Carbamazepine (Tegretol, Equetro)

What it treats

Carbamazepine is approved by the U.S. Food and Drug Administration for acute manic and mixed episodes in bipolar I disorder (the extended-release form, sold as Equetro, carries the psychiatric label). It is also approved for certain seizure disorders and for trigeminal neuralgia.

Prescribers often reach for carbamazepine when lithium and valproate haven't worked or aren't a fit, and it can work well for mixed episodes and rapid cycling.

How it works

Carbamazepine calms overactive nerve firing by blocking sodium channels in nerve cells. Slowing those channels reduces the rapid, repetitive firing that shows up in seizures and, by extension, is thought to steady mood signaling in bipolar disorder.

The full picture of how it stabilizes mood isn't known. What is clear in practice is that it works for a subset of people who don't respond to first-line options, and that its complexity comes less from the mechanism than from how the body handles it.

Receptor mechanism (detail)

Carbamazepine blocks voltage-gated sodium channels in a use-dependent way, cutting rapid repetitive nerve firing. Its clinically striking feature is broad CYP450 induction: it speeds up its own metabolism (autoinduction) and the metabolism of many other drugs, which is why levels fall over the first 4 to 6 weeks and why interactions dominate the practical picture.

Potency and typical dosing pattern

Ranges are typical framework only, not a prescription for any individual.

Starting dose is 200 mg twice daily, titrated up to a total of 400 to 1600 mg per day divided. The target serum level is 4 to 12 micrograms/mL.

An important quirk: carbamazepine induces its own metabolism over the first 4 to 6 weeks, so a level that looks fine at week 2 may drop by week 6 even without any change in dose. Re-checking the level after autoinduction settles is standard.

Safety monitoring

• HLA-B*1502 genetic screening before starting in patients of Asian ancestry. A positive test raises the risk of Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN) sharply, and it's a reason to avoid the drug.
• CBC at baseline, then periodically, watching for a drop in white cells or platelets. Aplastic anemia and agranulocytosis are rare but boxed warnings.
• LFTs at baseline and periodically.
• Serum sodium, since carbamazepine can cause SIADH (a condition in which the body holds onto water and sodium falls).
• Serum carbamazepine level to keep within 4 to 12 micrograms/mL, with re-check after autoinduction (about 4 to 6 weeks).
• Skin surveillance in the first few months for any rash.
• A full medication review at every visit, because carbamazepine's enzyme induction changes what many other drugs are doing.

What to expect

Effects on mania build over one to two weeks at a therapeutic level. Some people find sleep improves early on because carbamazepine is somewhat sedating.

There's a specific expectation to set: a dose that felt right at week 2 may need to go up by week 6, not because the medication stopped working but because the liver has ramped up processing it faster. That's autoinduction, and it's normal.

Common side effects

Most people get some side effects. The common ones include:

• Dizziness or a mild off-balance feeling.
• Drowsiness.
• Nausea, often best managed by taking it with food.
• Blurred or double vision, especially soon after a dose.
• Mild coordination trouble.
• Headache.

Many of these ease as the body adjusts. Splitting the dose or taking it with meals often helps.

Serious side effects and warnings

Serious problems are uncommon, but two categories carry FDA boxed warnings.

Boxed warning. Carbamazepine carries FDA boxed warnings for two serious blood problems: aplastic anemia (the bone marrow stops making blood cells) and agranulocytosis (a severe drop in white blood cells that raises infection risk). Both are rare but can be life-threatening. Signs to report urgently include fever, sore throat, mouth sores, unusual bruising or bleeding, and marked fatigue. A second boxed warning covers serious skin reactions (Stevens-Johnson syndrome and toxic epidermal necrolysis), which are much more likely in people who carry the HLA-B*1502 gene variant, most common in people of Asian ancestry. Genetic testing before starting is standard for at-risk groups.

• Low sodium (SIADH). Carbamazepine can cause the body to hold onto water, dropping blood sodium. Signs include headache, confusion, weakness, and unsteadiness. Older adults are at higher risk.
• Liver injury. Rare but possible. LFTs are checked at baseline and periodically.
• Suicidal thoughts. Like other anticonvulsants, carbamazepine carries a warning about a possible small increase in suicidal thoughts. Any new or worsening thoughts of self-harm should prompt contact with the prescriber.

