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Background
Lamotrigine is an antiepileptic drug belonging in the phenyltriazine class. It is used in the treatment of both epilepsy and as a mood stabilizer in bipolar disorder. Lamotrigine is the first medication since lithium granted Food and Drug Administration (FDA) approval for the maintenance treatment of bipolar type I. It is approved for use in more than 30 countries.
Lamotrigine has relatively few side-effects and does not require laboratory monitoring. While it is indicated for epilepsy and bipolar disorders, there is evidence that lamotrigine could have some clinical efficacy in certain neuropathic pain states.
Properties and Characteristics of Lamotrigine
| Drug class | Antiepileptic drug and Triazine anticonvulsants |
| Brand Names | Lamictal |
| Synonyms | Lamotrigina, Lamotrigine, Lamotriginum |
| Molecular Formula | C9H7Cl2N5 |
| Molecular Weight | 256.09 g/mol |
| IUPAC Name | 6-(2,3-dichlorophenyl)-1,2,4-triazine-3,5-diamine |
| Structural formula of main components |  |
| Pure active ingredient | Lamotrigine |
| Appearance | White to pale cream-colored powder |
| Melting point | 216-218 °C |
| Solubility | In water, 170 mg/L at 25 °C |
| Excretion | Lamotrigine is excreted in both the urine and feces. |
| Storage | Recommended storage temperature: 2 – 8 degC Keep in a dry place |
| Available Forms | Chewable dispersible tablets, disintegrating tablets, tablets for suspension, or tablets |
| Prescription | Doctor prescription is required |
What is Lamictal (Lamotrigine) used for?
- Epilepsy
- Bipolar Disorder
- Lennox-Gastaut Syndrome
What side effects may I notice from receiving this medication?
Side effects that you should report to your care team as soon as possible:
- Allergic reactions—skin rash, itching, hives, swelling of the face, lips, tongue, or throat
- Change in vision
- Fever, neck pain or stiffness, sensitivity to light, headache, nausea, vomiting, confusion
- Heart rhythm changes—fast or irregular heartbeat, dizziness, feeling faint or lightheaded, chest pain, trouble breathing
- Infection—fever, chills, cough, or sore throat
- Liver injury—right upper belly pain, loss of appetite, nausea, light-colored stool, dark yellow or brown urine, yellowing skin or eyes, unusual weakness or fatigue
- Low red blood cell count—unusual weakness or fatigue, dizziness, headache, trouble breathing
- Rash, fever, and swollen lymph nodes
- Redness, blistering, peeling or loosening of the skin, including inside the mouth
- Thoughts of suicide or self-harm, worsening mood, or feelings of depression
- Unusual bruising or bleeding
Side effects that usually do not require medical attention (report to your care team if they continue or are bothersome):
- Diarrhea
- Dizziness
- Drowsiness
- Headache
- Nausea
- Stomach pain
- Tremors or shaking
This list may not describe all possible side effects. Call your doctor for medical advice about side effects.
Mechanism of action
The exact mechanism of action of lamotrigine is not fully elucidated, as it may exert cellular activities that contribute to its efficacy in a range of conditions. Although chemically unrelated, lamotrigine actions resemble those of phenytoin and carbamazepine, inhibiting voltage-sensitive sodium channels, stabilizing neuronal membranes, thereby modulating the release of presynaptic excitatory neurotransmitters.
Lamotrigine likely acts by inhibiting sodium currents by selective binding to the inactive sodium channel, suppressing the release of the excitatory amino acid, glutamate. The mechanism of action of lamotrigine in reducing anticonvulsant activity is likely the same in managing bipolar disorder. Studies on lamotrigine have identified its binding to sodium channels in a fashion similar to local anesthetics, which could explain the demonstrated clinical benefit of lamotrigine in some neuropathic pain states.
Lamotrigine displays binding properties to several different receptors. In laboratory binding assays, it demonstrates weak inhibitory effect on the serotonin 5-HT3 receptor. Lamotrigine also weakly binds to Adenosine A1/A2 receptors, α1/α2/β adrenergic receptors, dopamine D1/D2 receptors, GABA A/B receptors, histamine H1 receptors, κ-opioid receptor (KOR), mACh receptors and serotonin 5-HT2 receptors with an IC50>100 µM. Weak inhibitory effects were observed at sigma opioid receptors. An in vivo study revealed evidence that lamotrigine inhibits Cav2.3 (R-type) calcium currents, which may also contribute to its anticonvulsant effects.
Lamotrigine may interact with other medications
Lamotrigine oral tablet can interact with other medications, vitamins, or herbs you may be taking. An interaction is when a substance changes the way a drug works. This can be harmful or prevent the drug from working well.
To help avoid interactions, your doctor should manage all of your medications carefully. Be sure to tell your doctor about all medications, vitamins, or herbs you’re taking. To find out how this drug might interact with something else you’re taking, talk to your doctor or pharmacist.
Examples of drugs that can cause interactions with lamotrigine are listed below.
