11: Toxicity of Decongestants and Antihistamines

Question 1

congestion of nasal and sinus passageways is mainly caused by

Answer 1

vasodilation, vascular permeability, and edema

Question 2

decongestants are ________ which act on __________

Answer 2

sympathomimetics
vascular smooth tissue

Question 3

decongestant effects include

Answer 3

vasoconstriction
reduced blood flow
relief of congestion
potential for stimulating properties

Question 4

topical decongestants class

Answer 4

imidazolines

Question 5

list the 4 topical decongestants/ imidazolines

Answer 5

oxymetazoline
tetrahydrozoline
xylometazoline
nephazoline

Question 6

list the 2 systemic decongestants sympathomimetics

Answer 6

pseudoephedrine
phenylephrine

Question 7

what is the preferred type of decongestant when nasal congestion is the only sx

Answer 7

topical decongestant

Question 8

which decongestant has slower onset and more SEs

Answer 8

systemic decongestants

Question 9

AEs of topical decongestants

Answer 9

transient burning, stinging, dryness of nasal mucosa
caution in small children as ingestion of 1-2mL = coma, decr HR, breathing, sedation
rhinitis medicamentosa

Question 10

AEs of systemic decongestants

Answer 10

CNS stimulation
Cardiovascular issues
peripheral vasoconstriction
adverse effect on blood sugar control in diabetics

Question 11

rebound congestion is due to

Answer 11

prolonged use of topical decongestants (>3-5d)

Question 12

rebound vasoconstriction is more common in _________ than ____________

Answer 12

shorter acting agents (phenylephrine) than longer acting (oxymetazoline, xylometazoline)

Question 13

if a patient has rebound congestion, they may need to be titrated off topical decongestants with

Answer 13

nasal saline and steroids

Question 14

how do decongestants affect the heart

Answer 14

tachycardia, dysrhythmias

Question 15

cardiovascular SEs are more common with which decongestant? why?

Answer 15

pseudoephedrine
additive B1 agonist properties

Question 16

peripheral vasoconstriction with decongestants is due to

Answer 16

peripheral a1 stimulation = release of NE

Question 17

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

Answer 17

7

Question 18

decongestants should be avoided in pts on MAOis within _____s of taking them

Answer 18

2wks

Question 19

why should you avoid decongestants in pts taking MAOis for 2 wks

Answer 19

MAOis inhibits breakdown of NE = more peripheral vasoconstriction and BP rise = hypertensive crisis

Question 20

decongestant effect on blood sugar

Answer 20

pseudoephedrine increases blood sugars by increasing release of NE which causes breakdown of glycogen (glycogen lysis) to use as a source of energy

Question 21

T or F: systemic absorption from topical formulations is low = AEs are mainly local only

Answer 21

T

Question 22

Pseudoephedrine is ____ readily absorbed than phenylephrine = toxicity ____ likely

Answer 22

more

Question 23

decongestants are mainly ____ eliminated

Answer 23

renally

Question 24

clinical manifestations of imidazoline toxicity include

Answer 24

central depression
CNS depression
Hypertension to hypotension
Bradycardia
Respiratory depression

Question 25

Sympathomimetic decongestants cause false-positive results for _______on several rapid__________

Answer 25

amphetamines urine drug screens

Question 26

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

Answer 26

blood or urine analysis

Question 27

T or F: there is a role for blood or urine analysis for decongestant use if treating pt that is overdosing at the hospital

Answer 27

F- research or forensics only

Question 28

acute treatment of decongestant toxicity is based on

Answer 28

clinical sx

Question 29

T or F: cardiac monitors should be used for decongestant toxicity patients to monitor for dysrhythmias

Answer 29

T

Question 30

is charcoal ever used for GI decontamination in decongestasnt OD?

Answer 30

yes if large amounts of pseudoephedrine is ingested

Question 31

are whole bowel irrigation and renal enhanced elimination techniques indicated for decongestant toxicity

Answer 31

no

Question 32

Agitation, seizures, psychosis from decongestant toxicity may be treated with

Answer 32

IV BZDs

Question 33

tachycardia and HPTN from mild decongestant toxicity may respond to

Answer 33

BZDs

Question 34

persistent hypertension and chest pain from decongestant toxicity is best treated with 1. ACEi 2. nitrates 3. beta blockers 4. phentolamine

Answer 34

4

Question 35

Persistent hypertension of chest pain after decongestant OD = indication of ____________

Answer 35

ischemic cardiomyopathy

Question 36

how to tx ventricular dysrhythmias from decongestants

Answer 36

IV lidocaine

Question 37

monitor for resolution of decongestant toxicity sx within____, _____ if SR used

Answer 37

8-16hrs up to 24hrs if SR

Question 38

No evidence to support use of decongestants or antihistamine/ decongestant combos in children _____, SR formulations not rec ______

Answer 38

<6yrs <12yrs

Question 39

how are decongestants abused

Answer 39

nonrx pseudoephedrine is used to make methamphetamines

Question 40

antihistamines are ______- of the _____ receptor

Answer 40

inverse agonists H1

Question 41

antihistamine MOAs

Answer 41

Inhibit respiratory smooth muscle constriction ↓ capillary permeability = ↓ itch response ↓ histamine activated exocrine secretions (salivary, lacrimal)

Question 42

1st gen antihistamine characteristics

Answer 42

less H1 receptor specificity, a adrenergic and cardiac ion channel SEs more lipophilic= CNS effects

Question 43

some 1st gen antihistamines had 2 additional effects

Answer 43

antiemetic sleep aids

Question 44

2nd gen antihistamine characteristics

Answer 44

Less off target effect = less potential toxicity ↓ lipophilic = ↓ drowsiness

Question 45

what gen antihistamines are recommended in the elderly

Answer 45

2nd gen

Question 46

CNS effects of antihistamines

Answer 46

sedation, dizziness, impaired cognition, psychomotor fxn lower work performance paradoxical excitation in children

Question 47

caution use of antihistamines in patients with

Answer 47

angle closure glaucoma and CV diseases

Question 48

which antihistamine is the most involved in peds exposures/ substance related deaths

Answer 48

diphenhydramine

Question 49

antihistamines are metabolized by _________ and _____ excreted

Answer 49

hepatic metabolism renally excreted

Question 50

antihistamines Vd

Answer 50

large- difficult to remove once distributed

Question 51

________ individuals have prolonged elimination/ t1/2 of diphenhydramine

Answer 51

Elderly i

Question 52

cardiovascular SEs from antihistamines include

Answer 52

QRS complex and QT interval prolongation due to effect on cardiac Ca+ channels hypotention, dizziness sinus tachycardia

Question 53

diphenhydramine causes false +s on

Answer 53

methadone phencyclidine TCAs

Question 54

how to manage seizures from antihistamine toxcixity? what about refractory

Answer 54

IV BZDs propofol for refractory

Question 55

T or F: phenytoin is recommended for antihistamine induced seizures

Answer 55

F

Question 56

how to treat anticholinergic SEs from antihistamines? what about cholinergic toxicity

Answer 56

physostigmine IV stropine for cholinergic toxicity

Question 57

how to treat cardiac arrhythmias from antihistamines

Answer 57

hypertonic sodium bicarbonate

Question 58

in most patients, antihistamine toxicity are acutely sx for ______ and ____ manifestaions resolve before _______ sx

Answer 58

24-48hrs cardiac before CNS

Question 59

diphenhydraine may be abused for

Answer 59

anxioltycia dn euphoric effects