39. Uterotonics Flashcards
OXYTOCIN
Trade name: Syntocinon
Synthetically produced posterior pituitary hormone
• Clear colourless solution:
5 IU/mL
DOSE
• Induction of labour by IV infusion 0.001–0.002 u/min.
Do not exceed 5 u per day
• 5 u by slow bolus given immediately following
delivery of newborn at caesarean section
MOA
• Stimulates uterine contraction by binding to
specific sites on muscle cells
• Agonist at oxytocin receptor G protein
coupled receptor
• To cause uterine contraction: • Induction of labour • Following caesarean section • Following abortion
CHEMICAL PROPERTIES
• Octapeptide
OXYTOCIN
ADME
METABOLISM AND EXCRETION
• Hepatic and renal metabolism
ABSORPTION/DISTRIBUTION
- Given IV
- Acts within 2–3 min
EFFECTS
GU
• Uterine contraction. Fetal heart rate must be
monitored once infusion starts
• Overdose can cause hyperstimulation
• Mild antidiurectic effect, only apparent with
prolonged use
CVS
- ↑ SVR
- ↑ BP
• Severe hypertension in patients with cardiac
disease
• Tachycardia (marked) follows bolus –
give slowly
GI
• Nausea and vomiting
Other
- Rash
- Anaphylaxis
- Amniotic fluid embolism reported following overdose
CARBETOCIN
CARBETOCIN
Long acting synthetic analogue of oxytocin
Clear colourless solution
100 ug/mL
• 100 μg IV over 1 min given immediately
following parturition.
• Once only dosing
• Uterine contractionsustained for approx.
1 hour (compared to syntocinon = approx.
15 mins)
MOA
• Agonist at G protein coupled oxytocin
receptor and so stimulates uterine
contraction.
• Effects seen within 2 mins, last 1 hour.
USES • To cause sustained uterine contraction following caesarean section.
• Can only give 1 dose
CHEMICAL
PROPERTIES
• None
Carbetocin
CARBETOCIN
METABOLISM &
EXCRETION
• Mechanism of elimination not known
? enzymatic degradation
• Minimally renally excreted (0.7%)
ABSORPTION/
DISTRIBUTION
• t½ 85 – 100 mins
EFFECTS
CVS
• Tachycardia
Chest pain
RS
• Respiratory distress
CNS
• Dizziness
• Metallic taste
GI
• N&V
• Abdo pain
OTHER • Itching • Raised temp • Sweating • Chills • Trembling • Back pain
CAUTION IN THOSE WITH UTEROTONICS
• Hypertension
• IHD
ERGOMETRINE
Ergot alkaloid derivative
- Solution: 0.5 mg/mL
- Tablets: 0.5 mg
• Combined with syntocinon (syntometrine):
0.5 mg ergometrine + 5 IU
syntocinon/mL for IM injection
DOSE
• 0.5 mg IM or 0.125 mg by slow IV injection.
Repeat if necessary
MOA
• Stimulates uterine and vascular smooth muscle
contraction? by binding to 5HT receptors
• Stimulates D2 receptors at chemoreceptor trigger zone (CTZ) causing emesis
USES
• To cause uterine contraction and reduce
bleeding:
1 Following caesarean section
2 Second line treatment of uterine atony
after oxytocin / carbetocin
3 Following abortion
ERGOMETRINE
ADME
ABSORPTION/
DISTRIBUTION
• Acts within
- 1 min IV
- 5 min IM
- 10 min PO
- Lasts 3–6 hours
METABOLISM
AND EXCRETION
• Hepatic metabolism
• Excreted in bile
ERGOMETRINE
Effectys
EFFECTS GU • Uterine contraction follows 1 min after IV and 5 min after IM dosing
CVS
• ↑ SVR and BP
• Severe hypertension.
Can be harmful in patients
with cardiac disease –
lasts several hours
- CI in pre-eclampsia
- Bradycardia and arrhythmias (marked)
- MI reported
- Pulmonary oedema
CNS
• Headache
- Dizziness
- Tinnitus
- CVA reported
GI
• Severe nausea and vomiting
CARBOPROST
Prostaglandin F2a analogue
Trade name: Hemabate
• Solution: 250 μg/mL
DOSE
• 250 μg IM or directly into uterine muscle.
Repeat every 15 min as necessary
• Max dose 2 g
MOA
• Stimulates uterine contraction
• Mechanism not elucidated
USES
• To cause uterine contraction and stop
post-partum haemorrhage in patients
unresponsive to oxytocin and ergometrine
ADME
No INFO
CARBOPROST
EFFECTS
GU
• Uterine contraction
RS
• Bronchospasm – relatively contraindicated in
asthmatics
CVS
- Cardiovascular collapse reported
- Pulmonary oedema (rare)
- Sweating
- Flushing
CNS
• Headache
• Dizziness
GI
• Nausea and vomiting
