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DIG F > F6 Nausea, vomiting and electrolyte balance > Flashcards

F6 Nausea, vomiting and electrolyte balance Flashcards

1
Q

uses of histamine H1 receptor antagonists

A
  • motion sickness
  • morning sickness of pregnancy
  • space motion sickness (by NASA)
  • antimuscarinic actions
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2
Q

what do histamine H1 receptor antagonists cause?

A
  • drowsiness and sedation
  • should not drive if taking
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3
Q

what do histamine H1 receptor antagonists do?

A

block the histamine H1 receptor

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4
Q

give an example of a histamine H1 receptor antagonist

A

promethazine

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5
Q

uses of muscarinic M1 receptor antagonists

A
  • prophylaxis and treatment of motion sickness
  • reduce gastric motility
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6
Q

what side effects do muscarinic M1 receptor antagonists have?

A
  • antmuscarinic side effects
  • eg. dry mouth
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7
Q

what effect can muscarinic M1 receptor antagonists produce?

A
  • drowsiness
  • (less sedation)
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8
Q

give an example of a muscarinic M1 receptor antagonist

A
  • eg. hyoscine
  • eg. Kwells
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9
Q

where do dopamine D2 receptor antagonists act? what unwanted effects do they have?

A
  • act in CTZ
  • have unwanted CNS effects
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10
Q

what are dopamine D2 receptor antagonists effective for?

A
  • anti-cancer drug effects of vomiting (chemotherapy induced emesis)
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11
Q

what is the D2 receptor involved in?

A

movement

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12
Q

what can dopamine D2 receptor antagonists cause and how?

A
  • Parkinsonian syndrome
  • antagonism of D2 receptors leads to Parkinson’s-like symptoms
  • decline of dopamine in Parkinson’s so medications that block D2 receptors reproduce effects through side effects
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13
Q

give an example of a side effect that may be seen with dopamine D2 receptor antagonists

A
  • muscle dystonias (symptom of Parkinsonian syndrome)
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14
Q

state a contraindication of dopamine D2 receptor antagonists

A

Parkinson’s

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15
Q

what else can dopamine D2 receptor antagonists stimulate other than stopping vomiting?

A

stimulates gastric emptying and reduce nausea

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16
Q

how are dopamine D2 receptor antagonists useful in migraines?

A
  • they have pro kinetic effects (increase gastric emptying rate)
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17
Q

state 2 examples of dopamine D2 receptor antagonists

A
  • metoclopramide
  • domperidone
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18
Q

what type of drug is prochlorperazine?

A

D2 receptor antagonist
AND
muscarinic receptor antagonist

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19
Q

what does metoclopramide block?

A
  • apomorphine-induced vomiting
  • can produce muscle dystonia and Parkinsonian syndrome
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20
Q

what do 5-hydroxytryptamine (5-HT) receptor antagonists do?

A
  • block 5-HT at 5-HT3 receptors in gut and CNS
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21
Q

what are 5-hydroxytryptamine (5-HT) receptor antagonists particularly effective against?

A

chemotherapy-induced emesis

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22
Q

are 5-hydroxytryptamine (5-HT) receptor antagonists effective for motion sickness?

A

no

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23
Q

why are 5-hydroxytryptamine (5-HT) receptor antagonists not effective for motion sickness?

