Tamoxifen 20 mg A Comprehensive Guide

Tamoxifen 20 mg, a selective estrogen receptor modulator (SERM), stands as a cornerstone in the treatment and prevention of breast cancer. Its mechanism of action revolves around blocking estrogen from binding to its receptors in breast tissue, effectively hindering the growth of estrogen-dependent tumors. Tamoxifen 20 mg is available in tablet form and is typically administered orally, with dosage varying depending on the patient’s condition and other factors.

This medication has revolutionized breast cancer management, offering hope to countless individuals. Its applications extend beyond breast cancer, encompassing the treatment of conditions like endometriosis and uterine fibroids. Understanding the intricacies of Tamoxifen 20 mg, from its dosage and administration to its potential side effects and interactions, is crucial for informed medical decisions and optimal patient outcomes.

Table of Contents

Tamoxifen 20 mg

Tamoxifen 20 mg is a medication used to treat and prevent certain types of breast cancer and to reduce the risk of breast cancer in women at high risk. It is also used to treat certain conditions related to estrogen levels, such as endometriosis and infertility.

Mechanism of Action

Tamoxifen 20 mg works by blocking the effects of estrogen in certain tissues of the body. Estrogen is a hormone that plays a role in the growth and development of breast tissue. Tamoxifen 20 mg acts as an anti-estrogen, preventing estrogen from binding to its receptors in breast cells. By blocking estrogen’s action, tamoxifen can help to slow or stop the growth of breast cancer cells.

Pharmaceutical Formulation

Tamoxifen 20 mg is available in tablet form. The tablets are typically taken once a day, with or without food.

Medical Applications

Tamoxifen 20 mg is a selective estrogen receptor modulator (SERM) with diverse medical applications, primarily in the management of breast cancer and the prevention of its development in high-risk individuals.

Breast Cancer Treatment

Tamoxifen 20 mg plays a crucial role in treating breast cancer, both as an adjuvant therapy after surgery and as a neoadjuvant therapy before surgery.

Adjuvant Therapy: Tamoxifen 20 mg is commonly prescribed after surgery to reduce the risk of breast cancer recurrence. It works by blocking estrogen receptors in breast cells, preventing the growth of cancer cells that are estrogen-dependent.
Neoadjuvant Therapy: In some cases, Tamoxifen 20 mg is used before surgery to shrink the tumor size, making it easier to remove surgically. This approach can improve surgical outcomes and potentially reduce the need for more aggressive treatments.

Breast Cancer Prevention

For women with a high risk of developing breast cancer, Tamoxifen 20 mg can be used to reduce this risk.

High-Risk Individuals: Women with a strong family history of breast cancer, genetic mutations like BRCA1 or BRCA2, or other risk factors may benefit from Tamoxifen 20 mg.
Risk Reduction: Studies have shown that Tamoxifen 20 mg can significantly reduce the risk of breast cancer in these high-risk individuals.

Other Potential Uses

While primarily known for its role in breast cancer, Tamoxifen 20 mg has shown promise in other medical applications.

Endometriosis: Tamoxifen 20 mg can help manage endometriosis, a condition where uterine tissue grows outside the uterus. It works by reducing estrogen levels, which can alleviate symptoms like pain and heavy bleeding.
Uterine Fibroids: Tamoxifen 20 mg may also be used to treat uterine fibroids, noncancerous growths in the uterus. It can reduce fibroid size and alleviate associated symptoms like heavy bleeding and pelvic pain.

Dosage and Administration

Tamoxifen 20 mg is typically administered orally, usually once daily. The specific dosage and administration schedule will vary depending on the patient’s condition and individual factors. It is important to consult with a healthcare professional to determine the appropriate dosage and administration schedule for each individual.

Dosage Recommendations

Dosage recommendations for Tamoxifen 20 mg vary depending on the specific medical condition being treated. Here are some general guidelines:

* Breast cancer: The usual dosage for the treatment of breast cancer is 20 mg once daily.
* Prevention of breast cancer: For women at high risk of developing breast cancer, the recommended dosage is 20 mg once daily.
* Endometriosis: The recommended dosage for the treatment of endometriosis is 20 mg once daily for up to 6 months.

