🟦 MASTER TABLE 1 — TERBUTALINE (ZERO-OMISSION)

🟦 MASTER TABLE 2 — TERBUTALINE: DOSES & USES

🟦 MASTER TABLE 3 — TERBUTALINE: ADVERSE EFFECTS, CI, INTERACTIONS

🟦 MASTER TABLE 4 — TERBUTALINE: MONITORING & LABOUR-WARD USE

🟩 MASTER TABLE 5 — ATOSIBAN (ZERO-OMISSION)

🟩 MASTER TABLE 6 — ATOSIBAN: DOSING & SAFETY

🟩 MASTER TABLE 7 — ATOSIBAN: SIDE EFFECTS & CONTRAINDICATIONS

🟨 MASTER TABLE 8 — TERBUTALINE vs ATOSIBAN vs NIFEDIPINE

🧠 ONE-LOOK EXAM LOCK

If you want next:

• 🔁 Single mega-table (all tocolytics including MgSO₄ & indomethacin)
• 🧠 XMind-ready paste version
• 🧪 Exam MCQs built from these tables

Just say which format.

✅ TERBUTALINE

⭐ 1. What is Terbutaline?

• Class: β2-adrenergic agonist (similar to salbutamol)
• Type: Bronchodilator + smooth muscle relaxant
• Forms: Oral tablets, inhaler, IV/SC injection

Main uses:

1️⃣ Asthma & bronchospasm (first use)

2️⃣ Tocolysis (relaxing uterus in preterm labour) – short-term only

3️⃣ Hyperkalemia (shifts K⁺ into cells)

⭐ 2. Mechanism of Action (VERY HIGH YIELD)

Terbutaline stimulates β2-receptors → causes:

A. Smooth Muscle Relaxation

• Bronchi → bronchodilation
• Uterus → relaxes uterine contractions (tocolysis)

B. Metabolic Effects

• ↑ Na⁺/K⁺ ATPase activity → K⁺ moves into cells → ↓ serum potassium
• ↑ glycogenolysis → ↑ blood glucose

C. Cardiovascular Effects

• Mild β1 spillover → ↑ heart rate, palpitations, tremors

👉 Think: β2 = “breathing + baby relax”

⭐ 3. Pharmacokinetics

• Onset:
• Inhaled: 5 minutes
• SC: 5–15 minutes
• IV: almost immediate
• Duration: 3–6 hours
• Metabolism: Liver
• Excretion: Urine
• Crosses placenta: Yes
• Crosses into breast milk: Yes (minimal risk)

⭐ 4. Clinical Uses

🔵 A. Asthma / Bronchospasm

• Causes rapid bronchodilation
• Used in:
• Acute asthma exacerbations
• Exercise-induced bronchospasm
• COPD (less common)

Dose:

• Inhaled: 1–2 puffs
• SC: 0.25 mg, may repeat to max 0.5 mg
• IV infusion: Rare, in severe asthma

🔵 B. Tocolysis (OBGYN HIGH-YIELD)

Used to delay preterm labour for 24–48 hours to allow:

• Steroids for fetal lung maturity
• Transfer to tertiary unit

Dose (tocolysis):

• SC injection: 0.25 mg every 20 min (max 3 doses)
• IV infusion: 0.08–0.1 mg/min

Important:

🚫 Not recommended for long-term use

🚫 FDA black box warning for prolonged use (>48–72 hrs) → maternal risk

Used only as emergency short-term relaxation.

🔵 C. Hyperkalemia

• β2 stimulation → shifts K⁺ into cells
• Used when:
• IV salbutamol unavailable
• Combination with insulin/dextrose

⭐ 5. Side Effects (VERY HIGH YIELD)

Maternal

• Tachycardia
• Palpitations
• Tremor
• Hyperglycemia
• Hypokalemia
• Hypotension
• Pulmonary edema (rare but dangerous)
• Headache, nausea

Fetal

• Fetal tachycardia
• Neonatal hypoglycemia
• Fetal arrhythmias (rare)

👉 β2 agonists activate sympathetic pathways → fast heart, shaky body.

