Methotrexate
Methotrexate is an antimetabolite and immunosuppressant. It works by slowing down the growth of rapidly multiplying cells, such as cancer cells and skin cells in psoriasis, and by decreasing immune system activity in rheumatoid arthritis.
Dosage by Body Weight
WARNING: Methotrexate is typically taken ONCE WEEKLY, not daily, for rheumatoid arthritis and psoriasis. Daily administration can lead to severe, potentially fatal toxicity. Dose must be highly individualized and is often accompanied by folic acid supplementation to minimize side effects.
- Body Weight
- Below 5 kg
- Dose
- Specialist calculation required
- Frequency
- Once weekly
- Tracking Notes
- Safety and efficacy are not well established in infants. Pediatric dosing is calculated strictly by Body Surface Area (BSA).
- Body Weight
- 5-7 kg
- Dose
- BSA-based dosing (typically 10-15 mg/m²)
- Frequency
- Once weekly
- Tracking Notes
- Used for Juvenile Idiopathic Arthritis. Must be managed by a pediatric rheumatologist.
- Body Weight
- 8-10 kg
- Dose
- BSA-based dosing (typically 10-15 mg/m²)
- Frequency
- Once weekly
- Tracking Notes
- Regular monitoring of kidney function, liver enzymes, and complete blood count is mandatory.
- Body Weight
- 11-15 kg
- Dose
- BSA-based dosing (typically 10-15 mg/m²)
- Frequency
- Once weekly
- Tracking Notes
- Caregivers must be fully counselled that this medication is taken only once a week, not daily.
- Body Weight
- 16-20 kg
- Dose
- BSA-based dosing (typically 10-15 mg/m²)
- Frequency
- Once weekly
- Tracking Notes
- Folic acid is often co-prescribed to be taken on non-methotrexate days to reduce mucosal and gastrointestinal toxicity.
| Body Weight | Dose | Frequency | Tracking Notes |
|---|---|---|---|
| Below 5 kg | Specialist calculation required | Once weekly | Safety and efficacy are not well established in infants. Pediatric dosing is calculated strictly by Body Surface Area (BSA). |
| 5-7 kg | BSA-based dosing (typically 10-15 mg/m²) | Once weekly | Used for Juvenile Idiopathic Arthritis. Must be managed by a pediatric rheumatologist. |
| 8-10 kg | BSA-based dosing (typically 10-15 mg/m²) | Once weekly | Regular monitoring of kidney function, liver enzymes, and complete blood count is mandatory. |
| 11-15 kg | BSA-based dosing (typically 10-15 mg/m²) | Once weekly | Caregivers must be fully counselled that this medication is taken only once a week, not daily. |
| 16-20 kg | BSA-based dosing (typically 10-15 mg/m²) | Once weekly | Folic acid is often co-prescribed to be taken on non-methotrexate days to reduce mucosal and gastrointestinal toxicity. |
Formulation
Purpose
Used to treat certain types of cancer, severe rheumatoid arthritis (including juvenile idiopathic arthritis), and severe psoriasis.
Generic Name
MethotrexateBranded Drug Names
Methotrexate is listed as a generic drug name. Common branded medicines that may contain the same active ingredient include:
Scheduled Drug
No. This medicine is generally not treated as a scheduled/prescription-only drug in common consumer references, but local rules may vary.