Individualizing Dosage

The dosage of Tamoxifen 20 mg should be individualized based on factors such as:

* Age: Older patients may require lower dosages.
* Liver function: Patients with impaired liver function may require lower dosages.
* Other medical conditions: The presence of other medical conditions may necessitate dosage adjustments.

Routes of Administration

Tamoxifen 20 mg is typically administered orally. However, in some cases, it may be administered intravenously.

Oral administration is the most common route of administration for Tamoxifen 20 mg. The tablets are usually taken with a glass of water.

Intravenous administration is reserved for patients who cannot take Tamoxifen 20 mg orally.

Side Effects and Adverse Reactions

Tamoxifen 20 mg, like many medications, can cause side effects. These side effects can range from mild and manageable to severe and potentially life-threatening. Understanding the potential side effects and how to manage them is crucial for safe and effective treatment.

Common Side Effects

Common side effects of Tamoxifen 20 mg are usually mild and often resolve on their own or with simple management strategies.

Hot flashes: These are sudden feelings of warmth, often accompanied by sweating, that can occur in both men and women. They are caused by changes in hormone levels.
Nausea and vomiting: These side effects are often mild and may be relieved by eating smaller, more frequent meals and avoiding fatty foods.
Vaginal dryness: This can be managed with over-the-counter lubricants or vaginal moisturizers.
Hair thinning or loss: This is usually temporary and hair growth often returns after treatment is completed.
Weight gain: This can be influenced by changes in appetite and metabolism.
Joint pain: This is often mild and can be managed with over-the-counter pain relievers.
Mood swings: These can be due to hormonal fluctuations and may improve with time.

Serious Side Effects

While less common, Tamoxifen 20 mg can cause serious side effects. It is important to seek medical attention immediately if you experience any of these:

Blood clots: These can occur in the legs, lungs, or brain and can be life-threatening. Symptoms include chest pain, shortness of breath, leg swelling, and sudden confusion.
Stroke: This is a serious condition that occurs when blood flow to the brain is interrupted. Symptoms include sudden weakness, numbness, or paralysis on one side of the body, difficulty speaking, and vision problems.
Heart attack: This occurs when the heart muscle is deprived of oxygen. Symptoms include chest pain, shortness of breath, nausea, and sweating.
Uterine cancer: Tamoxifen 20 mg can increase the risk of uterine cancer, especially in women who have a family history of the disease.
Liver problems: These can be indicated by jaundice (yellowing of the skin and eyes), dark urine, and fatigue.
Eye problems: These can include cataracts, retinal detachment, and corneal ulcers.

Management Strategies, Tamoxifen 20 mg

Managing side effects of Tamoxifen 20 mg often involves lifestyle changes, over-the-counter medications, and in some cases, adjustments to the medication regimen.

Hot flashes: Wearing loose-fitting clothing, staying cool, and avoiding triggers like spicy foods can help.
Nausea and vomiting: Eating smaller, more frequent meals, avoiding fatty foods, and taking anti-nausea medications can help.
Vaginal dryness: Using over-the-counter lubricants or vaginal moisturizers can help.
Hair thinning or loss: This is usually temporary and hair growth often returns after treatment is completed.
Weight gain: Maintaining a healthy diet and exercise regimen can help manage weight gain.
Joint pain: Over-the-counter pain relievers can help manage joint pain.
Mood swings: Exercise, relaxation techniques, and talking to a therapist can help manage mood swings.

Reporting Side Effects

It is important to report any side effects you experience to your doctor, even if they seem minor. This allows your doctor to monitor your progress and adjust your treatment plan if necessary.

Drug Interactions

Tamoxifen 20 mg can interact with other medications, potentially affecting their efficacy or increasing the risk of side effects. Understanding these interactions is crucial for safe and effective treatment.

Clinically Significant Interactions

Clinically significant interactions with Tamoxifen 20 mg can lead to serious adverse effects. These interactions can be categorized into two main types: pharmacokinetic and pharmacodynamic.

Pharmacokinetic Interactions

Pharmacokinetic interactions involve alterations in the absorption, distribution, metabolism, or excretion of drugs. Tamoxifen 20 mg can be affected by these interactions, potentially leading to changes in its concentration in the body, influencing its effectiveness.

