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pre reg afsha > Nausea and Labyrinth Disorders > Flashcards

Nausea and Labyrinth Disorders Flashcards

1
Q

Causes of nausea and labyrinth disorders

A
  • Drugs and toxic substances
  • Labyrinthitis (inner ear infections)
  • Vestibular disorders
  • Motion sickness
  • Gut irritation
  • Higher stimuli (sights, smells, emotions)
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1
Q

Why does n+v occur

A
  • Occurs when vomiting centre in brain is activated by input from the chemoreceptor trigger zone (CTZ)
  • CTZ is located in the medulla oblongata of the brainstem and contains dopamine, serotonin, histamine and muscarinic receptors
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2
Q

When should antiemetics be prescribed

A

Generally only when cause of vomiting is known - otherwise, they may delay diagnosis, esp in children
If indicated, drug chosen according to aetiology

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3
Q

How do antiemetics work

A

Antagonising the receptors in the CTZ

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4
Q

What is metoclopramide

A
  • Dopamine antagonist
  • Antagonises D2 receptors in CTZ
  • Acts directly on gastric smooth muscle, stimulating gastric emptying - prokinetic effect
  • Has antiemetic properties
  • Activity closely resembles phenothiazines, but because it is pro kinetic, it may be superior for emesis associated with GI and biliary disease
  • Useful in gastroduodenal, hepatic and biliary disease
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5
Q

What is domperidone

A
  • Dopamine antagonist
  • Acts at CRZ - antagonises D2 receptor
  • Advantages over metoclopramide and phenothiazines: less likely to cause central effects (e.g. sedation, dystonic reactions) as it does not cross BBB
  • Acts directly on gut to promote gastric emptying - pro kinetic
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6
Q

Antiemetic of choice in Parkinson’s disease

A
  • Domperidone
  • Low doses can be used to treat nausea caused by dopaminergic drugs
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7
Q

Antiemetics to avoid in Parkinsons disease

A

Metoclopramide, haloperidol, prochlorperazine.
These medicines have a very high risk of worsening PD symptoms as they block D2 receptors.

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8
Q

Antipsychotics with antiemetic properties

A
  • Prochlorperazine: buccal tablets used in n+v for migraine and for post-op
  • Perphenazine, trifluoperazine, chlorpromazine: used post-op
  • Droperidol: used post-op
  • Haloperidol (unlicensed) and levomepromazine: used in palliative care to relieve n+v
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9
Q

Antihistamines with antiemetic properties

A

○ For vertigo, cinnarizine, cyclizine, promethazine teoclate
○ For vertigo + motion sickness, the above + hyoscine hydrobromide
○ HH is most effective in motion sickness
○ Duration of action and incidence of SE, e.g. drowsiness and antimuscarinic effects, differs between antihistamine

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10
Q

Hyoscine: which one is most effective in preventing motion sickness

A

HH - hyoscine hydrobromide

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11
Q

5HT3 receptor antagonist antiemetics

A

○ For chemotherapy or post op n+v:
Granisetron
Ondansetron
Palonosetron
○ Combination of palonosetron with netupitant (neurokinin 1 receptor antagonist) also available

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12
Q

What are thenothiazines

A

○ Chlorpromazine HCl, prochlorperazine, trifluoperazine
○ Dopamine antagonists that act centrally by blocking CRZ
○ Severe dystonic reactions sometimes occur, (cross BBB) esp in children
○ Prochlorperazine can be used for chemo-induced and radiation-induced n/v
○ Less sedating
○ Available as buccal tablet - useful in pt with persistent vomiting or severe nausea

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13
Q

Can dexamethasone be used as antiemetic

A

Yes
Usually for cancer chemotherapy and post-op
Can be used alone or in combination with other antiemetics

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14
Q

What is nabilone

A

Synergic canabinoid
Used in chemo unresponsive to other anti emetics
Can be considered as add-on treatment for chemotherapy induced n+v unresponsive to optimised conventional antiemetics

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15
Q

What are the NK1R antagonists

A
  • Aprepitant, fosprepitant, rolapitant
  • Used to prevent chemo associated n+v, usually given with dexa + 5HT3 antagonist
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16
Q

How long do women usually experience n+v for in pregnancy

A
  • Common in 1st trimester
  • Usually resolves spontaneously within 16-20 weeks
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17
Q

Self care advise for n+v in pregnancy

A

Rest
Oral hydration
Dietary changes
Advise on when to seek urgent medical advice

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18
Q

When should antiemetics be considered for pregnant women with n+v

A

Persistent symptoms and self care measures ineffective

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19
Q

Non pharmacological option for pregnant women with n+v

A

Ginger for mild to moderate nausea

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20
Q

Antiemetic options for pregnancy

A

Chlorpromazine HCl
Cyclizine
Doxylamine + pyroxidine (Xonvea)
Metoclopramide
Prochlorperazine HCl
Promethazine HCl or teoclate
Ondansetron

21
Q

Monitoring when using antiemetics in pregnancy

A
  • Assess response to treatment after 24 hours, if the response is inadequate, switch to an antiemetic from a different class
    Reassess after 24h and if symptoms not settles, specialist option
22
Q

Moderate to severe n+v

A

Consider IV fluids and adjunct treatment with acupressure

23
Q

Hyperemesis gravidarium

A
  • Excessive and prolonged n+v
  • More serious
  • Requires regular antiemetics, IV fluid and electrolyte replacement
  • Sometimes will need nutritional support - can’t keep food and drink down
  • For women with severe or persistent HG, may be more suitable to give parenteral or rectal antiemetics
  • Consider thiamine supplementation to reduce risk of Wernick’s encephalopathy
24
Q

