Trexall

Less Common Side Effects (1 in 100 to 1 in 10)

• Alopecia (Hair Thinning): While not as severe as with high-dose chemotherapy, some patients notice thinning of the hair.
• Photosensitivity: Increased sensitivity to sunlight, leading to easier sunburns or skin rashes.
• Dizziness and Headaches: These may occur shortly after administration.
• Leukopenia: A mild drop in white blood cell counts, which may slightly increase the risk of minor infections.

• Pneumonitis: An inflammation of the lungs that can cause a dry cough and shortness of breath. This is a medical emergency.
• Stevens-Johnson Syndrome (SJS): A severe, life-threatening skin reaction characterized by peeling skin and blisters.
• Encephalopathy: Primarily seen with high-dose intravenous or intrathecal use, leading to confusion or seizures.

> Warning: Stop taking Methotrexate and call your doctor immediately if you experience any of these symptoms.

• Signs of Infection: Fever, persistent sore throat, or chills. Methotrexate suppresses the immune system, making it harder to fight off even minor illnesses.
• Unusual Bleeding or Bruising: This may indicate thrombocytopenia (low platelet count), which increases the risk of internal bleeding.
• Severe Abdominal Pain: Could indicate GI perforation or severe hepatotoxicity.
• Yellowing of the Eyes/Skin (Jaundice): A primary sign of liver damage or failure.
• Shortness of Breath or Dry Cough: These can be early warning signs of Methotrexate-induced lung disease, which can be fatal if not treated.
• Dark Urine or Decreased Urination: Signs of potential kidney damage.

With prolonged use (years), Methotrexate carries specific risks that require ongoing monitoring:

• Liver Fibrosis and Cirrhosis: Chronic low-dose therapy can lead to scarring of the liver. This risk is higher in patients with obesity, diabetes, or a history of alcohol use.
• Secondary Malignancies: There is a slightly increased risk of developing certain lymphomas, although this is sometimes reversible upon stopping the drug.
• Bone Marrow Suppression: Chronic suppression of red cells, white cells, and platelets can occur, requiring periodic 'drug holidays.'

The FDA has issued several Black Box Warnings for Methotrexate due to its potential for severe toxicity:

1. 1Fetal Death and Teratogenicity: Methotrexate can cause severe birth defects or fetal death. It is strictly contraindicated in pregnancy.
2. 2Impaired Drug Elimination: Patients with renal impairment are at high risk for toxicity.

• Hepatotoxicity: Chronic use can lead to liver failure.
• Pulmonary Toxicity: Methotrexate-induced lung disease can occur at any time during therapy.
• GI Toxicity: Can lead to hemorrhagic enteritis and intestinal perforation.
• Bone Marrow Suppression: Can cause sudden, severe drops in blood cell counts.
• Secondary Infections: Increased susceptibility to opportunistic infections like Pneumocystis jirovecii.

Report any unusual symptoms to your healthcare provider immediately. Regular blood work (usually every 8-12 weeks once stable) is the best way to catch these side effects early.

• Allergic Reactions: Anaphylaxis and severe skin reactions (SJS/TEN) have been reported. If you develop a widespread rash or hives, stop the drug and seek emergency care.
• Infection Risk: Methotrexate is an immunosuppressant. You may be more susceptible to infections, and common infections may become more severe. Avoid contact with people who have contagious illnesses like the flu or chickenpox.
• Vaccinations: Live vaccines (such as the MMR or yellow fever vaccine) should generally be avoided while taking Methotrexate, as the suppressed immune system may allow the vaccine virus to replicate uncontrollably.
• Sun Exposure: Methotrexate can make your skin more sensitive to UV light. Use high-SPF sunscreen and wear protective clothing to avoid severe 'recall' sunburns.

To ensure safety, your healthcare provider will require regular laboratory monitoring. This typically includes:

• Complete Blood Count (CBC): To check for anemia (low red cells), leukopenia (low white cells), and thrombocytopenia (low platelets).
• Liver Function Tests (LFTs): To monitor for elevations in enzymes (ALT/AST) and bilirubin that indicate liver stress.
• Serum Creatinine: To assess kidney function and ensure the drug is being cleared from the body effectively.
• Chest X-ray: May be performed before starting therapy and if you develop respiratory symptoms to check for lung inflammation.

Methotrexate can cause dizziness, fatigue, and blurred vision, particularly in the 24 hours following your dose. Do not drive or operate heavy machinery until you know how the medication affects you.

Strict Avoidance Recommended: Alcohol significantly increases the risk of Methotrexate-induced hepatotoxicity (liver damage). Most clinical guidelines recommend that patients on Methotrexate abstain from alcohol entirely or limit intake to no more than one standard drink per week, and only if liver tests remain perfect.

Do not stop taking Methotrexate suddenly without consulting your doctor, as this can cause a 'flare' of your autoimmune symptoms. While there is no 'withdrawal syndrome' in the traditional sense, the underlying disease can worsen rapidly. If the drug must be stopped due to toxicity, your doctor will manage the transition to a different therapy.

> Important: Discuss all your medical conditions, especially lung, liver, or kidney disease, with your healthcare provider before starting Methotrexate.

• Penicillins: May reduce the renal clearance of Methotrexate.
• Theophylline: Methotrexate may decrease the clearance of theophylline, used for asthma, requiring dose adjustments of the latter.
• Retinoids (e.g., Acitretin): Increased risk of hepatotoxicity when used together for psoriasis.

