MRCOG Part 1: Pharmacology - Essential Study Guide

This is your essential guide to the Pharmacology section of the MRCOG Part 1 exam. We built it from our own experience of sitting the exam, the RCOG syllabus and the official reading list. It lists the pharmacology concepts most often tested, section by section.

Why Pharmacology matters in MRCOG Part 1

Pharmacology is crucial for understanding the mechanisms, effects, and safe use of drugs in obstetrics and gynaecology. The MRCOG Part 1 exam will test your knowledge of drug classifications, pharmacokinetics, pharmacodynamics, and their clinical applications in managing various conditions related to women's health, pregnancy, and the foetus.

Pharmacology syllabus, section by section

IPharmacokinetics and Pharmacodynamics

Pharmacokinetics (Pk)

Drug Absorption
  • Routes of administration (oral, intravenous, etc.)
  • Factors affecting absorption (lipid solubility, pH, etc.)
  • Bioavailability and first-pass metabolism
Drug Distribution
  • Volume of distribution
  • Protein binding
  • Tissue penetration (blood-brain barrier, placental transfer)
Drug Metabolism
  • Phase I and Phase II reactions
  • Cytochrome P450 enzyme system
  • Enzyme induction and inhibition
Drug Elimination
  • Renal and hepatic clearance
  • Half-life
  • Factors affecting elimination (renal/liver function)

Pharmacodynamics

Drug-Receptor Interactions
  • Agonists, antagonists, partial agonists
  • Receptor types (ion channels, G-protein coupled, etc.)
Dose-Response Relationships
  • Therapeutic window
  • Potency and efficacy
  • Toxicity and side effects

IIObstetric Pharmacology

Antihypertensives in Pregnancy

Labetalol
  • Mechanism of action (alpha and beta blockade)
  • Use in pregnancy and pre-eclampsia
  • Potential side effects (fetal growth restriction, neonatal hypoglycemia)
Methyldopa
  • Mechanism of action (central alpha-2 agonist)
  • Use in pregnancy
  • Side effects (rebound hypertension, depression, hemolytic anaemia)
Nifedipine
  • Mechanism of action (calcium channel blocker)
  • Use in pregnancy and as a tocolytic
  • Side effects (hypotension, peripheral edema)
Hydralazine
  • Mechanism of action (vasodilator)
  • Use in acute hypertension in pregnancy
  • Side effects (hypotension, lupus-like syndrome)
ACE Inhibitors and ARBs
  • Contraindication in pregnancy
  • Associated risks (congenital malformations, oligohydramnios, fetal renal impairment)

Tocolytics

Nifedipine
  • Mechanism of action in tocolysis
  • Off-label use
  • Comparison with other tocolytics
Atosiban
  • Mechanism of action (oxytocin antagonist)
  • Side effects and comparison with other tocolytics
Beta-sympathomimetics (Salbutamol, Ritodrine, Terbutaline)
  • Mechanism of action
  • Side effects (tachycardia, hypotension, pulmonary oedema)
  • Current guidelines regarding their use
Magnesium Sulfate
  • Use for neuroprotection in preterm labor
  • Mechanism of action

Analgesia in Pregnancy and Labour

Paracetamol
  • Safety in pregnancy
  • Use for mild pain relief
NSAIDs
  • Use of low-dose aspirin in high-risk pregnancies
  • Risks associated with NSAID use (miscarriage, fetal renal impairment, premature closure of ductus arteriosus)
  • Contraindication in pregnancy
Opioids
  • Use for moderate to severe pain relief
  • Examples (codeine, dihydrocodeine, pethidine, morphine)
  • Side effects (nausea, vomiting, sedation, constipation, neonatal respiratory depression)
Entonox
  • Composition (nitrous oxide/oxygen mix)
  • Use in labor
  • Side effects
Epidural Analgesia
  • Components (bupivacaine, fentanyl)
  • Benefits for pain relief
  • Side effects and complications