CYP3A4 Inhibitors: Tamoxifen 20 mg is metabolized by the enzyme CYP3A4. Drugs that inhibit CYP3A4, such as ketoconazole, erythromycin, and grapefruit juice, can increase tamoxifen levels in the blood, potentially leading to increased side effects.
CYP3A4 Inducers: Conversely, drugs that induce CYP3A4, such as rifampicin and phenytoin, can decrease tamoxifen levels, potentially reducing its efficacy.
P-Glycoprotein Inhibitors: Tamoxifen 20 mg is a substrate for P-glycoprotein, a transporter protein that removes drugs from the body. Drugs that inhibit P-glycoprotein, such as verapamil and quinidine, can increase tamoxifen levels by reducing its efflux from cells.

Pharmacodynamic Interactions

Pharmacodynamic interactions involve alterations in the effects of drugs at their target sites. Tamoxifen 20 mg can interact with other drugs at the same target sites, potentially leading to additive or antagonistic effects.

Anticoagulants: Tamoxifen 20 mg can enhance the anticoagulant effects of warfarin, increasing the risk of bleeding. This interaction is due to their shared target, the coagulation cascade.
Hormonal Medications: Tamoxifen 20 mg, an anti-estrogen, can interact with other hormonal medications, such as estrogen replacement therapy or oral contraceptives. These interactions can affect the efficacy of both drugs.

Less Severe Interactions

Less severe interactions with Tamoxifen 20 mg may not pose a significant risk but can still influence the effectiveness of the medication or lead to minor side effects.

Digoxin: Tamoxifen 20 mg can increase digoxin levels in the blood, potentially leading to digoxin toxicity. This interaction is thought to be due to reduced digoxin clearance by the kidneys.
Anticonvulsants: Some anticonvulsants, such as phenytoin and carbamazepine, can induce CYP3A4, potentially reducing tamoxifen levels. However, this interaction is less severe than that with strong CYP3A4 inducers.

Management of Drug Interactions

Managing drug interactions involving Tamoxifen 20 mg requires careful monitoring and potential adjustments to medication regimens.

Monitor for Side Effects: Closely monitor patients for signs and symptoms of adverse effects, especially when taking drugs that interact with Tamoxifen 20 mg.
Dosage Adjustments: Dosage adjustments may be necessary to optimize treatment outcomes and minimize adverse effects.
Alternative Medications: If possible, consider alternative medications with fewer interactions.
Consult with a Healthcare Professional: Always consult with a healthcare professional before taking any new medications, especially if you are already taking Tamoxifen 20 mg.

Contraindications and Precautions

Tamoxifen 20 mg, like any medication, has certain contraindications and precautions that healthcare professionals should be aware of before prescribing or administering it. This section will Artikel these contraindications and precautions, emphasizing the importance of patient counseling and education regarding Tamoxifen 20 mg use.

Absolute Contraindications

It is crucial to understand the absolute contraindications for Tamoxifen 20 mg use, as these conditions may increase the risk of serious adverse events.

Known hypersensitivity to tamoxifen or any of its ingredients. This includes a history of allergic reactions to tamoxifen or related drugs.
Pregnancy. Tamoxifen is a known teratogen, meaning it can cause birth defects.
Breastfeeding. Tamoxifen is excreted in breast milk and can potentially harm a nursing infant.

Precautions

While not absolute contraindications, there are specific precautions that should be taken when prescribing or administering Tamoxifen 20 mg. These precautions are designed to minimize the risk of adverse events and ensure the safe and effective use of the medication.

History of Thromboembolic Events: Tamoxifen has been associated with an increased risk of thromboembolic events, such as deep vein thrombosis (DVT) and pulmonary embolism (PE). Patients with a history of these events should be carefully monitored and may require additional preventative measures, such as anticoagulation therapy.
Liver Disease: Patients with severe liver disease should use Tamoxifen with caution, as the drug is primarily metabolized by the liver. Monitoring liver function is essential in these patients.
Endometrial Cancer: Tamoxifen can stimulate the growth of endometrial tissue, increasing the risk of endometrial cancer. Patients with a history of endometrial cancer or those at high risk should be closely monitored for any signs or symptoms of this condition.
Stroke: Some studies have suggested a potential association between Tamoxifen use and an increased risk of stroke. Patients with a history of stroke or other cerebrovascular disease should be carefully evaluated and monitored for any signs of neurological events.
Cataracts and Retinopathy: Tamoxifen can cause cataracts and retinopathy, although these events are relatively uncommon. Patients should be advised to undergo regular eye examinations, especially those with a history of eye problems.
Hormone-Sensitive Cancers: Tamoxifen is not recommended for patients with certain hormone-sensitive cancers, such as endometrial cancer or ovarian cancer. It can potentially stimulate the growth of these cancers.
Drug Interactions: Tamoxifen can interact with other medications, including certain antidepressants, anticonvulsants, and antibiotics. It is essential to inform healthcare professionals about all medications and supplements being taken before starting Tamoxifen therapy.
Patient Counseling and Education: Patient counseling and education are crucial to ensure the safe and effective use of Tamoxifen 20 mg. Patients should be informed about the potential benefits and risks of the medication, including the possibility of side effects, contraindications, and drug interactions.

