Monophasic Combined Oral Contraceptives Containing 30-50 µg Ethinyl Estradiol Available in Canada
Marvelon (desogestrel 150 µg/ethinyl estradiol 30 µg) is a widely available monophasic combined oral contraceptive in Canada that meets the specified criteria and has demonstrated excellent efficacy, cycle control, and safety in large-scale clinical trials. 1, 2
Primary Recommendation
For a woman of childbearing age with no contraindications seeking a monophasic COC containing 30-50 µg ethinyl estradiol, Marvelon represents an evidence-based first-line option in Canada. 1, 2, 3
Key Features of Marvelon
Composition: Contains 150 µg desogestrel (third-generation progestin) and 30 µg ethinyl estradiol in a monophasic formulation 4, 1
Contraceptive efficacy: Demonstrated Pearl index of essentially zero in large multicenter trials, with only one pregnancy occurring when two consecutive tablets were forgotten 1, 2
Cycle control: Provides excellent cycle control with reported decreases in duration and amount of withdrawal bleeding during consecutive treatment cycles and low incidence of irregular bleeding 1, 2
Safety profile: No adverse effects on blood pressure during 2 years of use, well tolerated with low incidence of minor side effects that decrease further in subsequent cycles 1, 2
Alternative Formulations in the 30-50 µg Range
While the evidence provided focuses primarily on formulations with 30-35 µg ethinyl estradiol, several monophasic options exist:
Levonorgestrel-containing formulations: Second-generation progestin options with 30 µg ethinyl estradiol demonstrate a safer coagulation profile compared to newer progestins 5
Norgestimate-containing formulations: Available with 35 µg ethinyl estradiol, recommended by the American Academy of Pediatrics as a first-line option 5
Important Safety Considerations
Cardiovascular Risk Profile
VTE risk: All COCs increase venous thromboembolism risk from baseline 1-5 per 10,000 woman-years to 3-9 per 10,000 woman-years 6
Desogestrel-specific risk: COCs containing desogestrel with 30-35 µg ethinyl estradiol show 50-80% higher VTE risk compared to levonorgestrel-containing formulations 6
Risk contextualization: This absolute risk remains lower than pregnancy-associated VTE risk (5-20 per 10,000 woman-years) and significantly lower than postpartum risk (40-65 per 10,000 woman-years) 6
Blood Pressure Effects
Ethinyl estradiol effects: At doses of 30-50 µg, blood pressure elevations can occur through RAAS activation, though risk may not be strictly dose-dependent within this range 6
Monitoring requirement: Blood pressure should be assessed at baseline and monitored regularly throughout treatment 6, 5
Absolute Contraindications
Do not prescribe if the patient has: 6, 5
- Active or history of venous thromboembolism or thrombophilia
- Uncontrolled hypertension (severe)
- Migraines with aura or focal neurologic symptoms
- Current or history of breast cancer
- Active liver disease with abnormal function
- Complicated valvular heart disease
- Diabetes with vascular complications
- Smoking in women ≥35 years old (for MI/stroke risk)
Clinical Pearls for Prescribing
Initiation: Can use "quick start" method on the same day as visit in healthy, non-pregnant individuals, with backup contraception for first 7 days 5
Prescription duration: Prescribe up to 1 year at a time per CDC recommendations 5
Drug interactions: Be aware that rifampin, rifabutin, certain anticonvulsants (phenytoin, carbamazepine, barbiturates, topiramate), and some antiretrovirals significantly reduce effectiveness 6, 5
Non-contraceptive benefits: Desogestrel-containing formulations may provide particular benefit for androgen-induced skin disorders including acne due to high selectivity and lack of interference with SHBG increases 3
Comparative Considerations
Second-generation vs third-generation progestins: While levonorgestrel (second-generation) has a more favorable thrombotic profile, desogestrel (third-generation) in Marvelon has been the most widely prescribed COC in Europe for decades with extensive safety data 3
No clear superiority: Among low-dose pills in the 30-35 µg range, there are no clear data suggesting one formulation is superior to another for most users 5
Metabolic effects: Desogestrel formulations show statistically significant increases in HDL cholesterol with LDL usually unchanged or reduced, and little effect on glucose tolerance 3