Drugs in the Third Stage of Labour

Syntometrine
  • Composition (ergometrine and oxytocin)
  • Mechanism of action
  • Side effects (nausea, vomiting, hypertension)
  • Contraindications
Syntocinon
  • Mechanism of action (synthetic oxytocin)
  • Use in postpartum hemorrhage (PPH)
Misoprostol
  • Mechanism of action (PGE1 analogue)
  • Use in PPH
  • Side effects
Carboprost
  • Mechanism of action (PGF2a analogue)
  • Use in PPH
  • Caution in hypertension and asthma

Drugs in Breastfeeding

General Principles
  • Factors influencing drug transfer into breast milk
  • Potential effects of drugs on the neonate
Drugs Contraindicated in Breastfeeding
  • Cytotoxics
  • Mood stabilizers (lithium)
  • Sedatives (benzodiazepines, barbiturates)
  • Amiodarone
  • Certain antibiotics (tetracyclines, metronidazole, chloramphenicol)
  • Theophylline
  • Aspirin

IIIGynaecological Pharmacology

Drugs for Menorrhagia

Mefenamic Acid
  • Mechanism of action (NSAID)
  • Use in dysmenorrhea and menorrhagia
  • Side effects
Tranexamic Acid
  • Mechanism of action (antifibrinolytic)
  • Use in menorrhagia
  • Side effects
Combined Oral Contraceptive Pill (COCP)
  • Use in menorrhagia and dysmenorrhea
  • Evidence for effectiveness
Levonorgestrel-Releasing Intrauterine System (LNG-IUS)
  • Mechanism of action
  • Effectiveness compared to other treatments
  • Side effects
Progestogens
  • Cyclical regimens for menorrhagia
  • 21-day regimen and its role
  • Limitations and side effects
  • Efficacy compared to other treatments
Danazol
  • Mechanism of action
  • Use in menorrhagia
  • Limitations due to side effects

Hormonal Treatment of Endometriosis

Oral Oestrogens and Progestogens
  • Use of COCP in endometriosis-related pain
  • Long-cycle use of COCP
  • Mechanism of action of progestogens in endometriosis
Levonorgestrel-Releasing Intrauterine System (LNG-IUS)
  • Mechanism of action in endometriosis
Danazol
  • Effectiveness in endometriosis
  • Limitations due to side effects
Gonadotrophin-Releasing Hormone (GnRH) Analogues
  • Mechanism of action
  • Use in endometriosis
  • Side effects (hypoestrogenic symptoms, bone loss)
  • Add-back therapy

Urogynaecological Agents

Urge Incontinence
  • Antimuscarinic agents (tolterodine, oxybutynin)
  • Mechanism of action
  • Side effects (dry mouth, constipation, dizziness)
Stress Urinary Incontinence
  • Duloxetine (serotonin and noradrenaline reuptake inhibitor)
  • Mechanism of action
  • Side effects

Chemotherapy in Gynaecological Oncology

Classes of Cytotoxic Agents
  • Antimetabolites
  • Alkylating agents
  • Intercalating agents
  • Anti-tumor antibiotics
  • Drugs directed against spindle microtubules
Common Regimens
  • Ovarian cancer (platinum-based regimens)
  • Endometrial cancer (carboplatin, paclitaxel, doxorubicin, cisplatin)
  • Cervical cancer (cisplatin with radiotherapy)
  • Vulval cancer (5-FU, cisplatin)
  • Trophoblastic disease (methotrexate, EMA-CO)
Side Effects of Chemotherapy
  • Hematological (bone marrow suppression)
  • Gastrointestinal (nausea, vomiting, mucositis, diarrhoea)
  • Alopecia
  • Neurological (peripheral neuropathy, tinnitus)
  • Constitutional (lethargy, anorexia)

Hormone Replacement Therapy (HRT)