• Caffeine: Some studies suggest that high caffeine intake may reduce the efficacy of Methotrexate in RA patients by interfering with the adenosine receptor pathway. If your symptoms are not well-controlled, your doctor may suggest limiting coffee intake.
• Dairy: High doses of dairy products at the time of oral administration might slightly decrease absorption, though this is rarely clinically relevant for weekly dosing.
• Folate-Rich Foods: While a healthy diet is encouraged, consuming massive amounts of folic acid-fortified foods simultaneously with your dose might theoretically reduce efficacy, though this is why daily supplementation is carefully timed.

• Echinacea: May interfere with the immunosuppressive effects of Methotrexate.
• St. John's Wort: Can affect liver enzymes and potentially alter the metabolism of various drugs, although its specific effect on Methotrexate is less clear than with other medications.
• Vitamin B9 (Folic Acid): While prescribed to reduce side effects, taking too much can potentially reduce the efficacy of the drug's anti-cancer properties. Always follow the specific dose prescribed by your doctor.

Methotrexate can interfere with certain laboratory tests:

• Skin Tests: It may suppress the response to tuberculin skin tests (PPD), leading to false-negative results.
• Blood Tests: It can cause elevations in uric acid levels, which may complicate the diagnosis of gout.

For each major interaction, the primary mechanism is usually renal competition (the drugs fight for the same exit door in the kidneys) or pharmacodynamic synergy (both drugs attack the same pathway, like folate metabolism). The consequence is almost always an increased risk of toxicity (low blood counts, mouth sores, liver damage). Management typically involves frequent blood monitoring or switching to a non-interacting alternative.

> Important: Tell your doctor about ALL medications, supplements, and herbal products you are taking, including over-the-counter pain relievers.

These conditions require a careful risk-benefit analysis and intensive monitoring:

• Renal Impairment: Since the kidneys are the primary exit route, any decrease in function causes the drug to 'back up' in the system, leading to systemic toxicity.
• Active Infections: Treatment should usually be paused if a patient develops a significant infection (like pneumonia or a severe UTI) until the infection is cleared.
• Pulmonary Disease: Patients with pre-existing lung fibrosis or severe COPD may be at higher risk for Methotrexate-induced pneumonitis.
• Peptic Ulcer Disease: Methotrexate can cause GI irritation and may lead to perforation in patients with active ulcers.

While Methotrexate is a unique molecule, patients who have had severe hypersensitivity reactions to other folate antagonists (like Pemetrexed or Pralatrexate) should be approached with extreme caution, as cross-reactivity is possible. There is no known cross-sensitivity with common antibiotics like Penicillin or Sulfa drugs, though they may interact pharmacologically.

> Important: Your healthcare provider will evaluate your complete medical history, including a baseline chest X-ray and extensive blood work, before prescribing Methotrexate.

Methotrexate is a standard treatment for polyarticular juvenile idiopathic arthritis (pJIA) in children aged 2 and older.

• Considerations: Children generally tolerate Methotrexate better than adults but require frequent monitoring of liver function and blood counts. There are concerns regarding the long-term impact on growth and fertility, though current data suggest that low-dose weekly therapy does not significantly impair normal development when monitored correctly.
• Oncology: It is a mainstay for pediatric ALL, where it is used in much higher doses under strict inpatient supervision.

Elderly patients (65+) are at a significantly higher risk for Methotrexate toxicity.

• Renal Function: Aging naturally reduces the glomerular filtration rate (GFR). Even if a 'normal' serum creatinine is seen, the actual clearance may be low.
• Polypharmacy: Seniors are more likely to be on interacting medications like PPIs or NSAIDs.
• Toxicity: Fatalities from bone marrow suppression are more common in the elderly. Doctors often start with very low doses (e.g., 5 mg to 7.5 mg weekly) for this population.

As Methotrexate is 80-90% renally excreted, kidney health is the most important factor in preventing toxicity.

• Dosing: For GFR < 60 mL/min, significant dose reductions are required. If GFR is < 30 mL/min, the drug is typically avoided entirely.
• Dialysis: Methotrexate is not effectively removed by standard hemodialysis. High-flux dialysis or glucarpidase may be needed in toxicity cases.

Patients with pre-existing hepatic impairment should not use Methotrexate. The drug can cause direct hepatotoxicity, leading to fibrosis and cirrhosis. In patients with obesity or diabetes (who may have non-alcoholic fatty liver disease), the risk of liver damage is increased, and more frequent LFT monitoring is required.

> Important: Special populations require individualized medical assessment and often more frequent laboratory monitoring than the general population.

Pharmacokinetics

| Parameter | Value |

|---|---|

| Bioavailability | 60% - 90% (Low dose); <60% (High dose) |

| Protein Binding | ~50% (Mainly Albumin) |

| Half-life | 3 - 10 hours (Low dose); 8 - 15 hours (High dose) |

| Tmax | 1 - 2 hours (Oral); 30 - 60 mins (IM) |

| Metabolism | Hepatic & Intracellular (Polyglutamation) |

| Excretion | Renal 80-90%, Fecal <10% |

• Molecular Formula: C20H22N8O5
• Molecular Weight: 454.44 g/mol
• Solubility: Practically insoluble in water, alcohol, and chloroform; soluble in dilute solutions of alkali hydroxides.
• Structure: It consists of a pteridine ring linked to p-aminobenzoic acid and L-glutamic acid. It is chemically very similar to folic acid, differing only by the substitution of an amino group for a hydroxyl group on the pteridine ring and a methyl group on the amino nitrogen.

Methotrexate is the prototypical folate analog metabolic inhibitor. Within rheumatology, it is the 'anchor' DMARD. Related medications in the antifolate class include Pemetrexed (Alimta) and Pralatrexate (Folotyn), though these are used exclusively in oncology and have different safety profiles.