Skip to main content

Reditrex Injection Dosage

Generic name: METHOTREXATE 7.5mg in 0.3mL
Dosage form: injection, solution

Medically reviewed by Last updated on Dec 29, 2021.

Important Dosing Information

RediTrex is a single-dose prefilled syringe (in a needle safety device) for once-weekly subcutaneous use only [see Warnings and Precautions ( 5.5)] . Administer RediTrex in the abdomen or the thigh. RediTrex is available in the following dosage strengths: 7.5, 10, 12.5, 15, 17.5, 20, 22.5 and 25 mg. Use another formulation of methotrexate for alternative dosing in patients who require oral, intramuscular, intravenous, intra-arterial, intrathecal dosing, doses less than 7.5 mg per week, doses more than 25 mg per week, high-dose regimens, or dose adjustments of less than 2.5 mg increments.

Rheumatoid Arthritis including Polyarticular Juvenile Idiopathic Arthritis

Recommended starting dose of methotrexate:

Adult RA: 7.5 mg once weekly.

pJIA: 10 mg/m 2 once weekly.

For patients switching from oral methotrexate to RediTrex, consider any differences in bioavailability between oral and subcutaneously administered methotrexate [see Clinical Pharmacology ( 12.3)] .

Dosages may be adjusted gradually to achieve an optimal response. Limited experience shows a significant increase in the incidence and severity of serious toxic reactions, especially bone marrow suppression, at doses greater than 20 mg/wk in adults. Although there is experience with doses up to 30 mg/m 2/wk in children, there are too few published data to assess how doses over 20 mg/m 2/wk might affect the risk of serious toxicity in children. Experience does suggest, however, that children receiving 20 to 30 mg/m 2/wk (0.65 to 1.0 mg/kg/wk) may have better absorption and fewer gastrointestinal side effects if methotrexate is administered either intramuscularly or subcutaneously.

Therapeutic response usually begins within 3 to 6 weeks and the patient may continue to improve for another 12 weeks or more.

The optimal duration of therapy is unknown. Limited data available from long-term studies in adults indicate that the initial clinical improvement is maintained for at least two years with continued therapy. When methotrexate is discontinued, the arthritis usually worsens within 3 to 6 weeks.

The patient should be fully informed of the risks involved and should be under constant supervision of the physician. Assessment of hematologic, hepatic, renal, and pulmonary function should be made by history, physical examination, and laboratory tests before beginning, periodically during, and before reinstituting RediTrex therapy [see Warnings and Precautions ( 5.4)] . Females of childbearing potential should not be started on RediTrex until pregnancy is excluded [see Contraindications ( 4) and Warnings and Precautions ( 5.2)].

All schedules should be continually tailored to the individual patient. An initial test dose may be given prior to the regular dosing schedule to detect any extreme sensitivity to adverse effects.

Maximal myelosuppression usually occurs in seven to ten days.


Recommended starting dose of methotrexate:

Psoriasis: single weekly oral, intramuscular, subcutaneous, or intravenous doses of 10-25 mg.

For patients switching from oral methotrexate to RediTrex, consider any differences in bioavailability between oral and subcutaneously administered methotrexate [see Clinical Pharmacology ( 12.3)] .

Dosage may be gradually adjusted to achieve optimal clinical response; 30 mg/week should not ordinarily be exceeded. Once optimal clinical response has been achieved, the dosage should be reduced to the lowest possible amount of drug and to the longest possible rest period. The use of RediTrex may permit the return to conventional topical therapy, which should be encouraged.

Administration and Handling

RediTrex is a prefilled syringe intended for subcutaneous use under the guidance and supervision of a physician.

Patients may self-inject with RediTrex if a physician determines that it is appropriate, if they have received proper training in how to prepare and administer the correct dose, and if they receive medical follow-up, as necessary.

Visually inspect RediTrex for particulate matter and discoloration prior to administration.

Handle and dispose of RediTrex consistent with recommendations for handling and disposal of cytotoxic drugs 1.

Pregnancy testing

Verify the pregnancy status of females of reproductive potential prior to initiating treatment with RediTrex [ see Use in Specific Populations ( 8.1, 8.3)]

Frequently asked questions

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.