What are the differences between progestin-only (progestin) and combined hormonal (estrogen and progestin) contraceptives?

Differences Between Progestin-Only and Combined Hormonal Contraceptives

Progestin-only contraceptives are safer than combined hormonal contraceptives for patients with thrombosis risk factors, including those with positive antiphospholipid antibodies (aPL), as they do not significantly increase thrombosis risk. 1, 2, 3

Efficacy Comparison

Highly Effective Methods (Failure Rate <1%)

• Long-acting reversible contraceptives (LARC):
  • Copper IUD
  • Progestin IUD (Levonorgestrel)
  • Subdermal progestin implant

Effective Methods (Failure Rate 3-8%)

• Progestin-only methods:
  • Progestin-only pills (5-8% failure rate)
  • Depot medroxyprogesterone acetate (DMPA) (3% failure rate)
• Combined hormonal methods:
  • Combined oral contraceptives (5-8% failure rate)
  • Transdermal patch (5-8% failure rate)
  • Vaginal ring (5-8% failure rate)

Key Differences

1. Thrombotic Risk

• Combined hormonal contraceptives:

  • Increase risk of venous thromboembolism (VTE) by 2-3 fold 3, 4
  • Increase risk of arterial thrombosis by approximately 2-fold 4
  • Contraindicated in patients with positive aPL or history of thrombosis 1, 2

• Progestin-only methods:

  • Generally not associated with increased thrombotic risk 3, 4
  • Exception: DMPA may increase thrombosis risk 3
  • Safe for patients with history of thrombosis or thrombophilia 3

2. Hormonal Composition

• Combined hormonal contraceptives:

  • Contain estrogen (usually ethinylestradiol) and progestin
  • Older progestins (norethisterone, levonorgestrel) have lower VTE risk than newer ones (desogestrel, drospirenone, gestodene) 3, 5

• Progestin-only methods:

  • Contain only progestin without estrogen
  • Different progestins have varying androgenic and anti-mineralocorticoid effects 4

3. Usage in Special Populations

• Patients with SLE:

  • With stable/low disease activity and negative aPL: Both combined and progestin-only methods are acceptable 1
  • With positive aPL: Only progestin-only methods or copper IUDs recommended 1, 2
  • With moderate-high disease activity: IUDs or progestin implants preferred 1

• Patients with rheumatoid arthritis:

  • Progestin IUDs highly recommended regardless of disease activity 2
  • All contraceptive options acceptable if aPL negative 2

4. Administration and Compliance

• Progestin-only pills:

  • Must be taken at the same time every day (within 3-hour window)
  • No pill-free interval
  • Higher rate of breakthrough bleeding than combined methods 1

• Combined oral contraceptives:

  • Slightly more flexible timing
  • Typically includes hormone-free interval
  • More regular bleeding patterns

Clinical Decision Algorithm

1. Assess thrombosis risk factors:

   • Check for positive aPL
   • History of thrombosis
   • SLE diagnosis and activity level
   • Other thrombophilias

2. For patients WITH thrombosis risk factors:

   • Recommend progestin-only methods or copper IUD
   • Prioritize LARCs (IUDs or implants) for highest efficacy
   • Avoid combined hormonal contraceptives and DMPA

3. For patients WITHOUT thrombosis risk factors:

   • Any method is acceptable based on patient preference
   • LARCs still recommended for highest efficacy
   • Consider combined methods if menstrual regulation desired

4. For patients on immunosuppressive therapy:

   • Highly effective contraception essential (LARCs preferred)
   • For mycophenolate users: IUD or combination of two other contraceptive methods 1

Caveats and Pitfalls

• Transdermal estrogen-progestin patch should be avoided in SLE patients due to higher estrogen exposure 1
• DMPA should be avoided in patients at risk for osteoporosis 1
• Emergency contraception is recommended for all patients, including those with SLE or positive aPL, as risks are low compared to unplanned pregnancy 1