WHAT IS THIS MEDICINE AND WHAT IS IT USED FOR?
Palbonix contains palbociclib, a targeted cancer medicine that works by
blocking two proteins called CDK4 and CDK6 (cyclin-dependent kinases 4 and 6).
These proteins act as 'accelerators' that push cancer cells through their
growth cycle and into division. By blocking CDK4 and CDK6, palbociclib puts the
brakes on cancer cell division, slowing or stopping tumour growth.
It is used in adults for hormone receptor-positive (HR+), HER2-negative
advanced or metastatic breast cancer — the most common type of breast cancer.
It is used in combination with a hormonal medicine: either an aromatase
inhibitor (such as letrozole or anastrozole) as a first treatment for
postmenopausal women and men, or fulvestrant (following previous hormonal
therapy).
The 100mg capsule is a reduced dose — used when the standard 125mg dose
causes significant side effects, particularly a drop in white blood cell
counts.
3. HOW TO TAKE THIS MEDICINE
Palbociclib is taken as one capsule once daily for 21 days, followed by 7
days off (a 28-day cycle of 3 weeks on, 1 week off). Take the capsule with food
— a meal helps absorption and reduces nausea.
Swallow whole — do not open, crush, or chew the capsule. Take at the same
time each day. If you vomit after taking the capsule, do not take another dose
the same day — wait until the next scheduled dose.
Palbociclib is always taken alongside a hormonal medicine (an aromatase
inhibitor or fulvestrant) — confirm that both medicines are co-prescribed. The
21/7 schedule is important: the 7-day break gives bone marrow cells a chance to
recover between cycles.
⚠ PATIENT TIP: Your white blood cell count will
be checked before each cycle and at day 15 of your first two cycles. If your
counts are too low, your next cycle may be delayed or your dose reduced. This
is normal and does not mean the treatment is failing — it is a safety measure
to protect you from infection.
4. POSSIBLE SIDE EFFECTS
|
How Common? |
Side Effects |
|
Very Common |
Neutropenia (low white
blood cells — making you more vulnerable to infections), anaemia (low red
blood cells — causing tiredness), thrombocytopenia (low platelets — causing
bruising), fatigue, nausea, mouth sores, hair thinning, diarrhoea, decreased
appetite |
|
Common |
Infections
(particularly upper respiratory infections), vomiting, rash, weakness, fever |
|
Serious — Seek Urgent
Medical Help |
Fever above 38°C with
low blood counts — go to hospital immediately (febrile neutropenia, which is
a medical emergency). Unusual bruising or heavy bleeding. Signs of a serious
infection. Pulmonary embolism (blood clot in the lungs — sudden
breathlessness, chest pain). |
5. WHO SHOULD NOT TAKE THIS MEDICINE
Palbociclib should not be taken with strong CYP3A4 inhibitors or inducers
(see interactions). It should be used with caution in patients with significant
liver or kidney impairment. It is not safe during pregnancy — use effective
contraception. Tell your oncologist about all medicines, supplements, and
herbal remedies you take.
⚠ NEUTROPENIA AND INFECTION RISK: Low white
blood cell counts (neutropenia) is the most common serious side effect and
affects most patients. If you develop a fever above 38°C at any time during
treatment, go to hospital immediately — do not wait. Do not take aspirin or
ibuprofen to treat fever as this may mask your true temperature.
⚠ BLOOD COUNT MONITORING: Full blood counts are
checked before starting, before each new cycle, and at day 15 of the first two
cycles. Never skip these appointments — the results determine whether it is
safe to start your next cycle.
⚠ PREGNANCY: Palbociclib can harm an unborn
baby. Use effective contraception during treatment and for at least 3 weeks
after the last dose (women) or 3 months after (men).
6. MEDICINES THAT INTERACT WITH THIS TREATMENT
Strong CYP3A4 inhibitors (ketoconazole, voriconazole, clarithromycin,
ritonavir, grapefruit juice) increase palbociclib blood levels significantly —
avoid these combinations.
Strong CYP3A4 inducers (rifampicin, phenytoin, carbamazepine, St. John's
Wort) reduce palbociclib levels, risking treatment failure — avoid. Avoid
grapefruit and grapefruit juice. Medicines that affect the pH of the stomach
(proton pump inhibitors) may reduce palbociclib absorption slightly.
7. HOW TO STORE THIS MEDICINE
Store below 25°C. Keep in original packaging away from light and
moisture. Keep out of reach of children.
8. PRESCRIPTION REQUIREMENT
|
Field |
Details |
|
Status |
Prescription Only
Medicine (POM) — Specialist (oncology) prescription required |
9. GUIDANCE FOR PATIENTS & CAREGIVERS
Take one capsule once daily with food for 21 days, then have 7 days off,
then start the next cycle. Take it at the same time each day. Attend all blood
test appointments — these protect you by ensuring your white blood cell count
is safe before each cycle. If your temperature rises above 38°C at any time, go
to hospital immediately. Avoid grapefruit and grapefruit juice. Use effective
contraception throughout treatment. Tell all your doctors and pharmacists that
you are taking palbociclib before they prescribe anything new.
10. PHARMACIST & PRESCRIBER NOTES
|
Field |
Details |
|
Clinical Dispensing
Notes |
Confirm
co-prescription of hormonal partner medicine (aromatase inhibitor or
fulvestrant). 100mg is a reduced dose — confirm this reflects intentional
dose reduction due to tolerability (typically from 125mg). 21/7 cycle
schedule — counsel clearly. FBC monitoring: before treatment, before each
cycle, and day 15 of cycles 1 and 2. Febrile neutropenia emergency protocol
counselling (fever >38°C = immediate hospital attendance). Avoid strong
CYP3A4 inhibitors and inducers. Grapefruit avoidance. Embryo-fetal toxicity:
contraception required during treatment — women 3 weeks post-treatment, men 3
months post-treatment. Do not open or crush capsules. LFT and renal function
monitoring per oncologist schedule. |
11. FREQUENTLY ASKED QUESTIONS
Q: Will I lose my hair?
Hair thinning can occur with palbociclib but is generally less severe
than with traditional chemotherapy. Some people notice little change, while
others experience noticeable thinning. Hair typically returns to normal after
treatment ends.
Q: Is palbociclib a form of chemotherapy?
Not in the traditional sense. Palbociclib is a targeted therapy — it
specifically blocks CDK4/6 proteins that cancer cells need to divide. It is not
a cytotoxic drug (which kills all rapidly dividing cells). However, it does
affect the bone marrow's ability to produce blood cells, which is why blood
count monitoring is important.
Q: Do I need contraception?
Yes — palbociclib can harm an unborn baby. Women should use contraception
during treatment and for 3 weeks after the last dose. Men should use
contraception for 3 months after the last dose (to protect their partner).
Discuss the most appropriate contraception method with your oncologist.
Q: Why is my dose 100mg instead of 125mg?
The 125mg dose is the standard starting dose. If side effects —
particularly low blood counts — become difficult to manage, the dose is reduced
to 100mg (and then to 75mg if needed). A dose reduction does not mean the
treatment is less effective — it is a standard and expected part of managing
this medicine safely.