Contraception formulation

Question 1

Learning outcomes of contraception formulation lecture

Answer 1

• Recall formulations used in contraception
• Explain how formulation influences release & efficacy
• Understand LARCs (formulation + clinical)
• Compare LARCs vs oral dosing (pros/cons)

Question 2

Formulation-based categories of contraceptives

Answer 2

• Oral: COC, POP
• Non‑oral hormonal: patch, vaginal ring
• LARCs: IUS, IUD, injections, implants

Question 3

General issues with oral contraceptives

Answer 3

• Immediate‑release tablets
• First‑pass metabolism
• Variable plasma concentrations
• Adherence problems

Question 4

Example COC (Mercilon®) contents

Answer 4

• Ethinylestradiol 20 µg
• Desogestrel 150 µg

Question 5

Key excipients in COC tablets and functions

Answer 5

• dl‑alpha‑tocopherol: antioxidant
• Potato starch: disintegrant
• Povidone (PVP): binder/dispersant
• Stearic acid: lubricant/emulsifier
• Aerosil (colloidal silica): glidant
• Lactose: diluent

Question 6

COC packaging and its clinical importance

Answer 6

• PVC/aluminium blister packs (21 tablets)
• Reinforces cyclical dosing
• Part of medication safety (mix‑up recalls)

Question 7

Clinical features of COCs

Answer 7

• Reliable & reversible
• Lower PID risk vs IUD/IUS
• Contraindications: hypertension, VTE risk

Question 8

POP example (Cerazette®)

Answer 8

• Desogestrel 75 µg
• Used when oestrogen contraindicated

Question 9

Cerazette tablet core excipients

Answer 9

• Lactose: diluent
• Maize starch: disintegrant
• Povidone: binder
• Silica: flow aid
• Stearic acid: lubricant
• α‑tocopherol: stabiliser

Question 10

Cerazette film coating excipients

Answer 10

• Hypromellose
• Macrogol 400
• Talc

Question 11

Cerazette pharmacokinetics – absorption

Answer 11

• Rapid absorption
• Converted to etonogestrel (active)
• Peak ~1.8 h
• Bioavailability ≈70%

Question 12

Cerazette pharmacokinetics – distribution & metabolism

Answer 12

• 95.5–99% protein bound (albumin, SHBG)
• Hydroxylation/dehydrogenation to ENG
• Sulphate & glucuronide conjugation

Question 13

Cerazette pharmacokinetics – elimination

Answer 13

• Half‑life ~30 h
• Steady state 4–5 days
• Urine:faeces 1.5:1

Question 14

Cerazette and breastfeeding

Answer 14

• Excreted in breast milk
• Infant exposure extremely low (0.01–0.05 µg)

Question 15

Problems with multiple oral dosing

Answer 15

• Peak–trough fluctuations
• Side effects at peaks
• Failure at troughs
• Poor adherence

Question 16

Zero‑order drug release

Answer 16

• Constant release rate
• Independent of concentration

Question 17

Advantages of zero‑order release

Answer 17

• Avoid peaks & troughs
• Reduced toxicity
• Improved symptom control
• Better adherence

Question 18

Definition of LARCs

Answer 18

• Contraception given < once per month
• Highly effective and reversible

Question 19

Examples of LARCs

Answer 19

• IUS
• Copper IUD
• Injectable progestogens
• Subdermal implants

Question 20

General benefits of LARCs

Answer 20

• Near zero‑order release
• Stable plasma levels
• Reduced user error
• Long duration single administration

Question 21

Mirena® IUS drug release

Answer 21

• Levonorgestrel
• ~20 µg/day initial
• Duration ~5 years
• Local effect → minimal systemic effects

Question 22

Mechanism of IUS

Answer 22

• Endometrial thinning
• Thickened cervical mucus
• Impaired sperm motility
• Partial ovulation suppression

Question 23

IUS device design

Answer 23

• T‑shaped polyethylene frame
• Barium sulfate (radiopaque)
• Hormone‑elastomer core
• Rate‑controlling PDMS membrane

Question 24

Copper IUD mechanism

Answer 24

• Copper acts as spermicide
• Prevents fertilisation

Question 25

Copper IUD efficacy factors

Answer 25

• Depends on copper surface area • ≥380 mm² most effective

Question 26

Copper IUD materials

Answer 26

• Polyethylene T‑frame • Copper wire 107–141 mg • Silver core prevents fragmentation

Question 27

Injectable contraception types

Answer 27

• Depo‑Provera (aqueous suspension) • Sayana Press (aqueous) • Noristerat (oily solution)

Question 28

Aqueous suspension depot mechanism

Answer 28

• Poor solubility • Dissolution‑controlled release • Noyes‑Whitney kinetics

Question 29

Oily depot injections

Answer 29

• Ester prodrug • Partition/diffusion controlled • Hydrolysed in blood to active drug

Question 30

Subdermal implant (Nexplanon®) facts

Answer 30

• Etonogestrel 68 mg • 40 mm × 2 mm rod • Duration 3 years • Radiopaque

Question 31

Nexplanon formulation

Answer 31

• EVA polymer core + drug • Barium sulfate radiopacity • Magnesium stearate

Question 32

Nexplanon release control

Answer 32

• EVA rate‑controlling membrane • Hybrid reservoir‑matrix system

Question 33

Why LARCs better than pills (release profile)

Answer 33

• Stable plasma levels • Improved adherence

Question 34

MCQ concept – film coating excipient

Answer 34

• Titanium dioxide likely film‑coat pigment

Question 35

SAQ concept – reasons LARCs preferred

Answer 35

• Near zero‑order release • Avoid plasma fluctuations