⭐ 6. Contraindications

❌ Maternal cardiac disease

❌ Uncontrolled hyperthyroidism

❌ Uncontrolled diabetes

❌ Severe preeclampsia/eclampsia

❌ Placental abruption / hemorrhage

❌ Intrauterine infection

❌ Significant cardiac arrhythmias

⭐ 7. Drug Interactions

• MAO inhibitors / TCAs → hypertensive crisis
• Beta-blockers → oppose effect
• Other sympathomimetics → arrhythmias, severe tachycardia
• Diuretics → worsen hypokalemia
• Corticosteroids → worsen hypokalemia

⭐ 8. Monitoring (Extremely Important in OBGYN)

During tocolysis, monitor:

Mother:

• HR (stop if >120 bpm)
• BP
• Chest pain
• Breathlessness
• Glucose
• Potassium
• Fluid balance (risk pulmonary edema)

Fetus:

• Fetal heart monitoring
• Signs of tachycardia or distress

⭐ 9. Why It Is NOT Preferred Anymore (Exam Point)

• Significant maternal side effects
• Increased risk of pulmonary edema
• Better alternatives available:
• Nifedipine (first-line tocolytic)
• Atosiban (fewest maternal SE, expensive)

⭐ 10. Terbutaline vs Nifedipine vs Atosiban (Quick Recall)

⭐ 11. Terbutaline in Labour Ward – When Used?

Emergency uterine relaxation such as:

• Fetal bradycardia with hypertonic contractions
• Uterine tachysystole due to oxytocin
• Manual rotation of fetal head
• Shoulder dystocia (to relax uterus)
• Breech extraction (rare)

Dose: 0.25 mg SC → rapid relaxation in minutes.

👉 Think: When uterus is too tight to do a maneuver → give terbutaline.

⭐ 12. In Summary (Memorise This)

*Terbutaline = β2 agonist

→ bronchodilation

→ uterine relaxation

→ ↓ potassium

→ fast onset

→ major side effects (tachycardia, hypokalemia, pulmonary edema).**

*Use short-term only.

Nifedipine/Atosiban preferred for long-term tocolysis.**

🧠 Integrated Clinical Scenario — TERBUTALINE (ZERO-OMISSION)

📍 Setting

A 28-year-old G2P1 woman, 30+4 weeks gestation, arrives at the labour ward with painful, regular uterine contractions every 3–4 minutes for the past 2 hours.

She has:

• No vaginal bleeding
• No fever or leaking
• BP: 110/70 mmHg
• Pulse: 104 bpm
• Chest clear
• CTG: Reactive, baseline fetal HR 145 bpm

On vaginal examination:

• Cervix: 2 cm dilated, 50% effaced

→ Diagnosis: Preterm labour

🔴 Immediate Clinical Goal

Not to stop labour permanently, but to delay delivery for 24–48 hours to allow:

• Antenatal corticosteroids (betamethasone) for fetal lung maturity
• Possible transfer to a tertiary NICU unit

💉 Drug Chosen: TERBUTALINE

Why?

• Needs rapid uterine relaxation
• Short-term emergency tocolysis only

⚙️ Mechanism at Bedside (What is happening physiologically)

Terbutaline is given 0.25 mg SC.

At the receptor level:

• Stimulates β2-adrenergic receptors

Effects immediately after injection:

🫁 Smooth muscle

• Uterus → relaxes → contractions reduce
• Bronchi → bronchodilation (useful if asthmatic)

🔬 Metabolic

• ↑ Na⁺/K⁺-ATPase → K⁺ shifts into cells
• Serum potassium starts falling → risk hypokalemia
• ↑ Glycogenolysis → ↑ blood glucose

❤️ Cardiovascular (β1 spillover)

• ↑ Heart rate
• Palpitations
• Tremors

👉 Clinically remembered as:

“β2 = breathing + baby relax”

⏱️ Timeline in the Ward

• Within 5–10 minutes:
• Uterine contractions soften and space out
• Patient feels tremulous
• Pulse rises to 118 bpm
• CTG:
• Fetal HR increases to 160 bpm → fetal tachycardia (expected)

👀 Monitoring (CRITICAL — EXAM + REAL LIFE)

👩 Mother

• HR (STOP if >120 bpm)
• BP
• Chest symptoms (dyspnea → pulmonary edema red flag)
• Blood glucose
• Serum potassium
• Strict fluid balance

👶 Fetus

• Continuous CTG
• Watch for persistent tachycardia or distress

⚠️ Complication Awareness in the Scenario

After 30 minutes:

• Patient complains of palpitations and chest tightness
• HR now 122 bpm
• Fine basal crepitations heard

👉 Immediate action:

• STOP terbutaline
• Oxygen
• Restrict fluids
• Evaluate for pulmonary edema

This highlights why prolonged use is dangerous.

