WHAT IS THIS MEDICINE AND WHAT IS IT USED FOR?
Pemetrex contains pemetrexed, a chemotherapy medicine that works by
blocking several enzymes involved in folate metabolism — processes that cancer
cells need to make DNA and divide. By disrupting these processes
simultaneously, pemetrexed stops cancer cells from growing and multiplying.
The 100mg vial is used for patients with lower body surface area or for
dose-adjusted protocols.
It is used in adults for: non-small cell lung cancer (NSCLC) — both
non-squamous NSCLC (in combination with platinum-based chemotherapy as
first-line treatment or as maintenance therapy) and in combination with
pembrolizumab for first-line treatment of metastatic NSCLC; and malignant
pleural mesothelioma (a type of cancer affecting the lining of the lungs, often
linked to asbestos exposure) — in combination with cisplatin.
3. HOW TO TAKE THIS MEDICINE
Administered as a 10-minute intravenous infusion in hospital. The
standard dose is 500mg/m² on day 1 of each 21-day cycle. The 500mg vial is used
for patients whose calculated dose falls within or close to this amount based
on their body surface area.
Your oncologist and hospital pharmacist will calculate the exact dose and
prepare the infusion. As with the 100mg vial: mandatory folic acid (daily oral)
and vitamin B12 (intramuscular injection every 9 weeks) supplementation must be
in place before the first infusion.
The mandatory vitamin supplementation protocol — daily folic acid
starting at least 5 to 7 days before the first infusion and vitamin B12
injection before the first infusion — applies identically to the 500mg vial. Do
not proceed with pemetrexed treatment without confirming vitamins have been
started. Dexamethasone (steroid) prophylaxis is also given to prevent skin
rash.
⚠ PATIENT TIP: The 100mg and 500mg vials contain
the same medicine — only the vial size differs. The same importance applies to
your vitamin supplements, NSAID avoidance, blood count monitoring, and fever
emergency plan as described in entry 144.
4. POSSIBLE SIDE EFFECTS
|
How Common? |
Side Effects |
|
Very common |
Neutropenia, anaemia,
thrombocytopenia, nausea, vomiting, mouth sores, fatigue, rash, diarrhoea,
hair thinning, peripheral neuropathy |
|
Common |
Febrile neutropenia
(fever >38°C with low counts — medical emergency). Severe mouth ulcers.
Severe skin reactions (very rare). Acute kidney injury. |
5. WHO SHOULD NOT TAKE THIS MEDICINE
Must not be given without vitamin supplementation in place. Kidney
function must be assessed before each cycle. Not safe in pregnancy.
⚠ VITAMIN SUPPLEMENTATION IS MANDATORY FOR BOTH
VIAL SIZES: The mandatory folic acid and vitamin B12 protocol applies equally
regardless of vial size. Never administer pemetrexed without confirming vitamin
supplementation is in place.
⚠ NSAID AVOIDANCE: Avoid ibuprofen, naproxen,
diclofenac, and other NSAIDs for at least 2 days before and 2 days after each
infusion (5 days for long-acting NSAIDs). Use paracetamol instead.
6. MEDICINES THAT INTERACT WITH THIS TREATMENT
Avoid NSAIDs around each infusion. Avoid nephrotoxic drugs. Cisplatin and
carboplatin are commonly co-administered per protocol.
7. HOW TO STORE THIS MEDICINE
Store below 25°C. Reconstituted and diluted infusion solutions should be
used within the timeframe specified by the hospital pharmacy. Single-use vial —
discard unused portion.
8. PRESCRIPTION REQUIREMENT
|
Field |
Details |
|
Status |
Prescription Only
Medicine (POM) — Specialist (oncology) prescription required; hospital
pharmacy preparation and administration only |
9. GUIDANCE FOR PATIENTS & CAREGIVERS
This is the same medicine as the 100mg vial — just a larger vial size.
All the same guidance applies: take your daily folic acid tablets, receive your
vitamin B12 injection as scheduled, avoid ibuprofen around your infusion dates,
attend blood test appointments, and go to hospital immediately if your
temperature reaches 38°C or above. See entry 144 for full guidance.
10. PHARMACIST & PRESCRIBER NOTES
|
Field |
Details |
|
Clinical Dispensing
Notes |
500mg vial is the
standard size for most adult patients based on BSA calculation. All vitamin
supplementation requirements (folic acid daily + vitamin B12 IM every 9
weeks), dexamethasone prophylaxis, renal function monitoring (eGFR before
each cycle — dose reduce or omit if eGFR <45), NSAID interaction
counselling, FBC monitoring, and febrile neutropenia emergency protocols are
identical to the 100mg vial (entry 144). Verify BSA and dose calculation
before preparation. Embryo-fetal toxicity: contraception required during and
6 months (male patients) or during + 6 months post-treatment (female
patients). |
11. FREQUENTLY ASKED QUESTIONS
Q: How does the hospital calculate my dose?
Your oncologist and pharmacist calculate your dose based on your body
surface area (BSA), which is worked out from your height and weight. The target
dose is usually 500mg per square metre of BSA. This calculation is done before
each cycle to account for any changes in weight.
Q: Why might I receive multiple vials in a treatment session?
If your calculated dose exceeds 500mg (which occurs in taller or heavier
patients), more than one 500mg vial may be needed to make up the full dose. The
hospital pharmacy will prepare the exact required volume.
Q: How do I know the vitamins are working?
If you are taking folic acid consistently and receiving your B12
injections on schedule, your blood counts and tolerance of treatment are
typically better than if you were not taking them. Your care team will monitor
your blood counts to confirm the treatment is being tolerated safely.