Topiramate (Topamax) Uses, Dosage, Adverse Effects

Topiramate

(to-pir′a-mate)

Topamax

Classifications: ANTICONVULSANT; GAMMA-AMINOBUTYRATE (GABA) ENHANCER

Therapeutic: ANTICONVULSANT; ANTIEPILEPTIC

Pregnancy Category: D

AVAILABILITY

Tablet; extended release capsule; sprinkle capsule

ACTION & THERAPEUTIC EFFECT

Sulfamate-substituted monosaccharide with a broad spectrum of anticonvulsant activity. Exhibits sodium channel-blocking action, as well as enhancing the ability of GABA to induce a flux of chloride ions into the neurons, thus potentiating the activity of this inhibitory neurotransmitter (GABA). Effectiveness indicated by a decrease in seizure activity.

USES

Adjunctive therapy for partialonset seizures; generalized tonicclonic seizures; migraine prophylaxis.

UNLABELED USES

Cluster headache, bulimia nervosa, neuropathic pain, infantile spasms, bipolar disorder, obesity.

CONTRAINDICATIONS

Hypersensitivity to topiramate; suicidal ideation; pregnancy (category D). Effect on labor and delivery is unknown.

CAUTIOUS USE

Moderate and severe renal impairment, hepatic impairment; COPD; chronic acidosis;

history of suicidal thoughts or psychiatric distubances; severe pulmonary disease; older adults; lactation; children younger than 2 y. Extended Release: Children younger than 6 y.

ROUTE & DOSAGE

Partial-Onset Seizures

Adult/Adolescent/Child (over 10y): PO Immediate release: Initiate with 25 mg b.i.d., increase by 25 mg/wk to efficacy PO Maintenance Dose 200–400 mg/day divided b.i.d. (max: 1600 mg/ day) PO Extended release: 50 mg daily then increase by 50 mg/wk to reach 400 mg daily

Child (2–16 y): PO Initiate with 1–3 mg/kg at bedtime × 1 wk, then increase by 1–3 mg/kg/day in 2 divided doses q1–2wk to a target range of 5–9 mg/kg/day

Generalized Tonic-Clonic Monotherapy

Adults/Adolescents/Children (over 10 y): PO Immediate release: 50 mg/day in 2 daily divided doses, taper up dose by 50 mg per wk up to 400 mg/day

Child (2–10 y): POWeight based dosing in package insert

Migraine Prophylaxis

Adult: PO Immediate release: Initiate with 25 mg b.i.d., increase by 25 mg/wk to 100 mg/day or max tolerated dose

Renal Impairment Dosage Adjustment

CrCl less than 70 mL/min: Decrease dose by 50%

ADMINISTRATION

Oral

• Make dosage increments of 50 mg at weekly intervals to the recommended dose, usually 400 mg/day.
• Do not break tablets unless absolutely necessary because of bitter taste.
• Store at 15°–30° C (59°–86° F) in a tightly closed container. Protect from light and moisture.

ADVERSE EFFECTS (≥1%)

Body as a Whole: Fatigue, speech problems, weight loss; decreased sweating and hyperthermia in children; metabolic acidosis, upper respiratory infection. CNS: Somnolence, dizziness, ataxia, psychomotor slowing, confusion, nystagmus, paresthesia, memory difficulty, difficulty concentrating, nervousness, depression, anxiety, tremor. GI: Anorexia, nausea. Special Senses: Angle closure glaucoma (rare).

INTERACTIONS

Drug: Increased CNS depression with alcohol and other CNS DEPRESSANTS; may increase phenytoin concentrations; may decrease ORAL CONTRACEPTIVE, valproate concentrations; may increase risk of kidney stone formation with other CARBONIC ANHYDRASE INHIBITORS. Carbamazepine, phenytoin, valproate may decrease topiramate concentrations. Use cautiously with metformin. Herbal: Ginkgo may decrease anticonvulsant effectiveness.

PHARMACOKINETICS

Absorption: Rapidly absorbed from GI tract; 80% bioavailability. Peak: 2 h. Distribution: 13–17% protein bound. Metabolism: Minimally metabolized in the liver. Elimination: Primarily in urine. Half-Life: 21 h.

NURSING IMPLICATIONS

Assessment & Drug Effects

• Monitor mental status and report significant cognitive impairment.
• Monitor lab tests: Periodic CBC with Hgb and Hct.

Patient & Family Education

• Do not stop drug abruptly; discontinue gradually to minimize seizures.
• To minimize risk of kidney stones, drink at least 6–8 full glasses of water each day.
• Exercise caution with potentially hazardous activities. Sedation is common, especially with concurrent use of alcohol or other CNS depressants.
• Use or add barrier contraceptive if using hormonal contraceptives.
• Be aware that psychomotor slowing and speech/language problems may develop while on topiramate therapy.
• Report adverse effects that interfere with activities of daily living.

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Ditulis oleh Unknown pada tanggal Tuesday, October 27, 2015