SS_OB 1.12 Labetolol

At least where I work we have to fill out the Special Access Scheme form to use IV labetolol, but worldwide it is a commonly drug for blood pressure control in pre-eclampsia, and it has many advantages over hydralazine.

SS_OB 1.12 Describe the pharmacology of agents used for the treatment of pre-eclampsia including magnesium, hydralazine and labetolol


T/F Labetolol is a non specific alpha antagonist

T/F Labetolol is a non specific beta antagonist

T/F A beta blocker with Intrinsic Sympathomimetic Activity is particularly useful for prevention of myocardial infarction

T/F Labetolol may cause profound foetal bradycardia

T/F Cardiac output rises after intravenous but not oral Labetolol


SS_OB 1.11 Describe the pharmacology of tocolytic agents with particular reference to beta 2 agonists, calcium antagonists, magnesium, inhalational anaesthetics, nitrates and NSAIDS

TRUE/FALSE  Sublingual GTN spray can be used as a uterine relaxant during Caesarean section

TRUE/FALSE  The emergency management of eclamptic seizures includes the administration 4g of Magnesium sulphate by intravenous (bolus) injection

TRUE/FALSE  Exposure to NSAIDs after 30 weeks’ gestation is associated with an reduced risk of premature closure of the fetal ductus arteriosus and oligohydramnios

TRUE/FALSE  Nifedipine is contraindicated in pregnant women with pre-existing cardiac disease

TRUE/FALSE  Calcium channel blockers are associated with a higher incidence of neonatal respiratory distress syndrome than other tocolytic drugs

Queen’s Birthday Special

It seems serendipitous that last week’s posts were obstetric related and today is the Queen’s Birthday holiday…

Queen Victoria was a relatively early adopter of anaesthesia and received chloroform anaesthesia for the birth of her 8th and 9th children, Leopold in 1853 and Beatrice in 1857. The chloroform was administered via an open drop technique, during the second stage of labour, with the aim of achieving semi-consciousness. The Queen is quoted as saying the chloroform was “soothing, quieting and delightful beyond measure”


It was James Simpson who, in 1847, first suggested the use of anaesthesia for labour. Initially obstetricians were almost universally opposed to the use of anaesthesia for labour, citing it as unnecessary for a natural process and concerned for the safety aspects.

John Snow, who anaesthetised Queen Victoria on both occasions, was a physician with a career spanning interest in anaesthesia. He experimented widely, on animals, using different inhaled substances in an attempt to find superior anaesthetic agents. He realised that the volatility of an agent declined as it was vaporised , due to the drop in temperature. Consequently he developed and early vaporiser, with a brass chamber which was immersed in water, to minimise temperature fluctuations. He appears to have been a man of great scientific rigour, which likely inspired confidence amongst the Queen’s physicians and eased the path for her to receive anaesthesia, when she and Prince Albert requested it. He was also a strong proponent of a doctor separate to the surgeon administering the anaesthetic. One of his major works On Chloroform and Other Anaesthetics and their Administration was published following his death is 1858. If you click on the title it will take you to a copy of the book, with William Morton’s name handwritten across the top!

John Snow made another great contribution to medicine as an epidemiologist. He was a believer that cholera was transmitted by contaminated water, contrary to popular belief at the time. Following an outbreak in London in 1854, he conducted an extensive epidemiological investigation tracking the details of victims and non victims to identify where they sourced their water. He identified the likely source as a pump on Broad Street, Armed with his research, he went to town officials and convinced them to remove the pump handle, making it impossible to draw water from the pump. The outbreak stopped almost instantly! It wasn’t until 1883 that Vibrio cholerae was isolated by Robert Koch and the means of transmission confirmed.

John Snow died age 45. Just imagine what he might have contributed to our speciality ( and others) if he had lived a long life……


SS_OB 1.10 Pharmacology of oxytocics

Regarding PGF2 alpha:

Q. It increases uterine tone.  TRUE/ FALSE

Q. It can cause bronchoconstriction.  TRUE/ FALSE

Q. It reliably causes systemic hypertension.  TRUE/ FALSE

Q. Can cause a low grade fever.  TRUE/ FALSE

Q. Is administered in small aliquots intravenously.  TRUE/ FALSE

The formulation currently being used in my hospital is sourced from Russia. No one in the Department can read Russian.

SS_OB 1.13 Placental transfer of drugs

Other end of the age spectrum today..

SS_OB 1.13 Explain the factors that influence the transfer of drugs across the placenta

Ionised drugs are more likely to cross the placenta compared with non-ionised drugs T/F

Heparin is safe to use in pregnancy because its large molecular size prevents it crossing the placenta T/F

Weakly basic drugs, with a pKa less than 7.4, may become concentrated in the fetal compartment secondary to increased levels of ionisation T/F

The placenta is capable of metabolising some drugs presented to it T/F

For highly lipid soluble drugs, degree of protein binding is an important factor in the rate of placental drug transfer T/F

SS_OB 1.9 Drug Variability in Pregnancy

SS_OB 1.9 Describe the influence of pregnancy on the pharmacokinetics and pharmacodynamics of drugs commonly used in anaesthesia and analgesia

TRUE/FALSE In pregnancy the average gain of 8 litres of total body water significantly increases the volume of distribution of hydrophilic drugs.

TRUE/FALSE Foetal and placental tissues provide another compartment for drug distribution.

TRUE/FALSE Pseudocholinesterase activity is decreased in pregnancy causing prolongation of succinylcholine block.

TRUE/FALSE Pregnancy reduces MAC by 25-30%.

TRUE/FALSE Nociceptive response thresholds are elevated in pregnancy.