Inclusion Criteria:

• Female patients must have histologically or cytologically indicated breast cancer (stages I, II, III) eligible for adjuvant anthracycline chemotherapy [FEC100 or AC-Taxol(paclitaxel) every 21 days.
• HER2 negative or HER2 positive breast cancer by immunohistochemistry (IHC3+) and/or fluorescent in-situ hybridization.
• Eastern cooperative oncology group (ECOG) performance status = 0, 1, 2
• Age ≥ 18 years old.
• Ability to understand and the willingness to sign a written informed consent document.
• The effects of L-carnitine on the developing human fetus at the recommended therapeutic dose are unknown. For this reason, women of child-bearing potential must agree to use adequate contraception prior to study entry and for the duration of study participation. Should a woman become pregnant or suspect she is pregnant while participating in this study, she should inform her treating physician immediately.

Exclusion Criteria:

• Patients with evidence of metastatic breast cancer.
• Resting LV ejection fraction < 50%.
• Patients having received previous anthracycline therapy or contraindication to anthracycline.
• Patients having a contraindication to L-carnitine therapy
• Dexrazoxane therapy at the time of enrollment.

• Patients with abnormal baseline bloodwork:

  • hemoglobin ≤ 100 mg/L
  • platelets ≤ 100 x 10^9/L
  • white blood cells ≤ 4 x 10^9/L
  • creatinine, AST, ALT, bilirubin > 1.5 x the upper normal limits
• Participation in another randomized clinical trial.
• Patients having significant cardiac disease (previous myocardial infarction, congestive heart failure, or hemodynamically significant valvular heart disease) that would limit compliance with study requirements.
• Patients taking medication that may affect LV function (b-blockers, amiodarone, ACE-inhibitors, calcium channel blockers, or digoxin).
• Patients with symptoms of heart failure.
• Patients unable to participate in a study requiring long term follow up.
• Pregnant or lactating women.