Indications and Benefits
  • Treatment of climacteric symptoms (hot flushes, night sweats, vaginal dryness)
  • Prevention of osteoporosis (although use has declined due to other risks)
Risks
  • Venous thromboembolism
  • Gallbladder disease
  • Stroke
  • Breast cancer (particularly with long-term therapy)
Endometrial Cancer and Unopposed Oestrogen Use
  • Increased risk with unopposed oestrogen
  • Importance of adding progestogens to HRT regimens
Oestrogen and Progestogen Use in HRT
  • Histological changes produced by progestogens
  • Recommended duration of progestogens to protect the endometrium
  • Risks associated with long-cycle HRT regimens
  • Effects of continuous combined HRT on endometrial cancer risk
Oestrogen Therapy: Routes of Administration and Dosage
  • Oral vs. parenteral administration
  • Transdermal patches (types, frequency of use, side effects)
  • Vaginal creams, pessaries, or rings
  • Subcutaneous implantation (use, duration, risks)
Long-Term Risks and Benefits of HRT
  • Effects on venous thromboembolism, gallbladder disease, stroke, and breast cancer
  • Effects on osteoporosis
The Use of Progestogens Alone
  • Effectiveness in treating hot flushes
  • Effect on other menopausal symptoms
  • Potential to preserve bone density
Tibolone
  • Synthetic steroid with estrogenic, progestogenic, and androgenic properties
  • Use as an alternative to estrogen/progestogen HRT
  • Effects on the endometrium
  • Comparison to continuous combined HRT
  • Adverse effects

IVOther Important Drugs

Local Anesthetics

Amides vs. Esters
  • Examples of amides (lidocaine)
  • Examples of esters (benzocaine, cocaine, procaine, tetracaine)

Neuromuscular Junction Agents

Acetylcholine Release Inhibitors
  • Aminoglycosides

Autonomic Nervous System Agents

Sympathetic Preganglionic Neurotransmitter
  • Acetylcholine
Alpha 2 Agonists
  • Methyldopa

Anticoagulants

Warfarin
  • Mechanism of action (inhibition of vitamin K-dependent clotting factors II, VII, IX, X)
  • Target INR range for deep vein thrombosis
  • Teratogenic effects
  • Use in pregnancy
Low Molecular Weight Heparin (LMWH)
  • Mechanism of action
  • Use in pregnancy
  • Timing of epidural catheter removal after LMWH administration
Rivaroxaban
  • Management of anticoagulation in pregnancy when a patient is on rivaroxaban

Anti-emetics

Cyclizine
  • Mechanism of action (H1 antagonist)
Ranitidine
  • Mechanism of action (H2 antagonist)
  • Effect on gastric acid content and production
Metoclopramide
  • Risk of extrapyramidal side effects

Antibiotics

Ciprofloxacin
  • Mechanism of action (inhibition of DNA gyrase)
Treatment of Pelvic Inflammatory Disease
  • Appropriate antibiotic regimens

Thyroid-Related Drugs

Propylthiouracil
  • Use in pregnancy for thyrotoxicosis
  • Mechanism of action (prevention of peripheral deiodination of thyroxine)

Chemotherapeutic Agents

Methotrexate
  • Mechanism of action (inhibition of dihydrofolate reductase)

Other Agents

Tranexamic Acid
  • Mechanism of action (inhibition of plasmin formation)
Ferric Carboxymaltose
  • Electrolyte disturbance associated with long-term use
Clomifene Citrate
  • Reason for limiting use to 6 cycles

Drugs and Congenital Abnormalities

Warfarin
  • Combination of abnormalities caused by warfarin in pregnancy
Valproate
  • Association with autism in the child when taken in pregnancy

Supplements in Pregnancy

Vitamin D
  • Main reason for taking vitamin D during pregnancy
Low-Dose Aspirin
  • Use from 12 weeks of gestation to prevent pre-eclampsia
  • High-risk factors for pre-eclampsia

How to master Pharmacology

  • Review: work through each section systematically and understand the core concepts before moving on.
  • Active learning: draw diagrams, build mind maps and explain concepts to someone else.
  • Test yourself: try our free practice questions, then work through the pharmacology questions in the Uterio question bank.

Additional resources