Carbamazepine

What it is

Carbamazepine is an anticonvulsant that blocks voltage-gated sodium channels and slows the repeated firing of overactive nerves. It is prescription-only and is used for epilepsy and for nerve pain such as trigeminal neuralgia and other neuropathies. It works on the underlying excitability rather than acting as an ordinary painkiller.

A usual adult range, not a national label — the dose and the timing differ by country and by product.

Used for

• Epilepsy
• Neuropathy

Approved uses differ by country — some of these may be off-label or unapproved where you live.

What to know while taking it

It is taken with food. Grapefruit blocks the enzyme that clears it and raises its level, while carbamazepine itself is a strong enzyme inducer that weakens the anticoagulant warfarin and can make combined ethinylestradiol and progestin contraception unreliable. Sodium, white blood cells and ALT are monitored because the drug can lower sodium, suppress the marrow and affect the liver, and it depletes vitamin D, folate and biotin, so vitamin D is often checked as well. It is not stopped abruptly.

When to see a doctor

Any rash means stopping and calling a doctor at once, particularly with fever, sore throat, mouth ulcers or blistering. Confusion, headache with nausea, unsteadiness, easy bruising or repeated infections also mean seeing a doctor rather than waiting.

Worth knowing

• Avoid grapefruit
• Can lower sodium
• Any rash means stop and call a doctor
• Do not stop abruptly

Markers to watch

• Sodium
• White blood cells
• ALT
• Vitamin D (25-OH)

Nutrients affected

• vitaminD — depleted by (Calcium, ionized, Calcium, total, Testosterone)
• vitaminB9 — depleted by (Folate, Hemoglobin, Homocysteine)
• vitaminB7 — depleted by