Niraparib

Mechanism of action

✂Poly(ADP-ribose) polymerases PARP1 and PARP2Niraparib

ⓘ The figure shows niraparib in the NAD+ site of the human PARP1 catalytic domain.

Niraparib inhibits PARP1 and PARP2 and traps them on DNA, so single-strand breaks become lethal double-strand breaks in tumours with BRCA mutations or other homologous recombination defects. It also inhibits the dopamine, noradrenaline and serotonin transporters, which explains its effects on blood pressure and heart rate.

1. Inhibits PARP1/2 and traps them on DNA
2. Homologous recombination-deficient tumour cells die
3. Off-target block of monoamine transporters raises BP

Indications

• Maintenance in advanced ovarian, fallopian tube or primary peritoneal cancer after a response to first-line platinum chemotherapy. Ovarian cancer →
• Maintenance in recurrent disease with germline BRCA mutation after a response to platinum. Ovarian cancer →

Adverse effects

Common

• Nausea, vomiting, constipation, heartburn
• Thrombocytopenia and anaemia
• Fatigue, headache, dizziness
• Trouble sleeping and anxiety
• Dry mouth, mouth sores, taste changes

Contraindications

• No absolute contraindications in the label apart from hypersensitivity; see the warnings

Key interactions

Other bone-marrow-suppressing drugs

Additive anaemia, neutropenia and thrombocytopenia.

CYP3A4 inhibitors and inducers

Less relevant than for other PARP inhibitors, because niraparib is cleared mainly by carboxylesterases.

What is monitored

• Complete blood count, especially platelets
• Blood pressure and heart rate regularly
• Neurological symptoms (headache, confusion, vision)

Administration and safety

• Oral; swallowed whole, never split, crushed, chewed or opened.
• Can be taken at bedtime to reduce nausea.
• If the patient vomits after a dose, the dose is not repeated; the next one is taken at the usual time.

Pregnancy and breastfeeding

Avoid in pregnancy. Can harm the fetus: a pregnancy test is done before starting, effective contraception is used during treatment and for a time afterwards (by women and by men with partners who could conceive), and breastfeeding is avoided.

Nursing care

• Review blood counts before and during treatment; teach to report pallor, fatigue, bruising, bleeding or fever.
• Measure blood pressure and pulse at each visit and teach home checks if ordered.
• Teach to report severe headache, confusion or vision changes at once.
• Confirm a negative pregnancy test before the first dose and teach contraception during treatment and afterwards.

Pharmacokinetics

Absorption

Oral capsules, once daily, with or without food; at bedtime if it causes nausea.

Metabolism

Inactivated mainly by carboxylesterases, not mainly by CYP enzymes.

Half-life

About 36 hours.

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Connections

← Back to the class: PARP inhibitors

Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.

Sources: Niraparib: MedlinePlus Drug Information (MedlinePlus (U.S. National Library of Medicine), 2020); Niraparib Tosylate Monohydrate - NCI (National Cancer Institute, 2023); ATCDDD - ATC/DDD Index (WHO Collaborating Centre for Drug Statistics Methodology, 2026).

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Representative model, for educational purposes only.