Risk factors for post op n+v

A

○ Type anaesthesia used
○ Type and duration of surgery
○ Females
○ Younger age
○ Non smokers
○ PHx of PONV or motion sickness
○ Motion sickness
○ Opioid use

25
Q

What to do when prophylactic antiemetic for PONV fails

A

Treat PONV with antiemetic drug from a different therapeutic class

26
Q

Antiemetic prevention in PONV examples

A
  • 5HT3 receptor antagonist (-setron), droperidol, haloperidol, dexamethasone
  • Cyclizine (antihistamine) licensed for prevention and treatment of PONV caused by opioids and GA
  • Phenothiazine antipsychotic: prochlorperazine licensed for prevention and treatment of n+v
27
Q

Treatment of patients with risk of PONV (patients with risk factors)

A

Combination of 2 or more antiemetics from different drug classes

28
Q

Motion sickness - when to take treatment

A

Antiemetics should be used to PREVENT motion sickness, rather than to be taken after n+v develop

29
Q

Which drug are ineffective in motion sickness so should not be given

A

Domperidone
Metoclopramide
5HT3 receptor antagonists (-setron)
Phenothiazines (except the antihistamine phenothiazine promethazine)

30
Q

Drugs that can be used to prevent motion sickness

A

Hyoscine hydrobromide: licensed ti prevent motion sickness symptoms e.g. n+v, vertigo
Antihistamine drugs may also be effective - less sedating ones include cinnarizine, cyclizine whereas more sedating ones include promethazine HCl + teoclate

31
Q

MHRA advice on use of metoclopramide

A
  • Risk of neurological SE e.g. extra-pyramidal effects
  • Restrictions to indications, dose and duration
  • Indications: prevention of PONV, radiotherapy induced or delayed chemo induced NV, symptomatic treatment of NV e.g. acute migraine, also to improve absorption of oral analgesics
  • Short term use - max 5 days
  • For 18+, max 5 days, 10mg TDS, max 500mcg/kg
  • Does not apply to unlicensed use (e.g. palliative care)
32
Q

SE of metoclopramide includes .. and which drug can counteract these effects

A
  • Acute dystonic reactions: facial and skeletal muscle spasms, oculogyric crises
  • More common in young (esp girls and young females) and the very old
  • Procyclidine (anti-Parkinsonian drug) aborts dystonic attacks
33
Q

Interactions of metoclopramide

A
  • AVOID in PD - exacerbates condition
  • Antipsychotics - increased extrapyramidal SE
34
Q

MHRA advice on use of domperidone

A
  • Risk of cardiac SE
  • Restriction indicated: symptomatic relief of n+v, choice of antiemetic in PD as does not cause extrapyramidal SE
  • Contraindicated in impaired cardiac conditions, cardiac disease & severe liver impairment
  • Max use: 1 week, 10mg TDS, adult/12+ and over 35kg
  • For children under 35kg, max use is 250cmg/kg TDS
  • Cardiac SE include: QT prolonged, ventricular arrhythmias, sudden death
  • Counsel pt to report sign of arrhythmias: syncope, palpitations
35
Q

Domperidone interactions

A

Potent CYP34A inhibitors e.g. amiodarone, ketoconazole, erythromycin
Drugs causing QT prolongation e.g. amiodarone, SSRIs, quinolone

36
Q

5HT3 receptor antagonists - how do they work

A
  • Block 5HT3R in CRZ and GIT
  • 5HT is a key NT released by gut in response to emetogenic stimuli
37
Q

Indications for granisetron, ondansetron

A

PONV
Chemotherapy-induced n,v

38
Q

Indications for palonosetron

A

Prevention of n/v associated with moderately or highly emetogenic cytotoxic chemotherapy

39
Q

SE of 5HT3 RAnt

A

QT interval prolongation

40
Q

Interactions: 5HT3 RAnt

A

Increased risk of torsade de pointes with HYPOkalaemia - loop/thiazide diuretics, CCs, beta-agonists (e.g. salbutamol), theophylline, stimulant laxative abuse, amphotericin B

Increases risk of QT interval prolongation - amiodarone, clarithromycin, quinine, sumatriptan, lithium, antipsychotics

Serotonin syndrome - SSRIs, MAOIs, 5HT1A agonist (e.g. triptans)

41
Q

What is mernier’s disease & what are the symptoms

A
  • Rare disorder that affects inner ear
  • Can affect balance and hearing
  • Can cause vertigo (spinning sensation), losing balance, feeling sick, tinnitus (ringing in ears), hearing loss, feeling of pressure in ear
42
Q

What to do if pt presents with symptoms of Mernier’s disease

A
  • Refer to ENT specialist to confirm diagnosis
43
Q

Is there a cure to Mernier’s disease? What treatments are given?

A

No
Treatments include medication to prevent dizziness and n+v

44
Q

Drugs used to alleviate n+v and vertigo in acute attacks of Mernier’s

A

○ Antihistamines
Cinnarizine
Cyclizine
Promethazine teoclate
○ Phenothiazines
Prochlorperazine

45
Q

Drugs used to rapidly relieve n+v in severe acute attacks of Mernier’s

A

○ Buccal promethazine
○ Deep IM injection of prochlorperazine or cyclizine

46
Q

What is betahistine and what is it used for and the dose

A

○ Analogue of histamine
○ Can be trialled to reduce freq and severity of hearing loss, tinnitus and vertigo in pt with recurrent attacks
○ Dose, adult, PO: initially 16mg TDS, dose pref taken with food
○ Maintenance dose 24-48mg daily

47
Q

Contraindications and cautions - betahistine

A

Contradicted in phaeochromocytoma
Cautions: asthma, history of peptic ulcer

48
Q

Common or very common SE

A

GI discomfort
Headache
Nausea

49
Q
A
50
Q
A

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