Indications

February 14, 2019 Critical Thinking

Indications: Methotrexate (Rasuvo®) is a weekly subcutaneous injection into the abdomen or thigh for managing severe active rheumatoid arthritis (RA) in adults and polyarticular juvenile idiopathic arthritis (pJIA) in adolescents, which is inflammation in multiple joints of the fingers and hands without a known cause. Rasuvo® may also be used as a second line treatment for controlling psoriasis in adults that have had no success with other treatments.
Boxed Warning: Severe toxic reactions, embryo-fetal toxicity, and death – Methotrexate may cause very serious toxic reactions of the kidney, liver, skin, and bone marrow or possibly death. Potentially fatal opportunistic infections or malignant lymphomas may also occur. Birth defects and/or fetal death are also possible with the administration of methotrexate by a pregnant woman.
Contraindications:
1. Pregnancy – Methotrexate may cause embryonic abnormalities or fetal death if taken by a woman during pregnancy.
2. Nursing mothers – Breast-fed infants may experience serious adverse effects caused by methotrexate if the nursing mother is receiving Rasuvo®.
3. Alcoholism or liver disease – Patients with alcoholism or alcoholic liver disease including a fatty liver, liver fibrosis, or liver cirrhosis may experience an increased risk of hepatic toxicity.
4. Immunodeficiency syndromes – Patients who are immunodeficient may risk a potentially fatal opportunistic infection.
5. Preexisting blood dyscrasias – Patients with bone marrow deficiencies as Rasuvo® may suppress the production of blood cells and platelets.
Warnings and Precautions:
1. Organ system toxicity – Rasuvo® potentially may cause toxic reactions including gastrointestinal toxicity, hematologic toxicity, hepatic toxicity, neurologic toxicity, pulmonary toxicity, renal toxicity, and skin toxicity. Deaths have been reported due to various adverse effects so patients should be closely monitored for toxicity.
2. Embryo-Fetal Toxicity – Methotrexate has reportedly caused birth defects and/or fetal death so Rasuvo® is not recommended for women planning to become pregnant or are pregnant unless there is evidence that the expected benefits for the women outweigh the potential risks to the fetus. A couple also should not plan to become pregnant if either partner is receiving Rasuvo®.
3. Effects on Reproduction – Methotrexate may cause infertility, low sperm count, and abnormal menstrual cycles.
4. Patients with Impaired Renal Function – The risk of toxicity is increased in patients with impaired renal function as methotrexate elimination may be reduced.
5. Malignant Lymphomas & Tumor Lysis Syndrome – Non-Hodgkin’s lymphoma and other tumors have been seen in some patients who take Rasuvo®. Methotrexate may also cause lysis of fast growing tumors already present in patients.

Drug Interactions:
1. Aspirin ; Non-Steroidal Anti-Inflammatory Drugs – NSAIDs can increase the blood levels of methotrexate which may lead to hematologic and gastrointestinal toxicity or even death. High doses of methotrexate and NSAIDs should not be administered concurrently. NSAIDs should be used with caution with low doses of methotrexate as animal studies showed that NSAIDs may reduce the tubular secretion of methotrexate which may cause toxicity.
2. Proton Pump Inhibitors (PPIs) ; H2 Blockers – Proton pump inhibitors (PPIs) like omeprazole, esomeprazole, and pantoprazole may increase blood levels of methotrexate which can lead to toxicity. Therefore caution should be used when high doses of methotrexate is administered with PPIs.
3. Oral Antibiotics – Some oral antibiotics like tetracycline and chloramphenicol may reduce intestinal absorption of methotrexate. Penicillins may decrease renal excretion of methotrexate leading to increased levels in the blood which can cause hematologic and gastrointestinal toxicity. Caution should be used when using oral antibiotics with methotrexate since toxicity is possible.
Use in Specific Populations:
1. Pregnancy – Pregnancy category X -; Methotrexate should not be given to a pregnant woman as it may be toxic to a fetus. Methotrexate has been known to cause birth defects or fetal death.
2. Nursing Mothers – Methotrexate has been found in human breast milk at a 0.08:1 ratio to plasma concentration. This shows that methotrexate has the potential to cause adverse effects to a breast-fed infant from a nursing mother receiving Rasuvo®.
3. Pediatric Use – Since Rasuvo® is not indicated for psoriasis in pediatric patients, the safety and effectiveness of methotrexate for this purpose has not been evaluated. Studies determining the safety of Rasuvo® for the intended purpose of managing pJIA in patients 2 to 16 years old showed incidence of nausea/vomiting and a smaller incidence of stomatitis, diarrhea, leukopenia (low white blood cell count), and dizziness.
4. Geriatric Use – The difference in safety and response to Rasuvo® between elderly and younger patients could not be determined as clinical studies did not include enough patients over 65 years old. Elderly patients should be monitored for toxic reactions as it is more common that they have decreased kidney function, decreased folate levels, or are concurrently taking multiple drug therapies.
Nonclinical Toxicology:
1. Carcinogenesis, Mutagenesis, Impairment of Fertility – There is no human data evaluating the risk of cancer with administration of methotrexate while the animal studies evaluating the cancer potential were shown to be inconclusive. Genotoxicity was found as there was chromosomal damage to human bone marrow cells and animal somatic cells but it is unknown if these findings are clinically significant. Low doses of methotrexate may cause tumors and Non-Hodgkin’s lymphoma which can regress after withdrawal of the drug. Methotrexate causes birth defects and fetal death in humans along with infertility, low sperm count, and abnormal menstrual cycles.