A

in motion sickness, the neurotransmitters are either histamine or acetylcholine

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24
Q

give an example of 5-hydroxytryptamine (5-HT) receptor antagonists

A

ondansetron

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25
what is the NK1 receptor activated by?
substance P
26
what do neurokinin NK1 receptor antagonists suppress?
nausea and vomiting
27
when are neurokinin NK1 receptor antagonists used and how?
- used in chemotherapy-induced nausea and vomiting - used in combination with 5-HT receptor antagonist
28
state an example of a neurokinin NK1 receptor antagonist
aprepitant
29
when are steroids used in relation to vomiting and how do they work?
- used in chemotherapy-induced nausea and vomiting - mechanism is unknown
30
give an example of a steroid used to suppress vomiting
dexamethasone
31
describe and explain the general prescribing regimen for chemotherapy-induced nausea and vomiting
- prescribe a combo of antiemetics to reduce prevalence of nausea and vomiting in cancer patients - should be a combo that will get max patient compliance - synergism is desirable
32
give an example of a combo of drugs that could be given to reduce nausea and vomiting in cancer patients
- 5-HT3 antagonist - steroid - NK1 antagonist
33
what is the dosing for a 5-HT3 antagonist given to cancer patients to reduce nausea and vomiting?
- 8mg 1 hour before treatment - 8mg every 12 hours for up to 5 days
34
what is the dosing for a NK1 antagonist given to cancer patients to reduce nausea and vomiting?
- 125mg 1 hour before treatment - 80mg daily for next 2 days
35
what does vomiting cause a loss of?
H+ K+ H2O
36
consequences of losses in H+, K+ and H2O due to vomiting
- acid / base imbalance - electrolyte imbalance - impaired nerve and muscle function
37
what is the name for acid / base imbalance?
metabolic alkalosis
38
what can diarrhoea cause the loss of? what do these losses cause?
Na+ H2O results in dehydration
39
consequences of losses of Na+ and H2O due to diarrhoea
- reduction in blood pressure (fluid loss) - muscle weakness / cramps - reduced level of consciousness - heart failure - convulsions
40
state 3 symptoms of diabetes relating to urine
polyurea (weeing lots) polydipsia (thirst) polyphagia (hunger)
41
what must be replenished after excessive vomiting?
- water - electrolytes
42
what can changes in electrolyte balance across membranes cause?
- effects on nerve impulses and condition of electrical impulses across heart - can result in irregular heart rate
43
what can low Na+ cause?
lethargy, seizures and respiratory problems
44
what can the swelling and shrinking of cells do to the body?
- can have major effects on the body - need to balance electrolyte concentrations across cell membranes
45
where is sodium mainly concentrated?
in the extracellular fluid
46
what is the most abundant extracellular cation?
Na+
47
what does the osmotic activity of extracellular fluid depend on?
relative proportion of Na+ and H2O
48
what is Na+ and H2O excretion regulated by and where does it occur?
- excretion in kidney - regulated by the hormones vasopressin and aldosterone
49
what is hyponatraemia caused by?
- fluid retention / accumulation (eg. renal failure, heart failure) - MDMA abuse
50
how can MDMA abuse cause hyponatraemia?
- causes thought of needing to drink more water - MDMA stimulates vasopressin secretion and water retention
51
what does hyponatraemia lead to? state the order of events
- water movement into cells - cells swell - cerebral oedema - pressure on brain - nausea and vomiting, convulsions, headaches - coma - death
52
treatment for hyponatraemia
- H2O restriction - increase salt intake
53
what causes hypernatraemia?
- decrease in H2O - diabetes: increases urination and water loss
54
why is hypernatraemia due to a decrease in H2O rare?
thirst stimulates drinking urge (protective physiological mechanism)
55
what does hypernatraemia lead to? list order of events
- water moves out of cells - decrease in cell volume - decrease in brain size - coma
56
where is K+ mostly located?
inside cells
57
what can hyperkalaemia cause?
- muscle weakness - ECG changes - arrhythmias
58
what are arrhythmias?
changes in heartbeat that can be fatal
59
why can hyperkalaemia result in muscle weakness?
muscles rely on potassium for normal functioning
60
what does hypokalaemia result in?
- muscle weakness - ECG changes
61
what does a lower pH lead to regarding potassium ions?
- lower pH (acidosis) - H+ into cells - K+ out of cells
62
what does a higher pH lead to regarding potassium ions?
- higher pH (alkalosis) - increases entry of K+ into cells
63
when can potassium changes be fatal?
if affecting ventricular conductivity of the heart
64
main causes of hypokalaemia
- decreased intake - alkalosis - increased losses (vomiting, urine) - impaired renal function
65
main causes of hyperkalaemia
- decreased excretion (renal failure) - acidosis - medications like ACEi
66
when are ACEi medications especially likely to cause hyperkalaemia?
when used with K+ supplements
67
give an example of an ACEi that could cause hyperkalaemia
enalapril

DIG F (8 decks)

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