Antiseizure drugs
Taking certain other antiseizure drugs with lamotrigine can lower the level of lamotrigine in your body. This can affect how well lamotrigine works. Examples of these drugs include:
- Carbamazepine
- Phenobarbital
- Primidone
- Phenytoin
Valproate, on the other hand, can raise the level of lamotrigine in your body. This can cause increased side effects that may be dangerous.
Heart arrhythmia drug
Dofetilide is used to treat heart arrhythmias. When used with lamotrigine, the levels of dofetilide in your body may be increased. This may cause fatal arrhythmias.
HIV drugs
Taking lamotrigine with certain drugs used to treat HIV can lower the level of lamotrigine in your body. This can affect how well lamotrigine works. Examples of these drugs include:
- Lopinavir/ritonavir
- Atazanavir/ritonavir
Oral contraceptives
Taking lamotrigine with combination oral contraceptives (those that contain estrogen and progesterone) can lower the level of lamotrigine in your body. This can affect how well lamotrigine works.
Tuberculosis drug
Rifampin is used to treat tuberculosis. When used with lamotrigine, it can lower the level of lamotrigine in your body. This can affect how well lamotrigine works.
Dosing
The dose of this medicine will be different for different patients. Follow your doctor’s orders or the directions on the label. The following information includes only the average doses of this medicine. If your dose is different, do not change it unless your doctor tells you to do so.
The amount of medicine that you take depends on the strength of the medicine. Also, the number of doses you take each day, the time allowed between doses, and the length of time you take the medicine depend on the medical problem for which you are using the medicine.
For oral dosage forms (chewable dispersible tablets, disintegrating tablets, tablets for suspension, or tablets)
For treatment of bipolar disorder:
Adults not taking valproic acid (Depakote®) and not taking carbamazepine (Tegretol®), phenobarbital (Luminal®), phenytoin (Dilantin®), or primidone (Mysoline®)—At first, 25 milligrams (mg) of lamotrigine once a day for 2 weeks, then 50 mg once a day for 2 weeks. After this, your doctor may gradually increase your dose as needed. However, the dose is usually not more than 200 mg a day.
Adults taking valproic acid (Depakote®)—At first, 25 mg of lamotrigine once every other day for 2 weeks, then 25 mg once a day for 2 weeks. After this, your doctor may gradually increase your dose as needed. However, the dose is usually not more than 100 mg a day.
Adults not taking valproic acid (Depakote®) but taking carbamazepine (Tegretol®), phenobarbital (Luminal®), phenytoin (Dilantin®), or primidone (Mysoline®)—At first, 50 mg of lamotrigine once a day for 2 weeks, then a total of 100 mg divided into 2 smaller doses each day for 2 weeks. After this, your doctor may gradually increase your dose as needed. However, the dose is usually not more than 400 mg a day.
Adults who are discontinuing valproic acid (Depakote®) or discontinuing carbamazepine (Tegretol®), phenobarbital (Luminal®), phenytoin (Dilantin®), or primidone (Mysoline®)—Dose will be determined by your doctor.
Children—Use and dose must be determined by your doctor.
For treatment of epilepsy:
Adults not taking valproic acid (Depakote®) but taking carbamazepine (Tegretol®), phenobarbital (Luminal®), phenytoin (Dilantin®), or primidone (Mysoline®)—At first, 50 milligrams (mg) of lamotrigine once a day for 2 weeks, then a total of 100 mg divided into 2 smaller doses each day for 2 weeks. After this, your doctor may gradually increase your dose as needed. However, the dose is usually not more than 500 mg a day.
Adults not taking valproic acid (Depakote®), carbamazepine (Tegretol®), phenobarbital (Luminal®), phenytoin (Dilantin®), or primidone (Mysoline®)—At first, 25 mg of lamotrigine once a day for 2 weeks, then 50 mg once a day for 2 weeks. After this, your doctor may gradually increase your dose as needed. However, the dose is usually not more than 375 mg a day.
Adults taking valproic acid (Depakote®)—At first, 25 mg of lamotrigine once every other day for 2 weeks, then 25 mg once a day for 2 weeks. After this, your doctor may gradually increase your dose as needed. However, the dose is usually not more than 400 mg a day.
Adults who are discontinuing valproic acid (Depakote®) or discontinuing carbamazepine (Tegretol®), phenobarbital (Luminal®), phenytoin (Dilantin®), or primidone (Mysoline®)—Dose will be determined by your doctor.
Children 2 to 12 years of age:
Children not taking valproic acid (Depakote®) but taking carbamazepine (Tegretol®), phenobarbital (Luminal®), phenytoin (Dilantin®), or primidone (Mysoline®)— At first, 0.6 milligrams per kilogram (mg/kg) of body weight of lamotrigine divided into 2 smaller doses each day for 2 weeks, then 1.2 mg/kg of body weight divided into 2 smaller doses each day for 2 weeks. After this, your doctor may gradually increase your dose as needed. However, the dose is usually not more than 400 mg a day.
