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(Hydroxyzine (Vistaril, Atarax))
(Introduction)
 
(12 intermediate revisions by the same user not shown)
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==Introduction==
 
==Introduction==
 +
This article provides clinical information about first-generation antihistamines commonly used in psychiatry, '''diphenhydramine (Benadryl)''' and '''hydroxyzine (Vistaril)''',  '''cyproheptadine''' and doxylamine (Diclegis). This article does not cover allergy-related and antiemetic properties of antihistamines.
 +
 +
==Background==
 +
 
All medications designated as '''antihistamines''' are strong antagonists or inverse agonist at the peripheral and central histamine receptors.  
 
All medications designated as '''antihistamines''' are strong antagonists or inverse agonist at the peripheral and central histamine receptors.  
* Blockade or the inverse agonism of the '''peripheral H-1 receptor''' alleviates allergy symtpoms.
+
* Blockade or the inverse agonism of the '''peripheral H-1 receptor''' alleviates allergy symtptoms.
 
* Blockade or inverse agonism of the '''central H-1 receptor''' increases sedation.
 
* Blockade or inverse agonism of the '''central H-1 receptor''' increases sedation.
 
* Second-generation antihistamines do not cross the blood-brain barrier, and thus are '''not sedating, do not diminish anxiety or act as anti-emetics'''.
 
* Second-generation antihistamines do not cross the blood-brain barrier, and thus are '''not sedating, do not diminish anxiety or act as anti-emetics'''.
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* Benadryl is '''generally safe in pregnancy''' (Category B), but is excreted in breast milk.
 
* Benadryl is '''generally safe in pregnancy''' (Category B), but is excreted in breast milk.
 
* It can prolong QTc interval in large doses or in combination with other QTc-prolonging medications.
 
* It can prolong QTc interval in large doses or in combination with other QTc-prolonging medications.
* It is possible to be allergic to Benadryl. Benadryl can also worsen '''restless leg syndrome'''
+
* It is possible to be allergic to Benadryl; Benadryl can also worsen '''restless leg syndrome'''
  
 
==Hydroxyzine (Vistaril, Atarax) ==
 
==Hydroxyzine (Vistaril, Atarax) ==
 
*Vistaril is another first generation antihistamine commonly used in psychiatry. It is just as sedating as Benadryl (if not more), but has fewer anti-cholinergic effects. It '''should not''' be used for treating EPS or dystonic reactions of anti-psychotics.
 
*Vistaril is another first generation antihistamine commonly used in psychiatry. It is just as sedating as Benadryl (if not more), but has fewer anti-cholinergic effects. It '''should not''' be used for treating EPS or dystonic reactions of anti-psychotics.
 
* Just like Benadryl, it is widely used in child psychiatry for sleep and as PRN in behavioral emergencies.  
 
* Just like Benadryl, it is widely used in child psychiatry for sleep and as PRN in behavioral emergencies.  
* Vystaril acts on 5-HT2a receptor which justifies its clinical use in generalized anxiety disorder. This is supported by at least one RCT. (2)
+
* Vistaril acts on 5-HT2a receptor which justifies its clinical use in generalized anxiety disorder. This is supported by at least one RCT. (2)
** A [[http://www.ncbi.nlm.nih.gov/pmc/articles/PMC446220|REVIEW]]: 5HT-2a is a '''post-synaptic serotonin receptor (do not confuse with 5-HTT, a pre-synaptic serotonin transporter, the primary target of SSRIs); '''blockade of 5HT-2a''' is an important property of second-generation antipsychotics, Vistaril, Remeron and Trazadone. SSRIs have a long-term effect on 5-HT-2a receptor. Hallucinogen '''LSD''' is a 5HT-2A agonist.
+
** A REVIEW [http://www.ncbi.nlm.nih.gov/pmc/articles/PMC446220]: 5HT-2a is a '''post-synaptic serotonin receptor''' (do not confuse with 5-HTT, a pre-synaptic serotonin transporter, the primary target of SSRIs); '''blockade of 5HT-2a''' is an important property of second-generation antipsychotics, Vistaril, Remeron, and Trazadone. SSRIs have a long-term effect on 5-HT-2a receptor. Hallucinogen '''LSD''' is a 5HT-2A agonist.
 +
 
