Nursing2024 Drug Handbook

lamotrigine 843

1 week, then stop valproate completely while increasing lamotrigine by 100 mg daily every week until a dose of 500 mg daily is reached. ➤ Bipolar disorder for maintenance treat- ment to delay time to occurrence of mood episodes (depression, mania, hypomania, mixed episodes) in patients treated for acute mood episodes with standard therapy Adults: Initially, 25 mg immediate-release PO once daily for 2 weeks; then 50 mg PO once daily for 2 weeks. Dosage may then be doubled at weekly intervals, to maintenance dosage of 200 mg daily. Adults taking carbamazepine or other enzyme-inducing drugs without valproate: Initially, 50 mg immediate-release PO once daily for 2 weeks; then 100 mg daily in two divided doses for 2 weeks. Dosage is then in- creased by 100 mg weekly to maintenance dosage of 400 mg daily, given in two divided doses. Adults taking valproate: Initially, 25 mg immediate-release PO every other day for 2 weeks; then 25 mg PO once daily for 2 weeks. Dosage may then be doubled at weekly intervals to maintenance dosage of 100 mg daily. ADMINISTRATION PO • Starter and titration kits are available to provide doses consistent with recommended titration schedule for the first 5 weeks of treat- ment. • Patient may swallow chewable dispersible tablets whole, chew them, or disperse them in a small amount of water or diluted fruit juice. • If tablets are chewed, give a small amount of water or diluted fruit juice to aid in swal- lowing. • Place ODTs on the tongue and have patient move them around in the mouth. • Patient may swallow ODTs with or without water and without regard to food. • Give extended-release tablets once daily with or without food. Patient must swallow tablets whole and must not chew, crush, or divide them. ACTION Inhibits release of glutamate (an excitatory neurotransmitter) in the brain via action at voltage-sensitive sodium channels. Is a weak inhibitor of the 5-HT 3 receptor.

Route

Onset

Peak Duration

PO (immediate- release) PO (extended- release)

Unknown 1–5 hr Unknown

Unknown 4–11 hr Unknown

Half-life: 7 to 148 hours, depending on age, dosage schedule, use of other anticonvulsants, and other medical conditions.

ADVERSE REACTIONS CNS: ataxia, dizziness, drowsiness, headache, migraine, somnolence, fatigue, anxiety, ab- normal thinking, amnesia, depression, con- fusion, dysarthria, emotional lability, fever, incoordination, insomnia, irritability, hypoes- thesia, dream abnormality, malaise, pain, as- thenia, speech disorder, concentration dis- turbance, seizure exacerbation. CV: pal- pitations, chest pain, edema, hemorrhage. EENT: blurred vision, diplopia, vision ab- normality, nystagmus, rhinitis, epistaxis, dry mouth, pharyngitis, sinusitis. GI: nausea, vomiting, abdominal pain, anorexia, consti- pation, diarrhea, dyspepsia, flatulence, rectal hemorrhage, peptic ulcer. GU: amenorrhea, dysmenorrhea, urinary frequency, vagini- tis, UTI. Hematologic: lymphadenopathy. Metabolic: weight loss. Musculoskeletal: arthralgia, back pain, muscle spasm, neck pain, weakness. Respiratory: cough, dys- pnea, bronchitis, bronchospasm. Skin: rash, pruritus, dermatitis, dry skin, diaphoresis, photosensitivity. Other: infection, acciden- tal injury, flulike syndrome. INTERACTIONS Drug-drug. Acetaminophen: May decrease therapeutic effects of lamotrigine. Monitor patient. Atazanavir–ritonavir, ethosuximide, lopinavir–ritonavir, oxcarbazepine, phenobarbital, phenytoin, primidone, rifampin: May decrease lamotrigine level. Monitor patient closely; adjust lamotrigine dosage. Carbamazepine : May decrease effects of lam- otrigine while increasing toxicity of carba- mazepine. Consider alternative therapy. Ad- just doses and monitor patient. Hormonal contraceptives containing estro- gen: May decrease lamotrigine level. Adjust dosage based on individual hormonal prod- uct used. By the end of the “pill-free” week, lamotrigine level may double.

L

i Photoguide

Canada

OTC Off-label use

Do not crush *Liquid contains alcohol

Genetic