What is Lo-Estrol (low-dose estrogen medication) compared to Zoely (estradiol and nomegestrol acetate)?

Lo-Estrol vs. Zoely: Comparison of Contraceptive Options

Zoely is a monophasic combined oral contraceptive containing natural estradiol and nomegestrol acetate, offering potentially better safety profile than Lo-Estrol which typically contains synthetic ethinyl estradiol.

Composition and Key Differences

Lo-Estrol

• Contains synthetic ethinyl estradiol (typically 20-35 μg)
• Combined with a progestin (often a levonorgestrel derivative)
• Traditional 21/7 day regimen (21 active pills, 7 placebo)
• Classified as a "low-dose" combined oral contraceptive (COC)

Zoely

• Contains 1.5 mg nomegestrol acetate (a selective progestogen derived from 19-norprogesterone) 1
• Contains 2.5 mg estradiol (natural estrogen identical to endogenous estrogen) 2, 3
• Extended 24/4 day regimen (24 active pills, 4 placebo days) 2
• First monophasic COC to contain natural estradiol rather than synthetic ethinyl estradiol 2

Safety Profile Comparison

Cardiovascular Risk

• Zoely may have a more favorable cardiovascular profile:
  • Natural estradiol has potentially less impact on thrombosis risk compared to ethinyl estradiol 4
  • In studies, estradiol and nomegestrol acetate showed fewer adverse effects on coagulation and fibrinolysis compared to ethinyl estradiol-based pills 4

Metabolic Effects

• Zoely:

  • Minimal impact on lipid profiles 5
  • Neutral effect on glucose metabolism 5
  • Minimal influence on blood pressure 1
  • Little to no weight gain reported 1

• Lo-Estrol (and other ethinyl estradiol COCs):

  • May have more pronounced effects on lipid metabolism
  • Higher doses of ethinyl estradiol (>35 μg) show statistically higher odds ratios for venous thromboembolism 4

Efficacy

• Zoely demonstrated high contraceptive efficacy in clinical trials, with Pearl Index values comparable to or better than other COCs 2, 1
• Particularly effective in overweight and obese patients 1
• Both provide >90% efficacy with perfect use, similar to other combined hormonal contraceptives 6

Bleeding Pattern

• Zoely:

  • Associated with shorter, lighter periods or absence of withdrawal bleeding 2, 3
  • May have better cycle control due to extended regimen (24/4) 3

• Lo-Estrol:

  • Traditional withdrawal bleeding pattern with 21/7 regimen
  • Bleeding patterns vary based on specific formulation

Side Effects

• Zoely:

  • Most common side effects include acne and abnormal withdrawal bleeding 2
  • Less favorable acne-related outcomes compared to some other COCs 2
  • Fast recovery of ovarian activity after discontinuation 1

• Lo-Estrol:

  • Common transient side effects include irregular bleeding, headache, and nausea 4
  • No reliable evidence linking weight gain or mood changes to use 4

Special Considerations

Medical Conditions

• Both contraceptives should be avoided in women with:
  • Severe uncontrolled hypertension
  • Complicated valvular heart disease
  • Migraines with aura
  • History of thromboembolism 4

Specific Advantages of Zoely

• More selective progestogen with minimal androgenic effects 5
• Natural estrogen component may be appealing to patients seeking more "natural" hormone options 7
• Extended regimen (24/4) may reduce hormone withdrawal symptoms 2

Clinical Decision Making

When choosing between these contraceptives, consider:

1. Cardiovascular risk factors: If patient has risk factors for thromboembolism but still desires a combined pill, Zoely may be preferable due to natural estradiol component

2. Bleeding preferences: For patients who prefer lighter or shorter periods, Zoely's 24/4 regimen may be advantageous

3. Side effect concerns:

   • For patients concerned about weight gain: Zoely shows minimal impact
   • For patients with acne concerns: Lo-Estrol may be preferable

4. Patient preferences: Some patients may prefer the "natural" estrogen in Zoely

5. Specific medical conditions: For patients with hereditary angioedema, progestin-only options may be safer than either combined pill 4

Both medications require prescription and regular follow-up visits to monitor for adverse effects and address adherence issues.