labetalol
Table of Contents
labetalol
see also beta blockers
Introduction:
- Racemic mixture of 4 isomers (beta-block 5 x alpha1-block):
- RR: beta-block 4 x racemic; alpha1-block 20% of racemic; intrinsic beta2 agonist
- RS: almost devoid blocker effects;
- SR: almost no beta-block; alpha1-block 5 x racemic;
- SS: almost no beta-block; alpha1-block approx racemic;
- ⇒ anti-HT,
- ⇒ arteriolar relaxation & vasodilation esp. in upright posture (alpha1-block);
- ⇒ vasodilation (beta 2 agonist);
- NB. also cocaine-like effect (decr. NA uptake);
- Labetalol is acceptable to use in breastfeeding
Indications
- Acute, severe hypertension during pregnancy or the post partum period
Contra-indications
- Severe or uncontrolled asthma
- Uncontrolled congestive cardiac failure
- History of allergic disorders with a predisposition to bronchospasm
- Second or third degree AV block
- Sick sinus syndrome (without pacemaker)
- Shock (cardiogenic or hypovolaemic)
- Bradycardia with a heart rate <60bpm
Alternative antihypertensive agents including nifedipine (immediate release) or hydralazine should be used in patients with a contraindication to labetalol use.
- iv labetalol is NOT TGA registered and thus doctors MUST complete a TGA Special Access Scheme (SAS) category A form is mandatory BEFORE administering labetalol - this form is located with the vials and must be faxed to pharmacy
Dose and administration for Rx of pre-eclampsia or eclampsia
- Available as an ampoule of clear fluid containing 100mg/20mL (i.e. 5mg/mL)
- Can be administered iv undiluted through an iv line primed with labetalol, and, preferably through a large bore iv cannula
- Can be administered in same iv line but through a different port, with magnesium sulphate in patients with pre-eclampsia and eclampsia
- adults via syringe driver:
- 100mg in 20mL (5mg/mL) drawn up undiluted into a 20mL syringe
- 1st bolus: 20mg over 2 minutes then flush with 10mL 0.9% saline
- optional 2nd and 3rd boluses if inadequate response within 10 minutes: 20-40mg over 2 minutes then flush with 10mL 0.9% saline (3rd bolus can be increased to 60mg if needed)
- Maintenance infusion:
- Commence at 20mg/hr and titrate according to response
- Discontinue by weaning over 1-2 hours when blood pressure is consistently less than 155 / 95 mm Hg
- If the systolic blood pressure <140mmHg or diastolic <90mmHg cease infusion and consider bolus iv fluid
- Extravasation may cause ischaemia and necrosis due to the low pH of the solution (pH 3.5-4.2). Prior to commencing infusion, flush line with sodium chloride 0.9 % to ensure patent
- The maximum daily dose of labetalol should not exceed 300mg in 24 hours
- Monitor BP regularly - every 5 minutes for 1st 15 minutes after a bolus or after starting infusion then every 15 minutes while on maintenance infusion or for 1st hour after a bolus
- keep patient supine (in left lateral position if pregnant) and beware of orthostatic hypotension for up to 3 hrs following cessation of infusion
Dose for Mx of severe hypertension
- iv bolus:
- 10mg (2mL) given as slow IV injection over 1-2 minutes (given UNDILUTED)
- Dose can be repeated at 10 minute intervals, titrate to desired systolic/diastolic BP
- iv infusion
- 200mg (2 vials = 40mL) into 250mL fluid (withdraw 40ml)
- Infuse at 3mL/minute to give approximately 2.5mg/min
- Maximum dose 300mg in 24 hours
labetalol.txt · Last modified: 2017/07/17 07:09 by 127.0.0.1