Can Ramipril and Synthroid Be Taken at the Same Time?
Yes, ramipril and Synthroid (levothyroxine) can be taken at the same time without significant drug-drug interactions, though monitoring of thyroid function is recommended when starting or stopping either medication.
No Direct Pharmacokinetic Interaction
- There is no documented direct interaction between ramipril (an ACE inhibitor) and levothyroxine in the available evidence 1
- ACE inhibitors like ramipril are not listed among medications that significantly affect levothyroxine metabolism or absorption 1
- The cardiovascular guidelines extensively discuss ramipril use without mentioning thyroid medication interactions as a concern 1
Important Monitoring Considerations
Monitor thyroid function (serum TSH) when initiating or changing doses of either medication:
- Levothyroxine has a narrow therapeutic index, requiring careful dose titration to avoid both subclinical hypothyroidism (underdosing) and subclinical hyperthyroidism (overdosing) 2
- Some tyrosine kinase inhibitors have been associated with hypothyroidism requiring levothyroxine dose adjustments, though this mechanism is unclear and not applicable to ramipril 1
- When medications are used together that could theoretically affect thyroid status, TSH monitoring is prudent clinical practice 1
Clinical Context for Combined Use
These medications are commonly prescribed together for patients with multiple comorbidities:
- Ramipril is indicated for hypertension, heart failure, post-myocardial infarction, and cardiovascular risk reduction 1, 3
- Levothyroxine is the standard treatment for hypothyroidism, which frequently coexists with cardiovascular disease 2, 4
- The combination is clinically appropriate when both conditions require treatment 1, 2
Practical Administration Recommendations
For optimal absorption and monitoring:
- Levothyroxine should be taken on an empty stomach, typically 30-60 minutes before breakfast for consistent absorption 2
- Ramipril can be taken once daily, either morning or evening, with or without food 5
- These medications can be taken at the same time in the morning without concern for interaction 5
- Check TSH levels 4-6 weeks after starting either medication or changing doses to ensure therapeutic targets are maintained 2, 6
Key Caveat: Rifampin Exception
The only significant interaction with levothyroxine metabolism involves rifampin (not ramipril):
- Rifampin induces hepatic enzymes and significantly increases levothyroxine metabolism, requiring dose increases of 50-100% in many patients 1, 6
- This is completely unrelated to ramipril, which does not induce hepatic enzymes 1
- Do not confuse ramipril with rifampin—they are entirely different drug classes with different interaction profiles 1, 3