Abiraterone acetate, commonly known by its brand name Zytiga, treats metastatic prostate cancer. It is often co-administered with prednisone, a corticosteroid. This combination strategically manages advanced prostate cancer, aiming to improve patient outcomes and quality of life. This article explores the reasons for this combined strategy, how these medications are taken, potential side effects, and necessary precautions and monitoring.
Why Abiraterone and Prednisone are Prescribed Together
Abiraterone acetate blocks the production of androgens, male hormones that fuel prostate cancer cell growth. It targets the CYP17A1 enzyme, involved in androgen synthesis in the testes, adrenal glands, and prostate tumor tissue. By inhibiting this enzyme, abiraterone reduces testosterone and other androgen levels, slowing the progression of metastatic castration-resistant prostate cancer (mCRPC) and, in some cases, metastatic castration-sensitive prostate cancer.
Prednisone is co-administered with abiraterone as part of this treatment regimen. Abiraterone’s CYP17A1 inhibition can lead to mineralocorticoid excess. This excess can cause adverse effects, including hypertension (high blood pressure), hypokalemia (low potassium), and fluid retention.
Prednisone, a corticosteroid, is prescribed at a low dose to counteract these mineralocorticoid side effects. It acts as glucocorticoid replacement, suppressing the body’s natural cortisol production, which abiraterone can affect. This strategic pairing helps manage potential complications, ensuring the safety and tolerability of abiraterone treatment.
Specific Instructions for Taking the Medications
Correct administration of abiraterone and prednisone is paramount for therapeutic benefits and minimizing adverse effects. Abiraterone is typically prescribed at 1000 mg orally once daily, taken as two 500 mg or four 250 mg tablets. For mCRPC, abiraterone is generally combined with 5 mg prednisone twice daily. For metastatic high-risk castration-sensitive prostate cancer (mCSPC), the prednisone dose is often 5 mg once daily. A healthcare provider determines and may adjust the exact dosage and schedule for both medications based on individual patient needs.
Abiraterone must be taken on an empty stomach: no food for at least two hours before and one hour after. Food significantly increases abiraterone absorption, leading to higher drug levels and increased side effect risk. Prednisone can usually be taken with or without food; taking it with food may prevent stomach irritation. Prednisone doses are often timed with abiraterone or split for morning and evening, depending on the prescribed regimen.
Swallow abiraterone tablets whole with water; do not crush, chew, or break them. Consistent timing maintains steady drug levels. If a dose is missed, take the usual dose the following day; do not double dose. Contact a healthcare provider if more than one dose is missed.
Store both medications at room temperature, away from moisture, heat, light, and out of reach of children. Patients receiving this combination therapy should also continue with a gonadotropin-releasing hormone (GnRH) analog or have undergone bilateral orchiectomy, as these treatments lower androgen levels. Adherence to these instructions is fundamental for the safe and effective management of prostate cancer with abiraterone and prednisone.
Potential Side Effects and Management
While beneficial for prostate cancer treatment, abiraterone and prednisone can cause various side effects. Abiraterone can cause fatigue, joint pain or swelling, and hot flashes. More serious effects include liver problems, such as elevated liver enzymes, jaundice, dark urine, or upper stomach pain. Regular liver function tests are necessary, especially during initial treatment months. Severe changes may necessitate dose adjustment or temporary interruption.
Abiraterone also raises cardiovascular concerns, including hypertension (high blood pressure), hypokalemia (low potassium), and fluid retention, which prednisone helps mitigate. Despite prednisone’s protective role, patients may still experience these, along with irregular heartbeats. Abiraterone can also increase the risk of new or worsening diabetes, and contribute to bone thinning, potentially leading to increased fracture risk. Patients should promptly report symptoms like dizziness, confusion, or severe leg pain to their healthcare team.
Even at low doses, prednisone can cause side effects. Common effects include increased appetite, weight gain (particularly in the face and torso), and fluid retention. Mood changes, such as restlessness, anxiety, depression, or difficulty sleeping, are also common. Prednisone can elevate blood sugar, potentially leading to steroid-induced diabetes or worsening existing diabetes. Long-term use can also contribute to bone thinning (osteoporosis), increased infection risk due to immune suppression, and gastrointestinal irritation.
Managing these side effects requires close collaboration with the healthcare team. Regular monitoring of blood pressure, potassium levels, liver function, and blood sugar is standard. Lifestyle adjustments, such as dietary modifications and exercise, can help manage weight gain and blood sugar fluctuations. Medications like diuretics may be prescribed for fluid retention, and bisphosphonates can help protect bone health. Patients are advised to report any new or worsening symptoms to their doctor, who can then consider dose adjustments or additional supportive treatments.
Essential Precautions and Monitoring During Treatment
Before starting abiraterone and prednisone, a thorough medical history review is essential. Patients with pre-existing heart conditions (e.g., heart failure, recent myocardial infarction, or specific arrhythmias) require careful monitoring due to potential exacerbation. Liver function must be assessed; abiraterone is contraindicated in severe hepatic impairment, and dose adjustments are necessary for moderate impairment. Diabetes, uncontrolled high blood pressure, or low potassium levels need management prior to and throughout therapy, as both medications can influence these parameters.
Drug interactions are a significant area of caution. Abiraterone interacts with medications metabolized by CYP3A4, CYP2D6, and CYP2C8 enzymes. Strong CYP3A4 inducers (e.g., certain anti-seizure medications or rifampin) can decrease abiraterone levels, potentially reducing its effectiveness. Conversely, abiraterone can increase levels of drugs metabolized by CYP2D6 (e.g., thioridazine, metoprolol) or CYP2C8 (e.g., pioglitazone, repaglinide), necessitating dose adjustments for these co-administered drugs.
Prednisone interacts with a range of medications, including blood thinners like warfarin, nonsteroidal anti-inflammatory drugs (NSAIDs), and certain diabetes treatments. Patients must inform their healthcare provider about all medications, supplements, and herbal remedies (including over-the-counter products like St. John’s wort) to avoid adverse interactions.
Ongoing medical monitoring is paramount during treatment. Regular blood tests check liver function (ALT, AST, bilirubin), electrolytes (particularly potassium levels), and blood sugar. Blood pressure should be monitored monthly. Prostate-specific antigen (PSA) levels are also checked to assess treatment response. These frequent assessments allow the medical team to detect and manage potential side effects promptly, often before they become severe.
Long-term prednisone use risks adrenal insufficiency. Natural cortisol production can be suppressed, making it difficult to respond to stress. Never abruptly stop prednisone, especially during physical stress, surgery, or infection, as this can trigger an adrenal crisis. Any prednisone dosage changes should only be made under strict medical guidance, with gradual tapering if discontinuation is planned.
Abiraterone is contraindicated in pregnant women or those who may become pregnant, as it can harm a developing fetus. Men with partners of reproductive potential must use effective contraception during abiraterone therapy and for at least three weeks after the last dose. Prednisone may be used during pregnancy and breastfeeding at low doses, but close monitoring of mother and infant is advisable. Pregnant women or those who may become pregnant should avoid handling abiraterone tablets without protective gloves.