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Tamoxifen

Tamoxifen is a drug with antitumor action belonging to the class of selective estrogen receptor modulators (SERM).

Tamoxifen - Chemical Structure

It is part of the list of essential drugs compiled by the World Health Organization (WHO), a list which lists all the drugs that must be present in a basic health system.

Indications

For what it uses

The use of tamoxifen is indicated for the treatment of breast cancer and for the prevention of recurrences.

Warnings

Tamoxifen should be administered with caution in patients with a decrease in the number of white blood cells (leucopenia) and with a decrease in the number of platelets (thrombocytopenia). Therefore, regular blood tests should be performed.

Tamoxifen can cause cataracts, so eye checks must be performed.

As tamoxifen can cause alterations - even serious - of the uterus, regular gynecological checks should be performed.

If the following symptoms appear following tamoxifen therapy, you should immediately inform your doctor:

  • Numbness of the face, weakness of arms or legs, problems with speech or vision, because they could indicate a cerebral stroke;
  • Chest pain or dyspnea, could be symptoms of pulmonary embolism;
  • Abdominal pain or abnormal vaginal bleeding that could indicate a possible cancer of the uterus;
  • Cough and dyspnea that could be symptoms of interstitial pneumonia.

Patients should inform their doctor if they have a history of stroke, thromboembolic disease or uterine cancer.

Tamoxifen can cause vision problems and drowsiness, so caution should be exercised in the event of driving and / or operating machinery.

For those who play sports, the use of the drug without therapeutic necessity is doping and - even at therapeutic doses - can determine positivity to anti-doping tests.

Interactions

Co-administration of tamoxifen and the following drugs should be avoided, as it may reduce the therapeutic efficacy of tamoxifen itself:

  • Paroxetine and fluoxetine, antidepressant drugs;
  • Bupropion, a drug used for the treatment of depression and smoking cessation;
  • Quinidine, an antiarrhythmic drug;
  • Cinacalcet, a drug used to treat secondary hyperparathyroidism.

Tamoxifen may potentiate the activity of oral anticoagulants, such as - for example - warfarin .

Concomitant administration of tamoxifen and other anticancer drugs may increase the risk of developing thromboembolic episodes.

Concomitant administration of tamoxifen and drugs that reduce renal calcium excretion (such as, for example, thiazide diuretics ) may increase the risk of hypercalcaemia (increased levels of calcium in the bloodstream).

The concomitant use of tamoxifen and mitomycin (a cytotoxic antibiotic, ie toxic for cells) should be avoided, as it increases the risk of the onset of hemolytic uremic syndrome, anemia and thrombocytopenia.

Tamoxifen is metabolized in the liver by cytochrome P3A4, therefore the simultaneous intake of tamoxifen and drugs capable of inhibiting this enzyme should be avoided.

Side effects

Tamoxifen can induce many side effects. Each individual responds to therapy differently depending on their sensitivity to the drug, therefore it is not said that the adverse effects occur all with the same intensity in each patient.

Listed below are the main side effects that may occur following tamoxifen therapy.

Carcinogenicity

The use of tamoxifen may promote the occurrence of secondary uterine tumors. In particular, endometrial adenocarcinoma and uterine sarcoma may occur.

Furthermore, cases of uterine fibroids, endometriosis and other endometrial changes, including polyps and hyperplasia, have been reported.

Respiratory disorders

Tamoxifen therapy may cause interstitial pneumonia with symptoms such as dyspnea and cough.

Reproductive system disorders

During treatment with tamoxifen menstrual disorders, amenorrhea (absence of menstruation), vaginal bleeding, vulvar itching (around the vagina), vaginal discharge and ovarian cysts may occur.

Vascular pathologies

Tamoxifen therapy can cause increased blood clotting, pulmonary thromboembolism, deep vein thrombosis and stroke. Some cases have proved fatal.

In addition, inflammation of blood vessels with cutaneous manifestations may occur.

Gastrointestinal disorders

Tamoxifen therapy can cause nausea, vomiting, constipation and abdominal pain. Furthermore, the drug can promote the appearance of anorexia.

Bone marrow disorders

Tamoxifen can affect the production of blood cells carried out by the bone marrow, which causes:

  • Anemia (decrease in hemoglobin blood levels), the main symptom of the onset of anemia is the feeling of physical exhaustion;
  • Leukopenia (decreased white blood cell levels), with increased susceptibility to contraction of infections;
  • Plateletopenia (decrease in the number of platelets), this leads to the appearance of bruising and abnormal bleeding with an increased risk of bleeding.

Eye disorders

Treatment with tamoxifen can cause visual disturbances, blurred vision, loss of visual acuity, cataracts, corneal changes and retinal pathologies.

Hepatobiliary disorders

Tamoxifen can cause changes in the levels of liver enzymes in the bloodstream and promote the onset of jaundice.

Other side effects

Other side effects that may occur following treatment with tamoxifen are:

  • Allergic reactions in sensitive subjects;
  • Pain and increased size of the area affected by the tumor, this happens especially at the beginning of the treatment;
  • Hot flashes;
  • Skin reactions;
  • Bullous eruptions;
  • Stevens-Johnson syndrome (a more severe variant of polymorphic erythema);
  • Alopecia;
  • Water retention that can cause ankle swelling;
  • Hypertriglyceridemia, sometimes associated with pancreatitis;
  • Hypercalcemia that can manifest itself with symptoms, such as excessive nausea, vomiting and thirst;
  • Drowsiness;
  • Fatigue;
  • Fatigue;
  • Headache;
  • Dizziness;
  • dizziness;
  • Depression;
  • Confusion;
  • Muscle cramps;
  • Bone pain.

Overdose

If you suspect you have overdosed, you should contact a doctor immediately and contact your nearest hospital.

Action mechanism

Tamoxifen is a selective estrogen receptor modulator (SERM).

Some forms of breast cancer need estrogen (the main female sex hormones) to survive. The cells forming these tumors have estrogen receptors (ER) on their own membranes. Hormones, therefore, bind to these receptors in such a way as to perform the biological functions necessary for the survival of the aforementioned tumor cells.

Tamoxifen works by binding to ERs instead of estrogens. In doing so, cancer cells are deprived of the action of these essential elements and die.

Mode of Use - Posology

Tamoxifen is available for oral administration in the form of 10 mg and 20 mg tablets.

The dosage of tamoxifen must be established by the doctor based on the patient's clinical picture.

In any case, the dose of tamoxifen usually used is 20 mg a day, to be administered in two divided doses or in a single daily dose. The dose can be increased up to 40 mg of active ingredient per day.

These dosages can also be used in elderly patients.

Pregnancy and breastfeeding

Since tamoxifen can cause serious harm to the fetus, pregnant women should not take the drug.

It is not known whether tamoxifen is excreted in breast milk, therefore breast-feeding mothers should not start treatment with the drug.

Contraindications

The use of tamoxifen is contraindicated in the following cases:

  • Known hypersensitivity to tamoxifen;
  • As a preventive therapy in patients at high risk of developing breast cancer;
  • In patients with ductal carcinoma in situ (an initial form of breast cancer, also called precancerous);
  • In patients who require concurrent anticoagulant therapy;
  • In patients with a history of deep vein thrombosis;
  • In patients with a history of pulmonary embolism;
  • In children and adolescents;
  • Pregnant;
  • During breastfeeding.

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