Antianxiety drugs


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Antianxiety drugs

  1. 1. Antianxiety drugs Dr. S. Parasuraman M.Pharm., Ph.D., Senior Lecturer, Faculty of Pharmacy, AIMST University, Bedong 08100, Malaysia.
  2. 2. Anxiety • Anxiety It is an emotional state, unpleasant in nature, associated with uneasiness (a fear that seems to arise from a unknown source), discomfort and concern or fear about some defined or undefined future threat. • Some degree of anxiety is a part of normal life. Treatment is needed when it is disproportionate to the situation and excessive. • Some psychotics and depressed patients also exhibit pathological anxiety. • The physical symptoms of severe anxiety are similar to those of fear (such as tachycardia, sweating, trembling, and palpitations) and involve sympathetic activation.
  3. 3. Anxiety
  4. 4. Antianxiety drugs • The anxiolytic-sedative drugs differ from anti psychotics, and more closely resemble sedative-hypnotics. – No therapeutic effect to control thought disorder of schizophrenia – Do not produce extrapyramidal side effects – Have anticonvulsant property – Produce physical dependence and carry abuse liability
  5. 5. Antianxiety drugs Classification • Benzodiazepines: Diazepam, Chlordiazepoxide, Oxazepam, Lorazepam, Alprazolam, Clonazepam, Flurazepam • Azapirones: Buspirone, Gepirone, Ispapirone • Sedative: Hydroxyzine • Barbiturates: Amobarbital, Pentobarbital, Phenobarbital, Thiopental • β blocker: Propranolol • Antidepressants: – Selective serotonin reuptake inhibitors (SSRIs): Fluoxetine, Fluvoxamine, Paroxetine, Escitalopram, Citalopram, Dapoxetine. (effective in obsessivecompulsive Disorder) – Serotonin and noradrenaline reuptake inhibitors (SNRIs): Venlafaxine, Duloxetine. • Benzodiazepine Antagonist: Flumazenil
  6. 6. Benzodiazepines (BZDs)  Agonist at an allosteric site  prolong GABA action  open chloride channel Benzodiazepines are the most widely used anxiolytic drugs. They have largely replaced barbiturates in the treatment of anxiety, because benzodiazepines are safer and more effective.
  7. 7. Benzodiazepines (BZDs) • Benzodiazepines act preferentially on midbrain ascending reticular formation and on limbic system. BZDs act by enhancing presynaptic/postsynaptic inhibition through a specific BZD receptor which is an integral part of the GABAA receptor-Cl- channel complex (GABA receptor has five or more span the postsynaptic membrane). • Benzodiazepines modulate GABA effects by binding to a specific, high-affinity site located at the interface of the α subunit and the γ2 subunit [[Note: These binding site sometimes called as benzodiazepine receptors i.e, BZ1, BZ2]. • Binding of GABA to its receptor triggers an opening of a chloride channel, which leads to an increase in chloride conductance. Benzodiazepines increase the frequency of channel openings produced by GABA (influx of chloride ion cause hyperpolarization).
  8. 8. Benzodiazepines (BZDs) MOM
  9. 9. Benzodiazepines (BZDs) Pharmacological action: • Reduction of anxiety: At low doses, the benzodiazepines are anxiolytic. They are thought to reduce anxiety by selectively enhancing GABAergic transmission in neurons having the α2 subunit in their GABAA receptors, thereby inhibiting neuronal circuits in the limbic system of the brain. • Sedative and hypnotic actions: All of the benzodiazepines used to treat anxiety have some sedative properties, and some can produce hypnosis (artificially produced sleep) at higher doses. Their effects have been shown to be mediated by the α1-GABAA receptors.
  10. 10. Benzodiazepines (BZDs) • Anterograde amnesia: The temporary impairment of memory with use of the benzodiazepines is also mediated by the α1-GABAA receptors. This also impairs a person’s ability to learn and form new memories. • Anticonvulsant: Several of the benzodiazepines have anticonvulsant activity and some are used to treat epilepsy (status epilepticus) and other seizure disorders. This effect is partially, although not completely, mediated by α1-GABAA receptors. • Muscle relaxant: At high doses, the benzodiazepines relax the spasticity of skeletal muscle, probably by increasing presynaptic inhibition in the spinal cord, where the α2- GABAA receptors are largely located. Baclofen is a muscle relaxant that is believed to affect GABA receptors at the level of the spinal cord.
  11. 11. Benzodiazepines (BZDs) Therapeutic uses: • Benzodiazepines show small differences in their relative anxiolytic, anticonvulsant, and sedative properties. • Anxiety disorders: Benzodiazepines are effective for the treatment of the anxiety symptoms secondary to panic disorder, generalized anxiety disorder (GAD), social anxiety disorder, performance anxiety, posttraumatic stress disorder, obsessive-compulsive disorder, and the extreme anxiety sometimes encountered with specific phobias such as fear of flying. • Muscular disorders: Diazepam is useful in the treatment of skeletal muscle spasms, such as occur in muscle strain, and in treating spasticity from degenerative disorders, such as multiple sclerosis and cerebral palsy.
