamic acid)
Antihistamines
- Hydroxizine – limited usefulness as a pre-anesthetic sedative (patients who do not respond to BD), Diphenhydramine
- Usually with effective dosage – sedation, increase muscle tone, lower seizure threshold, affect the peripheral nervous system
Antipsychotics
Not cosistently effective in treating anxiety; Seldom used to treat anxiety
Anticonvulsants
- GABAergic properties (gabapentin, oxcarbazepine, tiagabine, pregabalin, divalproex)
Beta-blokers
Effective in preventing performance anxiety by suppressing sympathetic nervous system activity and autonomic symptoms (palpitations, tremor);
Ineffective in preventing the emotional symptoms
Clonidine
Acts by decreasing the firing of locus ceruleus.
Side effects: dry mouth, increased tension, drowsiness, sleep disturbances;
Meprobamate and derivatives
- Muscle relaxant properties, sedative and anticonvulsant activity; Induce liver microsomal enzymes; Tolerance, dependence
Alcohol – The most common self-prescribed anxiolytic agent
- It is not recommended for use in the treatment of anxiety disorders (alcoholism)
Source: http://www.farmakologia.ump.edu.pl/attachments/
article/35/sedative%20and%20antianxiety%20~.doc
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