Patient Counseling and Education

Patients should be counseled and educated about the following:

Purpose of Tamoxifen: Patients should understand why they are taking Tamoxifen and what it is intended to achieve.
Dosage and Administration: Patients should be instructed on the correct dosage and administration of Tamoxifen, including the frequency and timing of doses.
Potential Side Effects: Patients should be aware of the potential side effects of Tamoxifen, including common and serious adverse events. They should be encouraged to report any unusual symptoms to their healthcare provider.
Contraindications: Patients should be informed about the contraindications for Tamoxifen use, including pregnancy, breastfeeding, and hypersensitivity to the drug.
Drug Interactions: Patients should be advised to inform their healthcare provider about all medications and supplements they are taking, including over-the-counter drugs, herbal remedies, and vitamins. This will help to identify potential drug interactions that could affect the effectiveness or safety of Tamoxifen.
Monitoring and Follow-Up: Patients should be aware of the importance of regular monitoring and follow-up appointments with their healthcare provider to assess the effectiveness of Tamoxifen therapy and monitor for any potential side effects or complications.

Monitoring and Follow-up: Tamoxifen 20 Mg

Regular monitoring is crucial during Tamoxifen 20 mg therapy to assess treatment efficacy, manage potential side effects, and ensure patient safety. This involves monitoring certain parameters and scheduling follow-up appointments at specific intervals.

Monitoring Parameters

Monitoring parameters are essential for tracking the effectiveness of Tamoxifen 20 mg therapy and detecting any potential adverse effects. The most common parameters include:

Liver function tests (LFTs): Tamoxifen 20 mg can affect liver function. Regular LFTs are crucial to monitor liver enzymes, such as AST and ALT, to detect any signs of liver damage.
Complete blood count (CBC): Tamoxifen 20 mg can impact blood cell production. CBC helps monitor red blood cell count, white blood cell count, and platelet count to detect any potential anemia, infection, or bleeding risks.
Blood glucose levels: Tamoxifen 20 mg can affect blood sugar levels, especially in individuals with pre-existing diabetes. Regular blood glucose monitoring is essential to manage blood sugar levels effectively.
Blood pressure: Tamoxifen 20 mg can cause blood pressure fluctuations. Regular blood pressure monitoring is necessary to detect any significant changes and adjust medication if needed.
Hormone levels: Tamoxifen 20 mg is an anti-estrogen medication. Monitoring hormone levels, such as estrogen and progesterone, can help assess treatment efficacy and identify any hormonal imbalances.

Frequency and Duration of Follow-up Appointments

Follow-up appointments are scheduled to monitor treatment progress, manage side effects, and ensure patient safety. The frequency and duration of these appointments vary depending on the individual patient’s condition, response to therapy, and any potential complications.

Initial follow-up: Usually scheduled within 1-2 weeks after starting Tamoxifen 20 mg therapy to assess initial response and monitor for any adverse effects.
Subsequent follow-up: Typically scheduled every 3-6 months for routine monitoring of LFTs, CBC, and other relevant parameters.
Duration: The duration of follow-up appointments depends on the individual patient’s condition and treatment goals. For example, patients with breast cancer may require ongoing follow-up for several years after completing Tamoxifen 20 mg therapy.

Importance of Regular Assessments

Regular assessments are crucial for:

Monitoring treatment efficacy: Regular monitoring helps assess the effectiveness of Tamoxifen 20 mg therapy in achieving the desired therapeutic outcomes. This includes evaluating tumor response, disease progression, and overall patient well-being.
Managing side effects: Regular assessments help identify and manage potential side effects associated with Tamoxifen 20 mg therapy. This involves addressing symptoms, adjusting medication dosage, or implementing supportive care measures.
Ensuring patient safety: Regular monitoring helps detect any potential complications or adverse reactions to Tamoxifen 20 mg therapy, allowing for timely intervention and management to ensure patient safety.

