Methotrexate
Also known as: Amethopterin
Methotrexate is an analogue of folic acid and is a widely used antimetabolite anticancer drug, with a role in the treatment of both haematological malignancies perticularly leukaemias and solid tumours.Methotrexate is also used commonly as an immunosupressive agent in the treatment of a number of autoimmune and inflammartory disorders.
Primary Characteristics
Methotrexate is also known as Amethopterin.
It is of Synthetic origin and belongs to Benzoyl Glutamic Acid.
It belongs to Dihydrofolate reductase inhibitor pharmacological group on the basis of mechanism of action and also classified in Antineoplastic Agnet, Antimetabolite pharmacological group.
Molecular Weight: 454.5 · pKa: 4.8, 5.5 · Solubility in Water: practically insoluble · Solubility in Alcohol: practically insoluble · Non-proprietary name: Methotrexate.
Pharmacokinetics
Distribution: Methotrexate has a volume of distribution is 0.4-0.8 l/kg. plasma protein binding is 60%.
Elimination: it is metabolised via Hepatic, plasma half-life is 8-10 hr, renal excretion is 81(72-90)%.
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Indications
Methotrexate is primarily indicated in conditions like Adjunct in epilepsy, Bone marrow transplantation, Breast cancer, Choriocarcinoma, Endometriosis, Gastric cancer, Graft rejection, Graft versus host disease, Granulomatous disease, Head and neck cancer, Juvenile rheumatoid arthritis, Leukaemia, Lymphocytic leukaemia, Lymphoma, Medulloblastoma, Mycoses, Non-hodgkin's lymphoma, Osteosarcoma, Ovarian cancer, Pityriasis, Premedication, Psoriasis, Rheumatoid arthritis, Status epilepticus; seizures in neurosurgery, Wegeners granulomatosis.
Methotrexate is also indicated for secondary conditions like Crohn's disease, Dermatomyositis, Hydatidiform mole, Systemic lupus erythematosus.
Contraindications
Methotrexate is contraindicated in conditions like Neutropenia, Ulcerative colitis, Thrombocytopenia, Renal failure, Bone marrow depression, Pulmonary disease.
Dosage
Methotrexate's dosage details are as follows:
| Dose | Single Dose | Frequency | Route | Instructions |
|---|---|---|---|---|
| Adult Dosage | ||||
| 1.562 mg/kg | 1.562 mg/kg | — | Lymphosarconas. | |
| 7.5 mg | 7.5 mg | — | For Rheumatoid artheitis once weekly. | |
| 12 mg/sq.meter | 12 mg/sq.meter | — | Intra Thecal | Once a week |
| 2.5 mg/kg | 2.5 mg/kg | Every 24h | IV | In leukemia every 14 days. |
| 17.5 mg/m2 | 17.5 mg/m2 | — | PO | Breast cancer |
| 17.5 mg | 17.5 mg | — | PO | Psoriasis (once a week) |
| 22.5 mg | 22.5 mg | Every 24h | PO,IM | For 5 days in prophylaxis of choriocarcinoma. |
| Paediatric Dosage (20kg) | ||||
| 10 mg/sq.meter | 10 mg/sq.meter | — | Intra Muscular | Per Week for Rheum. Arthritis |
| 200 mg/sq.meter | 200 mg/sq.meter | — | Intra Venous | For Induction |
| 1200 mg/sq.meter | 1200 mg/sq.meter | — | IV Infusion | Maintenance, Over 24 Hours |
| 10 mg/sq.meter | 10 mg/sq.meter | — | Oral | Per Week for Rheum. Arthritis |
| Neonatal Dosage (3kg) | ||||
| No data. | ||||
Drug Interactions
Always consult your physician for the change of dose regimen or an alternative drug of choice that may strictly be required.
Side Effects
Methotrexate in overdosage may give rise to further complications which include Hepatotoxicity , Coma , Seizures , Neurotoxicity , Hepatotoxicity , Eelvated hepatic enzymes , Chemical arachnoiditis , Motor paralysis of extremities , Cranial nerve palsy , Dementia , Dementia, Nuchal rigidity.
Methotrexate produces potentially life-threatening effects which include Myelosuppression , Nephrotoxicity, GI mucositis. Careful monitoring is needed with proper medical management.
The signs and symptoms that are produced after acute overdosage of Methotrexate are Myelosuppression , Motor paralysis of extremities.
Methotrexate is known to cause more or less tolerable side effects which are usually transient. These include Cough , Desquamation , Erythema, Fever, Intestitial pulmonary infitterate, Nausea, Ocular irritation, Pleuritis , Pneumonitis, Vasculitis, Vomiting .
Warnings / Precautions
Interference in Pathology
Methotrexate may interfere in the diagnosis of False +ve result of protein in CSF .
Available Brands
Storage Conditions
Drug Classification
- 1.2.4 — Disease modifying antirheumatic drugs
- 2.8.2 — Cytotoxic (anti-neoplastic) drugs