Children not taking valproic acid (Depakote®), carbamazepine (Tegretol®), phenobarbital (Luminal®), phenytoin (Dilantin®), or primidone (Mysoline®)— At first, 0.3 mg/kg of body weight of lamotrigine given in one dose or two smaller doses each day for 2 weeks, then 0.6 mg/kg of body weight divided into 2 smaller doses each day for 2 weeks. After this, your doctor may gradually increase your dose as needed. However, the dose is usually not more than 300 mg a day.
Children taking valproic acid (Depakote®)— At first, 0.15 mg/kg of body weight of lamotrigine given in one dose or two smaller doses each day for 2 weeks, then 0.3 mg/kg of body weight given in one dose or two smaller doses each day for 2 weeks. After this, your doctor may gradually increase your dose as needed. However, the dose is usually not more than 200 mg a day.
Children younger than 2 years of age—Use and dose must be determined by your doctor.
For oral dosage form (extended-release tablets)
For seizures:
Adults and children older than 13 years of age not taking valproic acid (Depakote®) but taking carbamazepine (Tegretol®), phenobarbital (Luminal®), phenytoin (Dilantin®), or primidone (Mysoline®)—At first, 50 milligrams (mg) of lamotrigine once a day for 2 weeks, then 100 mg once a day for 2 weeks. After this, your doctor may gradually increase your dose as needed. However, the dose is usually not more than 600 mg a day.
Adults and children older than 13 years of age not taking valproic acid (Depakote®), carbamazepine (Tegretol®), phenobarbital (Luminal®), phenytoin (Dilantin®), or primidone (Mysoline®)—At first, 25 mg of lamotrigine once a day for 2 weeks, then 50 mg once a day for 2 weeks. After this, your doctor may gradually increase your dose as needed. However, the dose is usually not more than 400 mg a day.
Adults and children older than 13 years of age taking valproic acid (Depakote®)—At first, 25 mg of lamotrigine once every other day for 2 weeks, then 25 mg once a day for 2 weeks. After this, your doctor may gradually increase your dose as needed. However, the dose is usually not more than 250 mg a day.
Children younger than 13 years of age—Use and dose must be determined by your doctor.
In case of emergency/overdose
In case of overdose, call your nearby poison control helpline. If the victim has collapsed, had a seizure, has trouble breathing, or can’t be awakened, immediately call emergency services.
Symptoms of overdose may include:
- Loss of balance or coordination
- Uncontrollable movements of the eyes
- Double vision
- Increased seizures
- Irregular heart beat
- Loss of consciousness
- Coma
Precautions
If you are allergic to lamotrigine or have some other reactions, inform your doctor or pharmacist before taking it. Inactive ingredients might be found in this product, triggering allergic reactions or other issues.
Tell your doctor or pharmacist about your medical history, particularly if you have kidney disease, liver disease, or a certain heart rhythm disorder (Brugada syndrome).
The drug’s side effects, especially dizziness, lack of balance, and fainting, may be more severe in older adults. These side effects can make you more vulnerable to falling or fainting.
This drug should only be taken during pregnancy if prescribed. It has the potential to hurt an unborn child. However, since untreated seizures or mental/mood disorders (such as bipolar disorder) can affect a pregnant woman and her unborn child, you should not quit taking this drug until your doctor tells you to. If you’re pregnant, speak to your doctor right away about the advantages and dangers of taking this drug during pregnancy. Since birth control pills, patches, implants, and injections cannot function when combined with this drug, talk to your doctor about other options.
This medicine will pass into breast milk and have unfavorable effects on a nursing baby. Before breastfeeding, talk to your doctor.
Lamotrigine and pregnancy
It’s not known whether lamotrigine is safe to take while pregnant. Studies* of the drug’s use in pregnancy since lamotrigine was approved for use have not shown any harm to a pregnant person or fetus.
However, based on animal studies, lamotrigine may cause harm if used in pregnancy. This is because offspring born to pregnant animals receiving the drug developed low body weight and bone problems. Keep in mind that animal studies do not always predict what happens with humans.
Tell your doctor right away if you become pregnant while taking lamotrigine. They can advise on the risks and benefits of continuing treatment with this medication.
Lamotrigine and breastfeeding
It may not be safe to take lamotrigine while breastfeeding. The drug can pass into breast milk. This could cause side effects in a child who is breastfed.
If you breastfeed while taking lamotrigine, watch the breastfed child for symptoms such as rash, drowsiness, and difficulty gaining weight. These could be symptoms of side effects from lamotrigine.
If you’re breastfeeding or planning to do so, talk with your doctor. They can tell you about the risks and benefits of taking lamotrigine while breastfeeding.
Lamotrigine and birth control
It’s not known if lamotrigine is safe to take during pregnancy. If you’re sexually active and you or your partner can become pregnant, talk with your doctor about your birth control needs while you’re using lamotrigine.
Keep in mind that lamotrigine can interact with certain birth control pills. Talk with your doctor about a birth control option that won’t interact with lamotrigine.