  12. 12. Benzodiazepines (BZDs) Therapeutic uses: • Amnesia: The shorter-acting agents are often employed as premedication for anxiety-provoking and unpleasant procedures such as endoscopic, bronchoscopic, and certain dental procedures as well as angioplasty. • Seizures: Clonazepam is occasionally used in the treatment of certain types of epilepsy, whereas diazepam and lorazepam are the drugs of choice in terminating grand mal epileptic seizures and status epilepticus. • Sleep disorders: Not all benzodiazepines are useful as hypnotic agents, although all have sedative or calming effects. They tend to decrease the latency to sleep onset and increase Stage II of non-rapid eye movement (REM) sleep.
  13. 13. Benzodiazepines (BZDs) Adverse effects: • Drowsiness, sedation, light-headedness, psychomotor and cognitive impairment, vertigo, confusional state (especially in the elderly), increased appetite and weight gain, alterations in sexual function. • Rashes are uncommon. • Some women fail to ovulate while on regular use of BZDs. • The major constraint in their long-term use for anxiety disorders is their potential to produce dependence.
  14. 14. Benzodiazepine antagonist • Flumazenil is a GABA-receptor antagonist that can rapidly reverse the effects of benzodiazepines. • The drug is available for intravenous (IV) administration only. Onset is rapid, but duration is short, with a half life of about 1 hour. Frequent administration may be necessary to maintain reversal of a long-acting benzodiazepine. • Administration of flumazenil may precipitate withdrawal in dependent patients or cause seizures if a benzodiazepine is used to control seizure activity.
  15. 15. Benzodiazepine antagonist Drugs Pharmacological properties Chlordiazepoxide • First BZD to be used clinically. • Oral absorption is slow. • Produces a smooth long lasting effect • Preferred in chronic anxiety states • Its t1/2 is 5-15 hours but active metabolites are produced which extend the duration of action. • It has poor anticonvulsant action. • Dose: 25-100 mg. Diazepam • It is quickly absorbed • t1/2 is 1 hour; elimination phase t1/2 is 20-30 • It is preferred in acute panic states and anxiety associated with organic disease. • Dose: 5-30 mg Oxazepam • It is slowly absorbed • t1/2 is 10 hours • Directly conjugated with glucuronic acid and eliminated • Used mainly in short lasting anxiety states • Dose: 30-60 mg
  16. 16. Benzodiazepine antagonist Drugs Pharmacological properties Lorazepam • Slow oral absorbed, less lipid soluble than diazepam. • t1/2 is 10-20 hours • Directly conjugated with glucuronic acid and eliminated • Quite sedative and capable of producing marked amnesia • Dose: 1-6 mg Alprazolam • High potency anxiolytic BZD which in addition has some mood elevating action in mild depression. • Also used as hypnotic • Dose: 0.25- 1.0 mg
  17. 17. Buspirone • It is the first azapirone, a new class of antianxiety drugs, definitely different from BZDs. – Does not produce significant sedation or cognitive/ functional impairment. – Does not interact with BZD receptor or modify GABAergic transmission. – Does not produce tolerance or physical dependence. – Does not suppress BZD or barbiturate withdrawal syndrome. • Buspirone is useful for the chronic treatment of Generalized Anxiety Disorder (GAD) and has an efficacy comparable to that of the benzodiazepines.
  18. 18. Buspirone- MOA • The mechanism of anxiolytic action is not clearly known, but may be dependent on its selective partial agonistic action on 5-HT1A receptors. By stimulating presynaptic 5-HT1A autoreceptors, it reduces the activity of dorsal raphe serotonergic neurones. Antagonism at certain postsynaptic 3-HT1A receptors has also been demonstrated. • Buspirone has week dopamine D2 blocking action with no antipsychotic or extrapyramidal effects. • Mood elevation may be facilitated by central noradrenergic action.
  19. 19. Buspirone • Pharmacokinetics: – Rapidly absorbed – Undergoes first pass metabolism – Metabolite is active and excreted through both urine and faeces. – t1/2 is 2-3.5 hr; Buspirone has the disadvantage of a slow onset of action. – Side effects: Side effects are minor, dizziness, nausea, headache, – light-headedness and rarely excitement. May increase the BP in patients with MAO inhibitors. – Dose: 5-15 mg
  20. 20. Beta Blockers (adjuvant to BZDs) • Many symptoms of anxiety (palpitation, rise in BP, shaking, tremor, gastrointestinal hurrying, etc.) are due to sympathetic over activity, and these symptoms reinforce anxiety. • Propranolol and other nonselective beta blockers help anxious • patients troubled by these symptoms, by cutting the vicious cycle and provide symptomatic relief. They do not affect psychological symptoms such as worry, tension and fear, but are valuable in acutely stressful situations (examination fear, unaccustomed public appearance, etc.).
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