Prescription medication · Selective Estrogen Receptor Modulator (SERM)

tamoxifen

Also sold as Nolvadex. This medicine is used to treat breast cancer that has spread in adults.

Data updated 2026-05-15

2,638
FDA reports
10
InteractionsSeveral interactions
$0.12
Generic price (NADAC)

What the data shows

tamoxifen (Nolvadex) is a prescription Selective Estrogen Receptor Modulator (SERM), with 2,638 FDA adverse-event reports on file, with 10 documented drug interactions.

Reporting volume reflects how widely a drug is used and studied, not how dangerous it is, a FAERS report documents a temporal association, never proof of cause.

tamoxifen (Nolvadex) is a prescription Selective Estrogen Receptor Modulator (SERM). This medicine is used to treat breast cancer that has spread in adults.

Tamoxifen (Soltamox) is a medicine that can treat breast cancer. It can also lower the chance of getting breast cancer in some people.

Verify with FDA → · CMS NADAC pricing →

Drug Pricing (NADAC)

Generic Price

$0.12/unit

Generic Available

Yes (4 manufacturers)

Pricing data from NADAC (CMS), effective December 18, 2024. Compare all drug costs →

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What it does

This medicine is used to treat breast cancer that has spread in adults.

Common side effects

Hot flashes, Mood changes, Vaginal discharge

Key warnings

Tamoxifen can cause serious and life-threatening problems, including cancer of the uterus, stroke, and blood clots in the lungs.

The sections below are summarized in plain English from tamoxifen's FDA-approved prescribing information. They describe what the official label says, and are not personal medical advice.

How It Works

Tamoxifen belongs to a class of drugs called Selective Estrogen Receptor Modulators (SERMs). It works by blocking the effects of estrogen in breast tissue. This can help to stop the growth of breast cancer cells.

Side Effects (from patient reports)

Based on 2,638 FDA adverse event reports.

Most-reported reactions

Adverse reactions in FAERS for tamoxifen, by number of reports

reports

What this shows Bars show how often each reaction was reported, not how likely it is to happen, a report records a temporal association, never proof that the drug caused it.

Source FDA Adverse Event Reporting System (FAERS)

Serious Warnings

Tamoxifen can cause serious and life-threatening problems, including cancer of the uterus, stroke, and blood clots in the lungs. Some cases have been fatal. Talk to your doctor about the risks and benefits of taking tamoxifen, especially if you are at high risk for breast cancer or have DCIS. For most people already diagnosed with breast cancer, the benefits of tamoxifen outweigh the risks.

Known Drug Interactions

major warfarin

( 7.1 ) Warfarin: Do not use in patients taking tamoxifen for DCIS and for reduction in breast cancer incidence in women at high risk. Warfarin A marked increase in anticoagulant effect may occur when tamoxifen is used in combination with warfarin. Closely monitor coagulation indices in patients who are taking tamoxifen for either the treatment of metastatic breast cancer or as adjuvant therapy who require concomitant use of warfarin [see Contraindications (4) ] .

Mechanism: Tamoxifen increases the blood-thinning effects of warfarin, which can lead to a much higher risk of dangerous bleeding.

major anastrozole

7 DRUG INTERACTIONS Tamoxifen: Do not use in combination with anastrozole. No additional benefit seen over tamoxifen monotherapy ( 7.1 , 14.1 ). 7.1 Tamoxifen Co-administration of anastrozole and tamoxifen in breast cancer patients reduced anastrozole plasma concentration by 27%.

Mechanism: Tamoxifen lowers the amount of anastrozole in your blood, which may make the treatment less effective against cancer. Research also shows that taking both drugs together provides no extra benefit compared to taking just one.

moderate letrozole

7 DRUG INTERACTIONS Anastrozole and letrozole: Should not be used in combination with tamoxifen. Letrozole The concomitant use of letrozole with tamoxifen is not recommended because the efficacy of the combination in the adjuvant treatment of breast cancer has not been established. Tamoxifen reduced the plasma concentration of letrozole by 38% when these drugs were co-administered [see Clinical Pharmacology (12.3) ].

Mechanism: Tamoxifen lowers the amount of letrozole in your blood, and it is not known if taking both together helps treat cancer effectively.

minor bupropion

Drugs that require metabolic activation by CYP2D6 to be effective (e.g., tamoxifen), theoretically could have reduced efficacy when administered concomitantly with inhibitors of CYP2D6 such as bupropion.

Mechanism: Bupropion prevents tamoxifen from being changed into its active form, which could make the tamoxifen less effective at treating cancer.

minor desvenlafaxine

Examples desipramine, atomoxetine, dextromethorphan, metoprolol, nebivolol, perphenazine, tolterodine 7.2 Drugs Having No Clinically Important Interactions with PRISTIQ Based on pharmacokinetic studies, no dosage adjustment is required for drugs that are mainly metabolized by CYP3A4 (e.g., midazolam), or for drugs that are metabolized by both CYP2D6 and CYP3A4 (e.g., tamoxifen, aripiprazole), when administered concomitantly with PRISTIQ [see Clinical Pharmacology (12.3) ].

Mechanism: Desvenlafaxine does not change the way the body breaks down tamoxifen.