🚫 Why Terbutaline is NOT Continued Long-Term

• High maternal side-effect burden
• Risk of:
• Pulmonary edema
• Severe tachyarrhythmias
• Hypokalemia
• Hyperglycemia
• FDA black-box warning if used >48–72 hours

🔁 What is Used Next (Standard of Care)

Once contractions are controlled short-term:

• Switch to Nifedipine (oral Ca²⁺ channel blocker)
• Effective
• Fewer maternal side effects

Or if available:

• Atosiban (oxytocin receptor antagonist)
• Safest for mother
• Expensive

🚑 Another Labour Ward Emergency (Same Drug, Different Use)

Later in the same ward:

• Another patient on oxytocin infusion develops:
• Uterine tachysystole
• Prolonged fetal bradycardia

Immediate management:

• Stop oxytocin
• Left lateral position
• Oxygen
• Terbutaline 0.25 mg SC

→ Rapid uterine relaxation

→ Pressure off placenta

→ Fetal heart rate recovers

🎯 Exam-Perfect Closing Statement

Terbutaline is a fast-acting β2-agonist used for emergency short-term uterine relaxation in preterm labour or intrapartum emergencies. It relaxes smooth muscle, shifts potassium intracellularly, and causes maternal tachycardia. Because of serious maternal side effects—especially pulmonary edema—it is NOT preferred for long-term tocolysis, where nifedipine or atosiban are safer alternatives.

🧠 ONE-LINE MEMORY LOCK

Tight uterus + urgent maneuver → Terbutaline SC → fast relax → stop early.

✅ ATOSIBAN

⭐ 1. What is Atosiban?

• Oxytocin receptor antagonist
• Used for tocolysis (stopping preterm labour)

👉 Blocks oxytocin = uterus relaxes.

⭐ 2. Mechanism (MOST IMPORTANT)

• Blocks oxytocin receptors in:
• Uterine myometrium → ↓ contractions
• Decidua → ↓ prostaglandin release

▶ Result:

✔ Contractions reduce

✔ Cervical change slows

✔ Labour is delayed 48 hours (enough for steroids)

• Competitive antagonist of oxytocin receptors in uterus
• Blocks:
• Oxytocin-mediated ↑ intracellular Ca²⁺
• Prostaglandin release (via decidual cells)
• Result → uterine relaxation + ↓ contractions

How IP₃ normally works in the uterus

When oxytocin binds to its receptor on uterine smooth muscle:

1. The receptor activates Gq protein
2. Gq activates phospholipase-C (PLC)
3. PLC cleaves PIP₂ into:
• IP₃
• DAG
4. IP₃ binds to receptors on the sarcoplasmic reticulum
5. This causes Ca²⁺ release into cytoplasm
6. Higher intracellular Ca²⁺ → actin-myosin interaction → uterine contraction

So does IP₃ help?

Not “help” in treatment, but IP₃ helps contract the uterus.

Atosiban blocks the oxytocin receptor → preventing the Gq-PLC-IP₃ pathway → preventing Ca²⁺ release → reducing uterine contraction.

Quick link to atosiban

• Oxytocin receptor active → IP₃ ↑ → Ca²⁺ ↑ → contraction
• Atosiban antagonizes receptor → IP₃ ↓ → Ca²⁺ ↓ → relaxation

So IP₃ is a key second messenger in uterine contraction physiology, and blocking the pathway is why atosiban acts as a tocolytic.

⭐ 3. Why is Atosiban Preferred? (Exam Favourite)

• Safest tocolytic for the mother
• Fewest cardiovascular side effects
• Safe in women with cardiac disease
• No fetal tachycardia

👉 Best tolerated tocolytic.

⭐ 4. Dosing (Must Know Pattern)

Three-step regimen:

1️⃣ Bolus: 6.75 mg IV over 1 minute

2️⃣ Loading infusion: 18 mg/hour for 3 hours

3️⃣ Maintenance infusion: 6 mg/hour for up to 45 hours

⏱ Max total duration: 48 hours

⭐ 5. Side Effects (VERY FEW)

• Nausea
• Headache
• Vomiting
• Flushing

👉 No tachycardia, no hypokalemia, no palpitations.

⭐ 6. Contraindications (Know the Pattern)

❌ Absolute

• GA ≥ 34 weeks
• PPROM with infection
• Antepartum hemorrhage
• Fetal distress
• IUGR with abnormal Dopplers
• Maternal instability

❌ Relative

• Liver/renal impairment (caution)

⭐ 7. Advantages vs Other Tocolytics

👉 Cleanest side-effect profile.

⭐ 8. Effectiveness

• Delays labour 48 hours but no proven improvement in neonatal outcomes.
• Purpose: Give steroids time + transfer mother.

