Preparation for Child Psych PRITE and Boards
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==Diphenhydramine (Benadryl) == | ==Diphenhydramine (Benadryl) == | ||
| − | * Benadryl is a first-generation antihistamine; in addition to blocking H-1 receptors, it is a potent anti-cholinergic drug 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 | + | * 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) | ** 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 for | + | * 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. | + | * Benadryl is '''generally safe in pregnancy''' (Category B), but is excreted in breast milk. |
| − | * It can prolong QTc 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''' | ||
| − | ==Hydroxyzine (Vistaril, Atarax) | + | ==Hydroxyzine (Vistaril, Atarax) == |
| + | *Vistaril is another first generation antihistamine commonly used in psychiatry. It is just as sedating as Benadryl, but has weaker 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 psychaitry for sleep and as PRN in behavioral emergencies. Unfortunately it is not available in intramuscular (IM) form. | ||
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| + | == 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. | ||
| + | ** This also means that Benadryl can contribute to a serotonin toxicity, particularly when combined with other serotonergic drugs. | ||
| + | * Vystaril acts on 5-HT2a receptor which justifies its clinical use in generalized anxiety disorder. | ||
| + | * Most antihistamines undergo hepatic metabolism; one of Vistaril's metabolites is '''ceterizine''', a 2nd generation antihistamine. Ceterizine is excreted in urine. | ||
[[Category: Medications]] | [[Category: Medications]] | ||
Revision as of 15:39, 25 April 2015
Contents
Introduction
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 inverse agonism of the central H-1 receptor increases sedation.
- Second-generation antihistamines do not cross the blood-brain barrier, and thus are less sedating.
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, but has weaker 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 psychaitry for sleep and as PRN in behavioral emergencies. Unfortunately it is not available in intramuscular (IM) form.
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.
- This also means that Benadryl can contribute to a serotonin toxicity, particularly when combined with other serotonergic drugs.
- Vystaril acts on 5-HT2a receptor which justifies its clinical use in generalized anxiety disorder.
- Most antihistamines undergo hepatic metabolism; one of Vistaril's metabolites is ceterizine, a 2nd generation antihistamine. Ceterizine is excreted in urine.