Antianxiety Drugs

Antianxiety Drugs

Benzodiazepines (BD) – the most effective antianxiety drugs

Antidepressants

–Selective serotonin reuptake inhibitors (SSRIs)

–Tricyclic antidepressants (TCAs)

–Heterocyclics

  • Mixed-action drugs

–Monoamine oxidase inhibitors (MAOIs)

  • Buspirone
  • Antipsychotics (neuroleptics)
  • Barbiturates
  • Antihistamines
  • Clonidine
  • Beta-blockers
  • Meprobamate and derivatives
  • 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

Short-acting BD: •Midazolam  •Lorazepam  •Oxazepam  •Alprazolam  •Halazepam

Long-acting BD: •Diazepam  •  •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
  • 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, , insomnia, , can affect plasma levels of other meds, akathisia rare

TCAs

: Amitryptyline, Nortriptyline, , Desipramine, Doxepin,

Side effects: anticholinergic (, 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  •  •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

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

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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