Sexual side effects

Carbamazepine isn't a leading cause of sexual side effects the way SSRIs and SNRIs often are. Some people report reduced desire, and because carbamazepine can affect sex hormone levels through liver enzyme induction, changes are possible. If sexual function shifts after starting it, that's worth raising with the prescriber.

Weight, appetite, and sleep

Carbamazepine is roughly weight-neutral for many people, which sets it apart from lithium and valproate. Some weight gain can happen but it isn't a prominent feature.

Its effect on sleep tilts sedating early on. Some people find that useful; others feel foggy in the morning. Taking a larger portion of the dose at night can help.

Starting and dosing basics

This section is general background, not a dosing instruction for any individual. The right dose and form are decisions for a prescriber.

Carbamazepine comes as immediate-release tablets and chewable tablets, extended-release tablets, extended-release capsules (which can be opened onto food), and an oral suspension. The ER forms allow twice-daily dosing; immediate-release forms are usually taken three or four times a day. Levels are typically checked at baseline (before starting), a few days after a dose change, and again after autoinduction settles at about 4 to 6 weeks.

Missed doses and interactions

If you miss a dose, take it when you remember unless it's close to the next scheduled dose. Don't double up.

Interactions are where carbamazepine really matters. It is a strong CYP3A4 and broad enzyme inducer, which means it lowers the blood levels (and effectiveness) of many other drugs. That list includes hormonal contraceptives, warfarin, many other antipsychotics and antidepressants, statins, some HIV medications, and immunosuppressants. Every added or dropped medication is a moment to re-check the plan.

In the other direction, some drugs raise carbamazepine levels (erythromycin, some antifungals, grapefruit juice). Alcohol adds to sedation and isn't recommended. Give every prescriber and pharmacist a full list of your medications and supplements, including over-the-counter ones.

Stopping and tapering

Stopping carbamazepine should be gradual and planned with a prescriber. An abrupt stop can destabilize mood and, in people with a seizure history, can raise seizure risk. A step-down over weeks is the safer approach.

Pregnancy and breastfeeding

Carbamazepine raises the risk of birth defects, including neural tube defects like spina bifida and craniofacial defects. It isn't as high-risk as valproate, but it's still a medication that calls for a careful conversation before any pregnancy. It also lowers the effectiveness of hormonal contraception, which matters for the same reason.

Anyone who is pregnant, planning a pregnancy, or breastfeeding should talk it through with their prescriber so alternatives can be considered.

Cost and generic availability

Carbamazepine has been available as a generic for many years and is inexpensive. Brand names include Tegretol, Tegretol XR, Carbatrol, and Equetro (the ER form specifically labeled for bipolar). Generic carbamazepine contains the same active medication and works the same way.

Common questions

Why does my dose need to go up after a few weeks? Carbamazepine speeds up its own liver processing over the first month or so. That's called autoinduction. The dose that was right at week 2 may not hold at week 6, so a re-check and adjustment is normal.

Do I really need genetic testing? If you're of Asian ancestry, yes. Carrying HLA-B*1502 raises the risk of a severe skin reaction (SJS/TEN) sharply. The test is a one-time screen and is worth doing before starting.

Will it interact with my other medications? Probably. Carbamazepine induces the liver enzymes that process many drugs, so it can lower the effectiveness of hormonal birth control, blood thinners, and many other medications. Every added or removed drug is worth reviewing.

Does it cause weight gain? Not as prominently as lithium or valproate. Some weight change can happen, but it isn't a leading feature.

Is it addictive? No. Carbamazepine doesn't cause cravings or compulsive use. The body does adjust to it, which is why stopping should be gradual.

Questions to ask your prescriber

• What are we hoping this treats, and how will we know it's working?
• What lab tests do I need, and how often?
• Should I be tested for HLA-B*1502 before starting?
• With all my other medications, are any of them going to be affected by carbamazepine?
• If we decide to stop it later, how would we do that safely?

Sources

This guide draws on current prescribing information and public health references. It is reviewed for clinical accuracy and updated as guidance changes, and current as of June 8, 2026.

• U.S. Food and Drug Administration. Carbamazepine (Tegretol, Equetro) prescribing information.
• MedlinePlus, U.S. National Library of Medicine. Carbamazepine.
• National Institute of Mental Health. Mental health medications.
• American Psychiatric Association. Practice guideline for the treatment of patients with bipolar disorder.
• National Institute for Health and Care Excellence (NICE). CG185, Bipolar disorder: assessment and management.
• International Society for Bipolar Disorders (ISBD). Consensus statements on mood stabilizers.