Research and Development

Tamoxifen 20 mg, a selective estrogen receptor modulator (SERM), has been a mainstay in the treatment of breast cancer for decades. However, ongoing research continues to uncover new insights into its efficacy, safety, and potential applications beyond breast cancer. This section delves into recent research findings, ongoing clinical trials, and future directions of research and development related to Tamoxifen 20 mg.

Recent Research Findings

Recent research has shed light on Tamoxifen 20 mg’s efficacy and safety in various settings, including:

* Improved Outcomes in Early-Stage Breast Cancer: Studies have shown that Tamoxifen 20 mg, when used as adjuvant therapy after surgery for early-stage breast cancer, can significantly reduce the risk of recurrence and improve overall survival.
* Potential Benefits in Other Cancers: Research is exploring Tamoxifen 20 mg’s potential role in treating other cancers, such as endometrial cancer, ovarian cancer, and prostate cancer.
* Neuroprotective Effects: Studies have investigated Tamoxifen 20 mg’s potential neuroprotective effects in conditions like Alzheimer’s disease and Parkinson’s disease.
* Safety and Long-Term Effects: Research has examined the long-term safety of Tamoxifen 20 mg, including potential risks of cardiovascular disease, stroke, and endometrial cancer.

Ongoing Clinical Trials

Numerous clinical trials are underway to investigate the efficacy and safety of Tamoxifen 20 mg in various settings. These trials are exploring:

* New Dosing Regimens: Trials are investigating the optimal dosage and duration of Tamoxifen 20 mg therapy for different types of breast cancer.
* Combination Therapies: Studies are exploring the effectiveness of combining Tamoxifen 20 mg with other therapies, such as chemotherapy or targeted therapies, to enhance treatment outcomes.
* Prevention of Breast Cancer: Trials are evaluating the potential of Tamoxifen 20 mg to prevent breast cancer in high-risk individuals.

Future Directions of Research and Development

Future research on Tamoxifen 20 mg is likely to focus on:

* Personalized Medicine: Researchers are investigating the use of genetic testing to identify patients who are most likely to benefit from Tamoxifen 20 mg therapy.
* Novel Drug Delivery Systems: Scientists are exploring new drug delivery systems, such as nanoparticles, to improve the efficacy and reduce the side effects of Tamoxifen 20 mg.
* New Indications: Research is ongoing to explore the potential of Tamoxifen 20 mg for treating other diseases, such as inflammatory bowel disease and autoimmune disorders.

Patient Education

This guide provides essential information about Tamoxifen 20 mg, a medication commonly used for breast cancer prevention and treatment. Understanding your medication is crucial for your health and well-being. We will cover key aspects like how it works, potential side effects, and important precautions.

What is Tamoxifen 20 mg?

Tamoxifen 20 mg is a medication that belongs to a class of drugs called selective estrogen receptor modulators (SERMs). It works by blocking the effects of estrogen in certain tissues, like breast tissue. Tamoxifen is primarily used for:

* Preventing breast cancer: In women at high risk of developing breast cancer, Tamoxifen can help reduce their chances of getting the disease.
* Treating breast cancer: It is often used to treat hormone-sensitive breast cancer in women.

How does Tamoxifen 20 mg work?

Tamoxifen works by blocking estrogen from binding to its receptors in certain tissues, particularly in breast tissue. Estrogen can promote the growth of breast cancer cells. By blocking estrogen’s action, Tamoxifen can help prevent the growth of these cells.

What are the possible side effects of Tamoxifen 20 mg?

Like all medications, Tamoxifen can cause side effects. Some common side effects include:

* Hot flashes: Feeling sudden warmth in your face, neck, and chest.
* Vaginal dryness: Feeling dry or uncomfortable in your vagina.
* Menstrual irregularities: Changes in your menstrual cycle, such as missed periods or heavy bleeding.
* Nausea: Feeling sick to your stomach.
* Weight gain: Gaining weight.