 +
==Cyproheptadine==
 +
Cyproheptadine is a first generation antihistamine with considerable '''antiserotonergic''' properties.
 +
Cyproheptadine is used for:
 +
* treatment of nightmares including nightmares related to PTSD.
 +
* management of moderate to severe cases of serotonin syndrome
 +
* SSRI-induced sexual dysfunction
 +
* drug-induced hyperhidrosis
 +
* prevention of pediatric migraines
 +
* [[Anorexia Nervosa|anorexia nervosa]]
 +
 
 +
==Doxylamine==
 +
Doxylamine is another old first-generation antihistamine; it's relevant here, because doxylamine is believed to be a better alternative to Benadryl in pregnant women as a sleep aid.
 +
* it still has potent anti-cholinergic effects as thus can cause  dry mouth, ataxia, urinary retention, and drowsiness.
 +
* '''Diclegis'''  (doxylamine + Vitamin B6, extended release preparation) was recently approved by the FDA to treat pregnant women experiencing nausea and vomiting or '''morning sickness''' (Pregnancy Category A)
  
 
== Black Belt facts ==
 
== Black Belt facts ==
* Benadryl was discovered and FDA-approved in 1940s; in 1960s it was discovered that it inhibits serotonin reuptake (inhibits the serotonin transporter, 5-HTT). This eventually led to discovery of Prozac, the first SSRI.  
+
* Benadryl was discovered and FDA-approved in 1940s; in 1960s it was discovered that Benadryl inhibits serotonin reuptake (i.e. blocks the serotonin transporter, 5-HTT). This eventually led to discovery of Prozac, the first SSRI.  
 
** This also means that Benadryl can contribute to a serotonin toxicity, particularly when combined with other serotonergic drugs.
 
** This also means that Benadryl can contribute to a serotonin toxicity, particularly when combined with other serotonergic drugs.
* Most antihistamines undergo hepatic metabolism; one of Vistaril's metabolites is '''cetirizine''', a second-generation antihistamine. Ceterizine is excreted in urine.
+
* Most antihistamines undergo hepatic metabolism; one of Vistaril's metabolites is '''cetirizine''', a second-generation antihistamine. Cetirizine is excreted in urine.
* Vystaril is a pamoate salt of hydroxyzine, while Atarax is a hydrochloride salt of hydroxyzine. This difference in preparations has no clinical significance.
+
* Vistaril is a pamoate salt of hydroxyzine, while Atarax is a hydrochloride salt of hydroxyzine. This difference in preparations has no clinical significance.
 +
 
 +
==References==
 +
1. Pau Celada, M. Victoria Puig, et.al. The therapeutic role of 5-HT1A and 5-HT2A receptors in depression J Psychiatry Neurosci. 2004 Jul; 29(4): 252–265. <br>
 +
 
 +
2. Llorca PM; Spadone C; Sol O et al. Efficacy and safety of hydroxyzine in the treatment of generalized anxiety disorder: a 3-month double-blind study. J Clin Psychiatry 2002, 63 (11): 1020–7. doi:10.4088/JCP.v63n1112. PMID 12444816 <br>
  
References
+
3. Kubo N, Shirakawa O, Kuno T, et al. Antimuscarinic effects of antihistamines: quantitative evaluation by receptor-binding assay. Jpn J Pharmacol. 1987;43:277-282 </br>
1. Kubo N, Shirakawa O, Kuno T, et al. Antimuscarinic effects of antihistamines: quantitative evaluation by receptor-binding assay. Jpn J Pharmacol. 1987;43:277-282 </br>
+
2. Llorca PM; Spadone C; Sol O et al. "Efficacy and safety of hydroxyzine in the treatment of generalized anxiety disorder: a 3-month double-blind study" (PDF). J Clin Psychiatry 2002, 63 (11): 1020–7. doi:10.4088/JCP.v63n1112. PMID 12444816
+
  
 
[[Category: Medications]]
 
[[Category: Medications]]
 +
{{completeness}}

Latest revision as of 12:55, 2 October 2016

Introduction

This article provides clinical information about first-generation antihistamines commonly used in psychiatry, diphenhydramine (Benadryl) and hydroxyzine (Vistaril), cyproheptadine and doxylamine (Diclegis). This article does not cover allergy-related and antiemetic properties of antihistamines.

Background

All medications designated as antihistamines are strong antagonists or inverse agonist at the peripheral and central histamine receptors.

