ENT Pharmacology

Question 1

Route of administration

Antihistamines
E.g.:
-Meclizine
-Dimenhydrinate
-Diphenhydramine

Answer 1

Oral (usually every
4-8 hours)
-Dimenhydrinate
can also be given
IV, IM, suppository)

Question 2

Antihistamines

Answer 2

E.g.:
-Meclizine
-Dimenhydrinate
-Diphenhydramine

Question 3

Indication Antihistamines

Answer 3

Acute motion sickness and
vertigo (see above notes)

Question 4

MOA of antihistamines

Answer 4

Histaminergic neurotransmission via
central H1 receptors involved in the link between neural mismatch signal and the emetic centre of brain.

Antihistamines will
reduce the neural mismatch signals
underlying motion sickness and vertigo

Question 5

Adverse effects of antihistamine

Answer 5

Drowsiness

-Sedation
(meclizine is less
sedating so may
be the better
option)

Question 6

EG of Anticholinergics

Answer 6

E.g.:
-Scopolamine

Question 7

Route of administration

Anticholinergics
E.g.:
-Scopolamine

Answer 7

Oral (usually every
4-8 hours)
-Transdermal patch
(effectiveness up to
3 days per patch)

Question 8

Indication Anticholinergics

Answer 8

-Acute motion sickness and
vertigo (see above notes)

Question 9

MOA of Anticholinergics

Answer 9

-Like the histaminergic pathways,
cholinergic neurotransmission is involved in pathways underlying sensory inputs and brain emetic centre. Blocking these pathways may reduce the neural mismatch signals underlying motion sickness and vertigo

Question 10

AE of anticholinergics

Answer 10

Drowsiness

-Sedation

-Dry mouth, dilated
pupils and other
anticholinergic
effects

Question 11

Route of administration

Benzodiazepines
E.g.:
-Diazepam
-Lorazepam

Answer 11

Oral
-IV

Question 12

Eg of Benzodiazepines

Answer 12

Diazepam
-Lorazepam

Question 13

indication of Benzodiazepines

Answer 13

Acute motion sickness and
vertigo (see above notes)

-Relieves anxiety related to
vertigo

Question 14

MOA of benziodiazepines

Answer 14

-Benzodiazepines such as diazepam act as positive allosteric modulators of inhibitory GABA-A receptors ->

reduces neurotransmission in pathways underlying
neural mismatch

Question 15

AE of benziodiazepines (8)

Answer 15

Ataxia, euphoria,
Incoordination,
somnolence,
hypotension,
headache,
dizziness, blurred
vision

Question 16

Why are non-sedating antihistamines such as fexofenadine not effective in treating motion sickness / vertigo?

Answer 16

Non-sedating antihistamines like fexofenadine are not effective in treating motion sickness or vertigo because they primarily target peripheral H1 receptors and do not adequately cross the blood-brain barrier. Motion sickness and vertigo are often mediated by central mechanisms in the brain, particularly involving the vestibular system and central H1 receptors.

In contrast, first-generation antihistamines (like diphenhydramine or dimenhydrinate) are effective for these conditions because they can cross the blood-brain barrier and have sedative properties, which help to reduce the central nervous system’s response to conflicting sensory signals that cause motion sickness. Essentially, non-sedating antihistamines lack the necessary central action to alleviate symptoms related to motion sickness and vertigo.