Important Precautions

Here are some important precautions to consider when taking Tamoxifen 20 mg:

* Tell your doctor about all your medical conditions: This includes any allergies, existing medical conditions, and medications you are currently taking.
* Pregnancy and breastfeeding: Tamoxifen is not recommended for pregnant or breastfeeding women.
* Blood clots: Tamoxifen can increase the risk of blood clots, especially in women who smoke or have certain medical conditions.
* Liver problems: Tamoxifen can affect your liver function. If you have liver problems, you may need to be monitored closely.
* Regular checkups: Your doctor will likely want to monitor you regularly while you are taking Tamoxifen. This may involve blood tests and physical examinations.

Resources for Additional Information

If you have any questions or concerns about Tamoxifen 20 mg, talk to your doctor or pharmacist. You can also find additional information about Tamoxifen 20 mg from these resources:

* National Cancer Institute: https://www.cancer.gov/
* American Cancer Society: https://www.cancer.org/
* Food and Drug Administration (FDA): https://www.fda.gov/

Ethical Considerations

The use of Tamoxifen 20 mg, like any potent medication, raises important ethical considerations. It is crucial to balance the potential benefits of this drug with its associated risks, ensuring patient autonomy and informed consent are upheld.

Informed Consent and Patient Autonomy

Informed consent is paramount in any medical treatment, and Tamoxifen 20 mg is no exception. Patients must be fully informed about the potential benefits, risks, and alternatives to Tamoxifen 20 mg therapy. This information should be presented in a clear and understandable manner, allowing patients to make informed decisions about their treatment.

Patients should understand the specific indications for Tamoxifen 20 mg therapy, including its effectiveness in reducing the risk of breast cancer recurrence or preventing breast cancer in high-risk individuals.
They should be aware of the potential side effects, including the possibility of serious adverse events such as blood clots, stroke, and uterine cancer.
Patients should be informed about alternative treatment options, including surgery, radiation therapy, and other medications.
Patients should be given adequate time to consider the information and ask questions before making a decision.

It is essential to respect patient autonomy, allowing them to make decisions about their own healthcare based on their values and preferences. This includes the right to refuse treatment, even if it is recommended by a healthcare professional.

Risks and Benefits in Different Patient Populations

The risks and benefits of Tamoxifen 20 mg therapy can vary depending on the patient’s age, health status, and individual circumstances. For example, in postmenopausal women with breast cancer, Tamoxifen 20 mg has been shown to be effective in reducing the risk of recurrence. However, in premenopausal women, Tamoxifen 20 mg may increase the risk of uterine cancer.

In younger women, the potential risks of Tamoxifen 20 mg therapy may outweigh the benefits, especially if they are not at high risk for breast cancer.
In older women, the risk of developing osteoporosis may be increased with Tamoxifen 20 mg therapy.
In patients with a history of blood clots or stroke, Tamoxifen 20 mg therapy may increase the risk of these events.

It is crucial to carefully weigh the potential risks and benefits of Tamoxifen 20 mg therapy in each individual patient to ensure that the treatment is appropriate.

Ethical Dilemmas

The use of Tamoxifen 20 mg can present ethical dilemmas, particularly in situations where the risks and benefits are not clear-cut. For example, in patients with a strong family history of breast cancer but no personal history, the decision to start Tamoxifen 20 mg therapy can be challenging.

The potential benefits of preventing breast cancer may be outweighed by the risks of side effects.
The decision may be further complicated by the patient’s age, health status, and personal preferences.

In such cases, it is essential to engage in open and honest communication with the patient, providing them with all the necessary information to make an informed decision.

Tamoxifen 20 mg represents a significant advancement in the realm of cancer therapy and preventive medicine. Its versatility and efficacy in treating and preventing breast cancer, along with its potential applications in other medical areas, highlight its importance in modern healthcare. However, it is essential to remember that Tamoxifen 20 mg, like any medication, carries potential side effects and interactions. Consulting with a healthcare professional is paramount to ensure safe and effective use of this powerful drug.

Tamoxifen 20 mg is a medication commonly prescribed for breast cancer treatment, but it’s important to remember that every individual responds differently to medication. While researching tamoxifen, you might come across information about other medications like mestinon , which is used to treat myasthenia gravis. Both medications have distinct mechanisms of action and applications, and it’s crucial to consult with a healthcare professional for personalized guidance and treatment plans related to tamoxifen 20 mg.