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Drug Interaction Report

This report displays the potential drug interactions for the following 3 drugs:

  • fluoxetine
  • amlodipine
  • Levothyrox (levothyroxine)

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Interactions between your drugs


FLUoxetine amLODIPine

Applies to: fluoxetine, amlodipine

MONITOR: Coadministration of fluoxetine with calcium channel blockers may increase their plasma concentrations and the risk of side effects. The mechanism is reduced clearance of the calcium channel blocker due to inhibition of CYP450 3A4-mediated metabolism by fluoxetine. Reports exist for nifedipine, nimodipine, and verapamil. Theoretically, the interaction may also occur with other calcium channel blockers that are CYP450 3A4 substrates.

MANAGEMENT: Monitoring of clinical response and tolerance, including blood pressure, is recommended if fluoxetine is used in combination with calcium channel blockers that are metabolized by CYP450 3A4. Dose reductions may be considered, if necessary. Patients should be advised to seek medical attention if they experience edema or swelling of the lower extremities; sudden, unexplained weight gain; difficulty breathing; chest pain or tightness; or hypotension as indicated by dizziness, fainting, or orthostasis.


  1. Canadian Pharmacists Association "e-CPS. Available from: URL:"
  2. "Product Information. Nimotop (nimodipine)." Bayer, West Haven, CT.
  3. Cerner Multum, Inc. "Australian Product Information." O 0
  4. "Product Information. Adalat (nifedipine)." Bayer, West Haven, CT.
  5. Cerner Multum, Inc. "UK Summary of Product Characteristics." O 0
View all 5 references

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FLUoxetine levothyroxine

Applies to: fluoxetine, Levothyrox (levothyroxine)

Case reports suggest that thyroid hormone supplementation may enhance the therapeutic effects of fluoxetine in the treatment of major depression. The mechanism is unknown.


  1. Agid O, Shalev AY, Lerer B "Triiodothyronine augmentation of selective serotonin reuptake inhibitors in posttraumatic stress disorder." J Clin Psychiatry 62 (2001): 169-73
  2. Gupta S, Masand P, Tanquary JF "Thyroid hormone supplementation of fluoxetine in the treatment of major depression." Br J Psychiatry 159 (1991): 866-7

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No other interactions were found between your selected drugs. This does not necessarily mean no other interactions exist. Always consult your healthcare provider.

Drug and food interactions


FLUoxetine food

Applies to: fluoxetine

GENERALLY AVOID: Alcohol may potentiate some of the pharmacologic effects of CNS-active agents. Use in combination may result in additive central nervous system depression and/or impairment of judgment, thinking, and psychomotor skills.

MANAGEMENT: Patients receiving CNS-active agents should be warned of this interaction and advised to avoid or limit consumption of alcohol. Ambulatory patients should be counseled to avoid hazardous activities requiring complete mental alertness and motor coordination until they know how these agents affect them, and to notify their physician if they experience excessive or prolonged CNS effects that interfere with their normal activities.


  1. "Product Information. Fycompa (perampanel)." Eisai Inc, Teaneck, NJ.
  2. Gilman AG, Rall TW, Nies AS, Taylor P, eds. "Goodman and Gilman's the Pharmacological Basis of Therapeutics. 8th ed." New York, NY: Pergamon Press Inc. (1990):
  3. Warrington SJ, Ankier SI, Turner P "Evaluation of possible interactions between ethanol and trazodone or amitriptyline." Neuropsychobiology 15 (1986): 31-7
  4. "Product Information. Rexulti (brexpiprazole)." Otsuka American Pharmaceuticals Inc, Rockville, MD.
View all 4 references

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levothyroxine food

Applies to: Levothyrox (levothyroxine)

ADJUST DOSING INTERVAL: Consumption of certain foods as well as the timing of meals relative to dosing may affect the absorption of T4 thyroid hormone (i.e., levothyroxine). T4 absorption is increased by fasting and decreased by foods such as soybean flour (e.g., infant formula), cotton seed meal, walnuts, dietary fiber, calcium, and calcium fortified juices.

MANAGEMENT: Preparations containing T4 thyroid hormone should be administered on a consistent schedule with regard to time of day and relation to meals so as to avoid large fluctuations in serum levels. Foods that may affect T4 absorption should be avoided within several hours of dosing if possible. When administered to patients receiving continuous enteral nutrition for more than 7 days, some experts recommend that the tube feeding should be interrupted for at least 1 hour before and 1 hour after the dose of levothyroxine is given and to monitor patients' thyroid function.


  1. "Product Information. Armour thyroid (thyroid desiccated)." Forest Pharmaceuticals, St. Louis, MO.
  2. Wohlt PD, Zheng L, Gunderson S, Balzar SA, Johnson BD, Fish JT "Recommendations for the use of medications with continuous enteral nutrition." Am J Health Syst Pharm 66 (2009): 1438-67
  3. "Product Information. Synthroid (levothyroxine)." Abbott Pharmaceutical, Abbott Park, IL.

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amLODIPine food

Applies to: amlodipine

The consumption of grapefruit juice may slightly increase plasma concentrations of amlodipine. The mechanism is inhibition of CYP450 3A4-mediated first-pass metabolism in the gut wall by certain compounds present in grapefruits. Data have been conflicting and the clinical significance is unknown. Monitoring for calcium channel blocker adverse effects (e.g., headache, hypotension, syncope, tachycardia, edema) is recommended.


  1. Kane GC, Lipsky JJ "Drug-grapefruit juice interactions." Mayo Clin Proc 75 (2000): 933-42
  2. Bailey DG, Malcolm J, Arnold O, Spence JD "Grapefruit juice-drug interactions." Br J Clin Pharmacol 46 (1998): 101-10
  3. Vincent J, Harris SI, Foulds G, Dogolo LC, Willavize S, Friedman HL "Lack of effect of grapefruit juice on the pharmacokinetics and pharmacodynamics of amlodipine." Br J Clin Pharmacol 50 (2000): 455-63
  4. Bailey DG, Arnold JMO, Spence JD "Grapefruit juice and drugs - how significant is the interaction." Clin Pharmacokinet 26 (1994): 91-8
  5. Josefsson M, Zackrisson AL, Ahlner J "Effect of grapefruit juice on the pharmacokinetics of amlodipine in healthy volunteers." Eur J Clin Pharmacol 51 (1996): 189-93
  6. Josefsson M, Ahlner J "Amlodipine and grapefruit juice." Br J Clin Pharmacol 53 (2002): 405; discussion 406
View all 6 references

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Therapeutic duplication warnings

No warnings were found for your selected drugs.

Therapeutic duplication warnings are only returned when drugs within the same group exceed the recommended therapeutic duplication maximum.

Drug Interaction Classification

These classifications are only a guideline. The relevance of a particular drug interaction to a specific individual is difficult to determine. Always consult your healthcare provider before starting or stopping any medication.
Major Highly clinically significant. Avoid combinations; the risk of the interaction outweighs the benefit.
Moderate Moderately clinically significant. Usually avoid combinations; use it only under special circumstances.
Minor Minimally clinically significant. Minimize risk; assess risk and consider an alternative drug, take steps to circumvent the interaction risk and/or institute a monitoring plan.
Unknown No interaction information available.

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

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