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This is a plain-language summary of FDA-label interaction records and does not provide individual medication-combination directions.

Common Questions

What should I do if I experience abnormal vaginal bleeding?
Tell your doctor right away if you have any abnormal vaginal bleeding.
Can I take anastrozole or letrozole with tamoxifen?
No, you should not take anastrozole or letrozole with tamoxifen.
What should I do if I am taking warfarin?
You should not take tamoxifen if you are taking warfarin for DCIS or to reduce breast cancer risk.
How long should I take tamoxifen?
The usual duration is 5 to 10 years, as directed by your doctor.
What are the signs of a blood clot?
Signs of a blood clot include pain, swelling, warmth, redness, or shortness of breath. Seek immediate medical attention if you experience these.
Can tamoxifen affect my liver?
Yes, tamoxifen can affect your liver. Your doctor will perform periodic liver function tests.
What if I am already taking other medications?
Tell your doctor about all the medicines you take, including prescription and over-the-counter medicines, vitamins, and herbal supplements.
How will I know if the medicine is working?
Your doctor will monitor your condition to see if the medicine is working.
What should I do if I experience hot flashes?
Hot flashes are a common side effect. Talk to your doctor about ways to manage them.
Is there anything else I should avoid while taking tamoxifen?
Avoid strong CYP3A4 inducers like rifampin, as they can reduce the effectiveness of tamoxifen.
What are the common side effects of tamoxifen?
The registry lists Hot flashes, Mood changes, Vaginal discharge, Vaginal bleeding, Nausea among the most-reported FAERS reaction terms for tamoxifen. The compiled record contains 2,638 FDA adverse-event reports. These counts are not an individual symptom assessment.
Does tamoxifen interact with other medications?
The registry has 10 documented interaction rows for tamoxifen. Notable source-record pairings include warfarin, anastrozole, letrozole. These rows are not a complete medication review.
What drug class is tamoxifen?
tamoxifen belongs to the Selective Estrogen Receptor Modulator (SERM) drug class. It requires a prescription (Rx). This medicine is used to treat breast cancer that has spread in adults.
What pregnancy or breastfeeding source fields are listed for tamoxifen?
The FDA label for tamoxifen contains product-specific pregnancy or breastfeeding language. PlainMeds does not apply that source text to an individual.

Related Medications in Selective Estrogen Receptor Modulator (SERM)

Other drugs grouped near tamoxifen - same-class peers and common alternatives.

abiraterone

Zytiga

Abiraterone (Zytiga) is a medicine used with prednisone to treat prostate cancer that has spread.

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anastrozole

Arimidex

Anastrozole is a medicine used to treat breast cancer in women after menopause.

Compare with tamoxifen →

bazedoxifene/conjugated estrogens

Duavee

Duavee is a combination medicine containing estrogen and a drug that blocks estrogen in some parts of the body.

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cabergoline

Dostinex

Cabergoline is a medicine that helps lower the amount of prolactin in your body.

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clomiphene

Clomid, Serophene

Clomiphene citrate is a medicine that helps women ovulate.

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What the FDA Data Shows for tamoxifen

The FDA label for tamoxifen (sold under brand names such as Nolvadex) classifies it as a prescription-only medication in the Selective Estrogen Receptor Modulator (SERM) class. This medicine is used to treat breast cancer that has spread in adults. Official labeling lists 6 commonly reported side effects, including Hot flashes, Mood changes, Vaginal discharge.

Post-market surveillance from the FDA Adverse Event Reporting System (FAERS) captures real-world experience. For this drug, FAERS contains 2,638 voluntary reports. The database also lists 10 documented drug interactions derived from FDA labeling, with the top-flagged interaction rated major severity. NADAC pricing from CMS shows a generic unit cost of $0.12.

Report counts do not establish causation, a FAERS entry documents a temporal association, not proof that the drug produced the outcome. Widely prescribed medications naturally accumulate more reports than niche therapies, so raw totals must be interpreted alongside total exposure. Shortage status, recall history, and patent information are separate source-record fields. This page is a public FDA/CMS registry and does not provide medical, treatment, substitution, or medication-change directions.

Data Sources

Drug labeling: FDA Drug Labels (SPL/DailyMed). Adverse events: FDA Adverse Event Reporting System (FAERS). Pricing: CMS National Average Drug Acquisition Cost (NADAC).

FAERS reports are voluntary and do not establish causation. Drug interactions are derived from FDA labeling and clinical references. This registry does not provide medication decisions.

Last updated: November 29, 2021

PlainMeds is rendered directly from FDA openFDA/FAERS extracts, DailyMed labels, and CMS drug-pricing files, no number is typed in by an editor. FAERS counts, recalls, shortages, and price figures on this page are queried live from those federal extracts. See our editorial standards & corrections policy, the methodology behind these numbers, or report a data error. Data current as of 2026-05-15. Primary sources: openFDA / FAERS, DailyMed and CMS Part B ASP.

Read our methodology - how this data is sourced, computed, and verified.

Data currency: FDA FAERS adverse-event reports through 2025, CMS NADAC acquisition-cost pricing effective December 2024, compiled from the source snapshot dated . See our methodology for per-source dates and refresh cadence. Spot a figure that looks wrong? Report a data issue.

All federal data sources used on this page