Interaction Between Famotidine and Adderall
There is no clinically significant interaction between famotidine and Adderall (amphetamine and dextroamphetamine), and these medications can be safely used together.
Mechanism and Evidence
Famotidine is an H2-receptor antagonist that works by blocking histamine receptors in the stomach to reduce acid production. Unlike older H2-blockers like cimetidine, famotidine has a notable lack of drug interactions because:
- It does not interact with the cytochrome P450 enzyme system that metabolizes many medications 1
- It is approximately 8 times more potent than ranitidine and 40 times more potent than cimetidine, allowing for effective acid suppression at lower doses 2
- It has been extensively studied and shown to have minimal to no effect on the metabolism of various drugs 1
Adderall (amphetamine and dextroamphetamine) is primarily metabolized through different pathways than those affected by famotidine, which explains the lack of interaction.
Clinical Implications
When considering the use of these medications together:
- No dosage adjustments are needed when taking both medications
- There is no evidence of decreased efficacy of either medication when used concurrently
- No special monitoring is required beyond the standard monitoring recommended for each medication individually
Important Considerations for Each Medication
Famotidine
- Famotidine may affect the absorption rate (but not the extent) of certain medications by increasing gastric pH 3
- It has a longer duration of action than other H2-blockers like ranitidine or cimetidine 2
- Side effects are rare (0.43% in post-marketing studies) and may include headache, dizziness, constipation, or diarrhea 2
Adderall (Amphetamine/Dextroamphetamine)
- Typical starting dose is 5-10 mg daily, with titration up to a maximum of 50 mg daily based on symptom control and side effects 4
- Contraindicated in patients with advanced cardiovascular disease, high blood pressure, hyperthyroidism, glaucoma, agitation, history of substance abuse, or psychosis/mania 4
- Should not be combined with MAO inhibitors due to risk of hypertensive crisis 5
Special Populations
For pregnant patients:
- Amphetamines do not appear to be associated with major congenital malformations but may have a small increased risk for preeclampsia and preterm birth when used in the second half of pregnancy 5
For breastfeeding patients:
- Adderall is classified as L3 (moderately safe) during breastfeeding
- Monitor breastfed infants for irritability, insomnia, and feeding difficulties 5
Alternative Considerations
If there are concerns about using either medication:
- For ADHD: Non-stimulant options include atomoxetine, bupropion, or viloxazine
- For acid suppression: Proton pump inhibitors can be considered, though they have more potential drug interactions than famotidine
The evidence clearly shows that famotidine is one of the safest H2-blockers regarding drug interactions, making it an appropriate choice for patients taking multiple medications, including stimulants like Adderall.