To Pi Ram Ate

topiramate (toe pie' rah mate) Topamax Pregnancy Category C Drug class

Antiepileptic Therapeutic actions

Mechanism of action not understood; antiepileptic effects may be due to the actions of blocking sodium channels in neurons with sustained depolarization; increasing GABA activity at receptors, thus potentiating the effects of this inhibitory neurotransmitter; and blocking excitatory neurotransmitters at neuron receptor sites. Indications

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Adjunctive therapy for partial-onset seizure treatment in adults and children 2–16 yr Adjunctive therapy for seizures associated with Lennox-Gastaut syndrome in adults and children Adjunctive therapy for primary generalized tonic-clonic seizures in adults and children 2–16 yr Unlabeled uses: Cluster headaches, infantile spasms

Contraindications and cautions

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Contraindicated with hypersensitivity to any component of the drug. Use cautiously with pregnancy (use only if benefits outweigh potential risks to fetus), lactation, renal or hepatic impairment, renal stones.

Available forms

Tablets—25, 100, 200 mg; sprinkle capsules—15, 25 mg Dosages ADULTS

400 mg PO daily in 2 divided doses; begin adjustment of dose at 25–50 mg/day in the evening for wk 1; 50 mg AM and PM for wk 2; 50 mg AM and 100 mg PM for wk 3; 100 mg AM and PM for wk 4; 100 mg AM and 150 mg PM for wk 5; 150 mg AM and PM for wk 6; 150 mg AM and 200 mg PM for wk 7; and 200 mg AM and PM for wk 8 and beyond. PEDIATRIC PATIENTS 2–16 YR

5–9 mg/kg/day PO in 2 divided doses, as adjunctive therapy for Lennox-Gastaut syndrome; begin therapy at < 25 mg and increase in increments of 1–3 mg/kg/day every 1–2 wk. PATIENTS WITH RENAL OR HEPATIC IMPAIRMENT

For creatinine clearance < 70 mL/min, use one-half the usual dose; allow increased time to reach desired level. For patients with hepatic impairment, adjust slowly; monitor patient carefully. Pharmacokinetics Route Oral

Onset Rapid

Peak 2 hr

Metabolism: Hepatic; T1/2: 21 hr Distribution: Crosses placenta; enters breast milk Excretion: Urine Adverse effects

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CNS: Ataxia, somnolence, dizziness, nystagmus, nervousness, anxiety, tremor, speech impairment, paresthesias, confusion, depression GI: Nausea, dyspepsia, anorexia, vomiting GU: Dysmenorrhea Hematologic: Leukopenia Respiratory: Upper respiratory infection, pharyngitis, sinusitis Other: Fatigue, rash, acute myopia and secondary angle-closure glaucoma (pain, visual disturbances, pupil dilation, redness, increased IOP), weight loss

Interactions

Drug-drug • Increased CNS depression if taken with alcohol or CNS depressants; use extreme caution • Increased risk of renal stone development with carbonic anhydrase inhibitors • Decreased effects of hormonal contraceptives with topiramate; suggest use of barrier contraceptives instead Nursing considerations CLINICAL ALERT!

Name confusion has occurred between Topamax and Toprol-XL (metoprolol); use caution. Assessment

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History: Hypersensitivity to any component of the drug; pregnancy, lactation; renal or hepatic impairment; renal stones Physical: Skin color, lesions; orientation, affect, reflexes, vision exam; R, adventitious sounds; liver and renal function tests

Interventions

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Reduce dosage; discontinue or substitute other antiepileptic gradually; abrupt discontinuation may precipitate status epilepticus. Stop the drug immediately and arrange for appropriate consultations at first sign of blurred vision, periorbital edema, or redness. Administer with food if GI upset occurs.

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Caution patient not to chew or break tablets because of bitter taste. Have patient swallow sprinkle capsules whole or by carefully opening capsule and sprinkling onto a soft food. Swallow this immediately; do not allow it to be chewed. Encourage patients with a history of renal stone development to maintain adequate fluid intake while using this drug. Suggest using barrier contraceptives to patients taking this drug. Arrange for consultation with appropriate epilepsy support groups as needed.

Teaching points

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Take this drug exactly as prescribed. Do not break or chew tablets; they have a very bitter taste. If using sprinkle capsules, open carefully and sprinkle onto soft food and swallow immediately; do not chew. Do not discontinue this drug abruptly or change dosage except on the advice of your health care provider. Arrange for frequent check-ups to monitor your response to this drug. It is very important that you keep all appointments for check-ups. Wear a medical alert bracelet at all times so that any emergency medical personnel will know that you have epilepsy and are taking antiepileptic medication. Avoid using alcohol while you are taking this drug; serious sedation could occur. These side effects may occur: Drowsiness, dizziness, sleepiness (avoid driving or performing other tasks that require alertness; symptoms may occur initially but usually disappear with continued therapy); vision changes (avoid performing tasks that require visual acuity); GI upset (take drug with food; eat frequent small meals). Report fatigue, vision changes, speech problems, personality changes.

Adverse effects in Italic are most common; those in Bold are life-threatening.