11: Toxicity of Decongestants and Antihistamines Flashcards
congestion of nasal and sinus passageways is mainly caused by
vasodilation, vascular permeability, and edema
decongestants are ________ which act on __________
sympathomimetics
vascular smooth tissue
decongestant effects include
vasoconstriction
reduced blood flow
relief of congestion
potential for stimulating properties
topical decongestants class
imidazolines
list the 4 topical decongestants/ imidazolines
oxymetazoline
tetrahydrozoline
xylometazoline
nephazoline
list the 2 systemic decongestants sympathomimetics
pseudoephedrine
phenylephrine
what is the preferred type of decongestant when nasal congestion is the only sx
topical decongestant
which decongestant has slower onset and more SEs
systemic decongestants
AEs of topical decongestants
transient burning, stinging, dryness of nasal mucosa
caution in small children as ingestion of 1-2mL = coma, decr HR, breathing, sedation
rhinitis medicamentosa
AEs of systemic decongestants
CNS stimulation
Cardiovascular issues
peripheral vasoconstriction
adverse effect on blood sugar control in diabetics
rebound congestion is due to
prolonged use of topical decongestants (>3-5d)
rebound vasoconstriction is more common in _________ than ____________
shorter acting agents (phenylephrine) than longer acting (oxymetazoline, xylometazoline)
if a patient has rebound congestion, they may need to be titrated off topical decongestants with
nasal saline and steroids
how do decongestants affect the heart
tachycardia, dysrhythmias
cardiovascular SEs are more common with which decongestant? why?
pseudoephedrine
additive B1 agonist properties
peripheral vasoconstriction with decongestants is due to
peripheral a1 stimulation = release of NE
caution the use of decongestants in
1. diabetics
2. HPTN pts
3. hyperthyroidism
4. those on SSRIs
5. all of the above
6. 1, 2, 4
7. 1, 2, 3
7
decongestants should be avoided in pts on MAOis within _____s of taking them
2wks
why should you avoid decongestants in pts taking MAOis for 2 wks
MAOis inhibits breakdown of NE = more peripheral vasoconstriction and BP rise = hypertensive crisis
decongestant effect on blood sugar
pseudoephedrine increases blood sugars by increasing release of NE which causes breakdown of glycogen (glycogen lysis) to use as a source of energy
T or F: systemic absorption from topical formulations is low = AEs are mainly local only
T
Pseudoephedrine is ____ readily absorbed than phenylephrine = toxicity ____ likely
more
decongestants are mainly ____ eliminated
renally
clinical manifestations of imidazoline toxicity include
central depression
CNS depression
Hypertension to hypotension
Bradycardia
Respiratory depression
Sympathomimetic decongestants cause false-positive results for _______on several rapid__________
amphetamines
urine drug screens
Comprehensive ____________screening test by LC/MS or GC/MS can be obtained for research purposes or in forensic studies to determine the cause of death but = no role in immediate clinical management of poisoned pts
blood or urine analysis
T or F: there is a role for blood or urine analysis for decongestant use if treating pt that is overdosing at the hospital
F- research or forensics only
acute treatment of decongestant toxicity is based on
clinical sx
T or F: cardiac monitors should be used for decongestant toxicity patients to monitor for dysrhythmias
T
is charcoal ever used for GI decontamination in decongestasnt OD?
yes if large amounts of pseudoephedrine is ingested
are whole bowel irrigation and renal enhanced elimination techniques indicated for decongestant toxicity
no
Agitation, seizures, psychosis from decongestant toxicity may be treated with
IV BZDs
tachycardia and HPTN from mild decongestant toxicity may respond to
BZDs
persistent hypertension and chest pain from decongestant toxicity is best treated with
1. ACEi
2. nitrates
3. beta blockers
4. phentolamine
4
Persistent hypertension of chest pain after decongestant OD = indication of ____________
ischemic cardiomyopathy
how to tx ventricular dysrhythmias from decongestants
IV lidocaine
monitor for resolution of decongestant toxicity sx within____, _____ if SR used
8-16hrs
up to 24hrs if SR
No evidence to support use of decongestants or antihistamine/ decongestant combos in children _____, SR formulations not rec ______
<6yrs
<12yrs
how are decongestants abused
nonrx pseudoephedrine is used to make methamphetamines
antihistamines are ______- of the _____ receptor
inverse agonists
H1
antihistamine MOAs
Inhibit respiratory smooth muscle constriction
↓ capillary permeability = ↓ itch response
↓ histamine activated exocrine secretions (salivary, lacrimal)
1st gen antihistamine characteristics
less H1 receptor specificity, a adrenergic and cardiac ion channel SEs
more lipophilic= CNS effects
some 1st gen antihistamines had 2 additional effects
antiemetic
sleep aids
2nd gen antihistamine characteristics
Less off target effect = less potential toxicity
↓ lipophilic = ↓ drowsiness
what gen antihistamines are recommended in the elderly
2nd gen
CNS effects of antihistamines
sedation, dizziness, impaired cognition, psychomotor fxn
lower work performance
paradoxical excitation in children
caution use of antihistamines in patients with
angle closure glaucoma and CV diseases
which antihistamine is the most involved in peds exposures/ substance related deaths
diphenhydramine
antihistamines are metabolized by _________ and _____ excreted
hepatic metabolism
renally excreted
antihistamines Vd
large- difficult to remove once distributed
________ individuals have prolonged elimination/ t1/2 of diphenhydramine
Elderly i
cardiovascular SEs from antihistamines include
QRS complex and QT interval prolongation due to effect on cardiac Ca+ channels
hypotention, dizziness
sinus tachycardia
diphenhydramine causes false +s on
methadone
phencyclidine
TCAs
how to manage seizures from antihistamine toxcixity? what about refractory
IV BZDs
propofol for refractory
T or F: phenytoin is recommended for antihistamine induced seizures
F
how to treat anticholinergic SEs from antihistamines? what about cholinergic toxicity
physostigmine
IV stropine for cholinergic toxicity
how to treat cardiac arrhythmias from antihistamines
hypertonic sodium bicarbonate
in most patients, antihistamine toxicity are acutely sx for ______ and ____ manifestaions resolve before _______ sx
24-48hrs
cardiac before CNS
diphenhydraine may be abused for
anxioltycia dn euphoric effects