⭐ 9. When You Choose Atosiban

• First choice in Europe
• Maternal cardiac disease
• Borderline BP
• Previous severe reaction to β-agonists or nifedipine

Clinical scenario: Atosiban used properly (and why it’s the “clean” tocolytic)

A 29-year-old primigravida at 31+4 weeks comes to labour ward with painful, regular lower abdominal tightenings for 4 hours.

Assessment

• Contractions: every 4–5 min, lasting ~40–50 s
• Speculum: membranes intact, no bleeding, no leaking
• VE: cervix 2 cm, 60% effaced (so true preterm labour: contractions + cervical change)
• CTG: reassuring (no fetal distress)
• Temp normal, no uterine tenderness, no foul discharge (no infection)
• Ultrasound/Doppler: normal growth + normal Dopplers (so no IUGR with abnormal Dopplers)
• Past history: maternal cardiac disease (e.g., repaired congenital heart disease / cardiomyopathy history) and she previously got palpitations with inhaled β-agonist for asthma.

Now you have the classic exam decision point:

✅ She is <34 weeks

✅ No APH

✅ No PPROM with infection (and no infection signs at all)

✅ No fetal distress

✅ Mother stable

✅ Goal: buy 48 hours for steroids + arrange in-utero transfer if needed

So you choose Atosiban.

Why Atosiban works (tie your physiology to the drug)

You explain to the team:

Normally, oxytocin binds oxytocin receptors on uterine myometrium → activates Gq → PLC → splits PIP2 → IP3 + DAG.

• IP3 goes to sarcoplasmic reticulum → Ca2+ release into cytoplasm
• Ca2+ rises → actin–myosin interaction → uterine contraction

Also, oxytocin acts at the decidua → increases prostaglandin release, which further strengthens contractions and cervical change.

Atosiban = competitive oxytocin receptor antagonist

• Blocks receptor on:
• Myometrium → blocks Gq–PLC–IP3 → Ca2+ rise → contractions reduce
• Decidua → ↓ prostaglandin release

➡️ Net effect: uterus relaxes, contractions drop, cervical change slows.

(So yes: IP3 “helps” contraction in normal physiology, and atosiban prevents that pathway by blocking the receptor upstream.)

Why it’s preferred here (exam favourite justification)

Because she has cardiac disease and is borderline sensitive to β-agonists:

• Atosiban is best tolerated / safest for mother
• Fewest cardiovascular side effects
• Safe in women with cardiac disease
• No fetal tachycardia

So compared with alternatives:

• Not terbutaline: avoids tachycardia / palpitations / pulmonary edema risk
• Not nifedipine (in a “borderline BP” patient): avoids hypotension
• Not indomethacin: avoids ductus closure + oligohydramnios
• Not MgSO4 as a primary tocolytic: avoids more toxicity (and MgSO4 is mainly for other indications like neuroprotection depending on protocol)

Dosing (3-step pattern in the scenario)

You start atosiban exactly by the book:

1. Bolus: 6.75 mg IV over 1 minute
2. Loading infusion: 18 mg/hour for 3 hours
3. Maintenance infusion: 6 mg/hour for up to 45 hours

⏱ Total maximum treatment time = 48 hours.

Purpose of this 48-hour window:

• Give antenatal corticosteroids time to work
• Arrange transfer to a centre with NICU if needed

Side effects you actually expect (and what you DON’T expect)

During infusion she feels a bit unwell:

• Nausea
• Headache
• Vomiting
• Flushing

And you point out what makes it “clean”:

• No tachycardia
• No hypokalemia
• No palpitations

Contraindications (you actively check them in the scenario)

Before continuing, you document you excluded:

Absolute “don’t tocolyse” pattern in ATOSIBAN

• GA ≥34 weeks (she’s 31+4 → ok)
• PPROM with infection (no PPROM, no infection → ok)
• Antepartum hemorrhage (none → ok)
• Fetal distress (CTG reassuring → ok)
• IUGR with abnormal Dopplers (normal Dopplers → ok)
• Maternal instability (stable → ok)

Relative

• Liver/renal impairment → use caution (you check LFT/renal function if indicated)

Effectiveness (the honest exam line)

At 2–3 hours, contractions space out and cervix stabilizes.

You state the key exam truth:

• Atosiban delays labour ~48 hours
• But there is no proven improvement in neonatal outcomes
• Its purpose is time for steroids + safe transfer (not “magic cure”)

One-line viva finish

“In a <34-week true preterm labour, with no contraindications and especially in maternal cardiac disease / borderline BP, atosiban is chosen because it blocks oxytocin receptors → prevents Gq–PLC–IP3–Ca2+ contraction pathway and reduces prostaglandins, giving a 48-hour window for steroids and transfer, with **minimal side effects and no tachycardia.”