TamoxifenTamoxifen Citrate

About Tamoxifen

Tamoxifen is an estrogen agonist/antagonist: it competes with estrogen for the estrogen receptor, which can slow estrogen-driven growth in breast tissue. The labels cover metastatic breast cancer in women and men; adjuvant treatment of early-stage estrogen receptor-positive breast cancer, which also lowers the chance of cancer in the other breast; DCIS after surgery and radiation; and lowering the chance of breast cancer in women at high risk. The usual dose is 20 mg a day: for 5 years after DCIS or for risk reduction, and as adjuvant treatment for 5 years on the Nolvadex tablet label or 5 to 10 years on the newer Soltamox label; in metastatic disease 20 to 40 mg a day is used, with doses above 20 mg split between morning and evening. Safety and effectiveness in children have not been established.

The boxed warning applies to women with DCIS and women at high risk: uterine cancers (endometrial cancer and uterine sarcoma), stroke and pulmonary embolism have occurred, some fatal, so benefits and risks are discussed first; for most people already diagnosed with breast cancer, the label says the benefits outweigh the risks. In those two settings it is not taken with warfarin-type anticoagulants or after a deep vein thrombosis or pulmonary embolism. Abnormal vaginal bleeding is checked promptly, and yearly gynecologic exams are advised. It also raises the risk of blood clots, more so with chemotherapy, and can cause cataracts and other eye changes, liver problems, low platelets, and high calcium when cancer has spread to bone, so blood counts and liver tests are checked periodically. Hot flashes, mood changes, vaginal discharge and bleeding, nausea and fluid retention are the most common side effects.

Tamoxifen can harm a developing baby, so pregnancy is ruled out before starting, and effective non-hormonal birth control is used during treatment and for 2 months after the last dose; breastfeeding is avoided during treatment and for 3 months after. Strong CYP3A4 inducers such as rifampin lower its levels and should not be used with it, letrozole is not recommended with it, and anastrozole is avoided. For strong CYP2D6 inhibitors such as paroxetine, the label says the effect on how well tamoxifen works is not well established: some studies found it reduced, others did not.

Taking Tamoxifen

How to take it

Once or twice a day as prescribed, with or without food, at about the same time each day. Swallow tablets whole; do not split, chew or crush them. Measure the oral solution with the dosing cup provided, not a kitchen spoon.

If you miss a dose

Take it as soon as you remember, unless it is almost time for the next dose; then skip the missed dose. Do not take a double dose.

Storage

Tablets: at room temperature in a tightly closed, light-resistant container, away from heat and moisture (not in the bathroom). Solution: at room temperature in its original bottle, never refrigerated or frozen, and thrown away 3 months after first opening.

Interactions to know about

Warfarin’s effect can rise sharply: it is not used with tamoxifen after DCIS or for risk reduction, and otherwise clotting tests are watched closely. Rifampin and other strong CYP3A4 inducers lower tamoxifen levels and should not be used with it. Letrozole and anastrozole are not used with it. Use non-hormonal birth control, and tell the prescriber if you take paroxetine or another medicine that blocks CYP2D6.

This summarizes the official prescribing information. Your prescriber’s and pharmacist’s instructions, and the leaflet that comes with your medicine, take priority.

Why the cash price for Tamoxifen differs from pharmacy to pharmacy

Tamoxifen tablets are an old generic, so a tablet quote is mostly the dispensing fee and markup, and whether it is on a pharmacy’s flat-price generic list varies. Treatment usually runs for years, so a ninety-day fill spreads one fee over three months.

Soltamox has no generic, so it is priced as a brand, and a pharmacy may need to order it; references differ on whether it is still marketed. The tablet and the liquid are different dosage forms, so a pharmacy fills the form written, and a dose written as two 10 mg tablets instead of one 20 mg tablet raises the count.

Ways to pay less for Tamoxifen without insurance

• Ask for generic tablets, and make sure the prescription allows substitution.
• Ask for a ninety-day supply, since treatment usually lasts years, and compare more than one pharmacy.
• If your dose is 20 mg, check that it is written as one 20 mg tablet rather than two 10 mg tablets.
• If the liquid was prescribed and you can swallow tablets, ask the prescriber whether tablets would suit you; for Soltamox, ask the maker whether a savings program applies to someone paying cash.
• Upload the prescription to Script Unlock so licensed pharmacies can quote their cash price. You pay the pharmacy directly.

Questions to ask your pharmacist about Tamoxifen

1. 1.Do any of my medicines, such as my antidepressant, affect how well tamoxifen works?
2. 2.Which signs of a blood clot, stroke or uterine problem mean I should get help right away?
3. 3.Which birth control can I use, and for how long after my last dose?
4. 4.Is it safe with my blood thinner?

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