Clotting Risk of OCPs in a 40-Year-Old Daily Marijuana Smoker
The clotting risk associated with oral contraceptive pills (OCPs) is acceptable in a 40-year-old daily marijuana smoker who has never smoked cigarettes and has no other contraindications to OCP use. While there is a small increased risk of venous thromboembolism (VTE) with combined hormonal contraceptives, this risk is still low in absolute terms and is outweighed by the benefits of effective contraception in this specific patient profile.
Risk Assessment for Combined Hormonal Contraceptives (CHCs)
Baseline Risk Factors
- Age: At 40 years, the patient is approaching the upper age limit for CHC use but is still within acceptable range
- Marijuana use: Daily marijuana smoking has not been specifically identified as an independent risk factor for thrombosis in contraceptive guidelines
- No cigarette smoking: Importantly, this patient has never smoked cigarettes, which is a significant distinction
Thrombosis Risk Data
- The baseline risk of VTE in non-pregnant, non-OCP users is 1-5 per 10,000 woman-years 1
- Users of combined OCPs have a VTE risk of 3-9 per 10,000 woman-years 1
- This represents a small absolute increase in risk, though the relative risk is increased 2-3 fold
Relevant Guidelines
The WHO Medical Eligibility Criteria and CDC guidelines classify contraceptive use based on medical conditions:
- Category 1: No restrictions
- Category 2: Benefits generally outweigh risks
- Category 3: Risks usually outweigh benefits
- Category 4: Unacceptable health risk
For this patient:
- Cigarette smoking at age ≥35 years would be Category 3-4 (depending on number of cigarettes) 1, 2
- However, marijuana smoking is not specifically categorized in these guidelines
- With no other risk factors, this 40-year-old would likely fall under Category 2
Progestin-Only Options
If there are any concerns about thrombosis risk:
- Progestin-only pills (POPs) have not been shown to increase thrombosis risk (RR 1.02,95% CI 0.72-1.44 for stroke risk) 2
- POPs have a failure rate of approximately 0.5% in the first year with perfect use 2
- Long-acting reversible contraceptives like levonorgestrel IUDs have >99% effectiveness with minimal thrombosis risk 2
Important Considerations
Monitoring Recommendations
- Blood pressure should be measured before initiating OCPs and monitored periodically
- Women who have their blood pressure measured before OCP use have 2-2.5 fold decreased risk of myocardial infarction and ischemic stroke 3
Risk Perspective
- The absolute risk of VTE with OCPs (3-9/10,000 woman-years) is still lower than the risk during pregnancy (5-20/10,000 woman-years) 1
- For healthy non-smoking women, the small magnitude of blood pressure increase with OCP use is unlikely to be clinically significant 1
Marijuana vs. Cigarette Smoking
- While cigarette smoking significantly increases thrombosis risk with OCPs, there is no equivalent evidence for marijuana
- The contraindication for cigarette smokers aged ≥35 years is specific to tobacco, not cannabis 1
Recommendation Algorithm
Assess for additional risk factors:
- Hypertension
- Personal or family history of VTE
- Thrombophilia
- Obesity
- Migraine with aura
If no additional risk factors are present:
- Low-dose combined OCPs (containing ≤35 μg ethinyl estradiol) are acceptable
- Consider starting with a 30-35 μg ethinyl estradiol formulation with levonorgestrel or norgestimate 1
If any additional risk factors are identified:
- Switch to progestin-only methods (POP, IUD, implant)
- These methods have no demonstrated increased risk of thrombosis 2
Monitoring plan:
- Check blood pressure at initiation and follow-up
- Schedule follow-up within 1-3 months to assess for adverse effects 1
- Educate on signs/symptoms of VTE (leg pain/swelling, chest pain, shortness of breath)
The absence of cigarette smoking history and other contraindications makes this patient a reasonable candidate for combined OCPs despite her age and marijuana use, though progestin-only methods could be considered if there are any concerns about thrombosis risk.