  • Blockade or the inverse agonism of the peripheral H-1 receptor alleviates allergy symtptoms.
  • Blockade or inverse agonism of the central H-1 receptor increases sedation.
  • Second-generation antihistamines do not cross the blood-brain barrier, and thus are not sedating, do not diminish anxiety or act as anti-emetics.

Diphenhydramine (Benadryl)

  • Benadryl is a first-generation antihistamine; in addition to blocking H-1 receptors, it is a potent anti-cholinergic drug (blocks muscarinic receptors) and therefore can be used to mitigate extrapyramidal effects of antipsychotics, and has a role in treatment of Parkinson's disease. As noted above, it crosses the blood-brain barrier, and thus quite sedating
    • Its use is generally avoided in the elderly due to significant sedation (risk of falls) and potential for anti-cholinergic toxicity (dry mouth, tachycardia, urinary retention, and delirium)
  • Benadryl is frequently used in inpatient child psychiatry as a PRN medication (PO or IM) for its sedating properties.
  • Benadryl is generally safe in pregnancy (Category B), but is excreted in breast milk.
  • It can prolong QTc interval in large doses or in combination with other QTc-prolonging medications.
  • It is possible to be allergic to Benadryl; Benadryl can also worsen restless leg syndrome

Hydroxyzine (Vistaril, Atarax)

  • Vistaril is another first generation antihistamine commonly used in psychiatry. It is just as sedating as Benadryl (if not more), but has fewer anti-cholinergic effects. It should not be used for treating EPS or dystonic reactions of anti-psychotics.
  • Just like Benadryl, it is widely used in child psychiatry for sleep and as PRN in behavioral emergencies.
  • Vistaril acts on 5-HT2a receptor which justifies its clinical use in generalized anxiety disorder. This is supported by at least one RCT. (2)
    • A REVIEW [1]: 5HT-2a is a post-synaptic serotonin receptor (do not confuse with 5-HTT, a pre-synaptic serotonin transporter, the primary target of SSRIs); blockade of 5HT-2a is an important property of second-generation antipsychotics, Vistaril, Remeron, and Trazadone. SSRIs have a long-term effect on 5-HT-2a receptor. Hallucinogen LSD is a 5HT-2A agonist.

Cyproheptadine

Cyproheptadine is a first generation antihistamine with considerable antiserotonergic properties. Cyproheptadine is used for:

  • treatment of nightmares including nightmares related to PTSD.
  • management of moderate to severe cases of serotonin syndrome
  • SSRI-induced sexual dysfunction
  • drug-induced hyperhidrosis
  • prevention of pediatric migraines
  • anorexia nervosa

Doxylamine

Doxylamine is another old first-generation antihistamine; it's relevant here, because doxylamine is believed to be a better alternative to Benadryl in pregnant women as a sleep aid.

  • it still has potent anti-cholinergic effects as thus can cause dry mouth, ataxia, urinary retention, and drowsiness.
  • Diclegis (doxylamine + Vitamin B6, extended release preparation) was recently approved by the FDA to treat pregnant women experiencing nausea and vomiting or morning sickness (Pregnancy Category A)

Black Belt facts

  • Benadryl was discovered and FDA-approved in 1940s; in 1960s it was discovered that Benadryl inhibits serotonin reuptake (i.e. blocks the serotonin transporter, 5-HTT). This eventually led to discovery of Prozac, the first SSRI.
    • This also means that Benadryl can contribute to a serotonin toxicity, particularly when combined with other serotonergic drugs.
  • Most antihistamines undergo hepatic metabolism; one of Vistaril's metabolites is cetirizine, a second-generation antihistamine. Cetirizine is excreted in urine.
  • Vistaril is a pamoate salt of hydroxyzine, while Atarax is a hydrochloride salt of hydroxyzine. This difference in preparations has no clinical significance.

References

1. Pau Celada, M. Victoria Puig, et.al. The therapeutic role of 5-HT1A and 5-HT2A receptors in depression J Psychiatry Neurosci. 2004 Jul; 29(4): 252–265.

2. Llorca PM; Spadone C; Sol O et al. Efficacy and safety of hydroxyzine in the treatment of generalized anxiety disorder: a 3-month double-blind study. J Clin Psychiatry 2002, 63 (11): 1020–7. doi:10.4088/JCP.v63n1112. PMID 12444816

3. Kubo N, Shirakawa O, Kuno T, et al. Antimuscarinic effects of antihistamines: quantitative evaluation by receptor-binding assay. Jpn J Pharmacol. 1987;43:277-282 </br>

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