phentermine/topiramate

Phentermine

Absorption: Extent of absorption following oral administration unknown.

Distribution: Unknown.

Metabolism/Excretion: Metabolized by the liver.

Half-Life: 19–24 hr.

Topiramate

Absorption: 80% absorbed following oral administration.

Distribution: Unknown

Metabolism/Excretion: Not extensively metabolized. 70% excreted unchanged in urine.

Half-Life: 21 hr.

Time/Action Profile ⬆ ⬇

(weight loss)

ROUTE	ONSET	PEAK	DURATION
PO	within 8 wk	16–32 wk	unknown

Contraind./Precautions ⬆ ⬇

Contraindicated in:

Hypersensitivity/idiosyncracy to sympathomimetics (contains tartrazine);
Glaucoma;
Hyperthyroidism;
During/within 14 days of MAO inhibitors;
End-stage renal disease on dialysis;
Severe hepatic impairment;
History of suicidal thought/active suicidal ideation;
OB: Pregnancy;
Lactation: Lactation.

Use Cautiously in:

History of substance abuse;
Ketogenic diet (↑ risk of kidney stones);
Rep: Women of reproductive potential;
Pedi: Children <12 yr (safety and effectiveness not established); may ↓ vertical growth;
Geri: ↑risk of adverse effects in older adults (consider age-related ↓ in cardiac, renal, and hepatic function; concurrent chronic disease states; and medications).

Adv. Reactions/Side Effects ⬆ ⬇

CV: tachycardia, hypotension, palpitations

Derm: alopecia, ERYTHEMA MULTIFORME, oligohydrosis (↓ sweating), STEVENS-JOHNSON SYNDROME, TOXIC EPIDERMAL NECROLYSIS

EENT: acute myopia, blurred vision, eye pain, secondary angle closure glaucoma, visual field defects

Endo: hypoglycemia

F and E: hypokalemia, metabolic acidosis

GI: altered taste, constipation, dry mouth, HEPATOTOXICITY

GU: ↑serum creatinine, kidney stones

Metab: ↓growth (children)

Neuro: headache, insomnia, paresthesia, cognitive impairment, dizziness, mood disorders, SEIZURES (FOLLOWING ABRUPT DISCONTINUATION), SUICIDAL IDEATION

Misc: ALLERGIC REACTION, hyperthermia

Interactions ⬆ ⬇

Drug-drug:

↑risk of hypokalemia with non-potassium-sparing diuretics.
↑risk of CNS depression with other CNS depressants, including alcohol, some antihistamines, sedative/hypnotics, antipsychotics, and opioid analgesics; avoid concurrent use of alcohol.
Altered exposure to oral contraceptives may ↑ risk of irregular bleeding.
Carbamazepine or phenytoin may ↓ levels and effectiveness.
Concurrent use of topiramate with valproic acid may ↑ risk of hyperammonemia.
Concurrent use of topiramate with carbonic anhydrase inhibitors may ↑ risk of metabolic acidosis and kidney stones.
May ↓ levels and effectiveness of pioglitazone.

Route/Dosage ⬆ ⬇

PO (Adults ): Phentermine 3.75 mg/topiramate 23 mg once daily for 14 days; then ↑ to phentermine 7.5 mg/topiramate 46 mg once daily for 12 wk; then assess weight loss. If patient has not lost ≥3% of baseline body weight, ↑ to phentermine 11.25 mg/topiramate 69 mg once daily for 14 days; then ↑ to phentermine 15 mg/topiramate 92 mg once daily for 12 wk; then assess weight loss. If patient has not lost ≥5% of baseline body weight, discontinue therapy, as success is unlikely. Discontinuation should proceed by taking the phentermine 15 mg/topiramate 92 mg capsule every other day for 1 wk and then discontinue therapy.
PO (Children ≥12 yr): Phentermine 3.75 mg/topiramate 23 mg once daily for 14 days; then ↑ to phentermine 7.5 mg/topiramate 46 mg once daily for 12 wk; then assess BMI. If patient has not experienced a ↓ of ≥3% of baseline BMI, ↑ to phentermine 11.25 mg/topiramate 69 mg once daily for 14 days; then ↑ to phentermine 15 mg/topiramate 92 mg once daily for 12 wk; then assess BMI. If patient has not experienced a ↓ of ≥5% of baseline BMI, discontinue therapy, as success is unlikely. Discontinuation should proceed by taking the phentermine 15 mg/topiramate 92 mg capsule every other day for 1 wk and then discontinue therapy. If weight loss >2 lb/wk, consider ↓ dose.

Renal Impairment

PO (Adults and Children ≥12 yr): CCr <50 mL/min: Not to exceed phentermine 7.5 mg/topiramate 46 mg once daily.

Hepatic Impairment

PO (Adults and Children ): Moderate hepatic impairment: Not to exceed phentermine 7.5 mg/topiramate 46 mg once daily.

Availability ⬆ ⬇

(Generic available)

Capsules (contain tartrazine): phentermine 3.75 mg (immediate-release [IR])/topiramate 23 mg (extended-release [ER]) (for titration only); phentermine 7.5 mg (IR)/topiramate 46 mg (ER); phentermine 11.25 mg (IR)/topiramate 69 mg (ER) (for titration only); phentermine 15 mg (IR)/topiramate 92 mg (ER)

Assessment ⬆ ⬇

Monitor for weight loss and adjust concurrent medications (antihypertensives, antidiabetics, lipid-lowering agents) as needed. Evaluate weight loss after each 12 wk of therapy.
Monitor closely for notable changes in behavior that could indicate the emergence or worsening of suicidal thoughts or behavior or depression. Discontinue therapy if these occur.
Monitor BP and HR periodically during therapy; may cause ↑ in resting HR. May cause hypotension in patients treated with antihypertensives.

Lab Test Considerations:

Verify negative pregnancy test prior to starting therapy and monthly during therapy.
- Before starting and periodically during therapy, obtain a blood chemistry profile in all patients and blood glucose in patients with diabetes on antidiabetic medication.
- May cause hypoglycemia; monitor blood glucose closely in patients with diabetes.
- May cause metabolic acidosis; monitor serum bicarbonate before starting and periodically during therapy.
- May cause ↑ serum creatinine; peak ↑ observed after 4–8 wk of therapy. Monitor serum creatinine before and periodically during therapy; if persistent ↑ occur, ↓ dose or discontinue therapy.
- May cause hypokalemia; monitor serum potassium periodically during therapy.

Implementation ⬆ ⬇

REMS: Because of teratogenic risk, Qsymia is only available through certified pharmacies that are enrolled in the Qsymia certified pharmacy network. Information can be obtained at www.QsymiaREMS.com or by calling 1-888-998-4887.
PO: Administer once daily in the morning without regard to food. Avoid dosing in the evening; may cause insomnia.

Patient/Family Teaching ⬆ ⬇

Explain purpose and side effects of medication to patient. Advise patient to read Patient Information before starting therapy. Instruct to take as directed. If dose is missed, take at next scheduled time. Do not take two doses at the same time or extra doses. Do not stop taking without consulting health care professional. Discontinue gradually, taking one dose every other day for ≥1 wk before stopping to prevent seizures. REMS: Explain Qsymia REMS requirements to patient.
Instruct patient to notify health care professional of all Rx or OTC medications, vitamins, or herbal products being taken and consult health care professional before taking any new medications. Advise patient to avoid taking other CNS depressants, opioids, or alcohol.
Advise patient to notify health care professional if sustained periods of heart pounding or racing while at rest; severe and persistent eye pain or significant changes in vision; changes in attention, concentration, memory, or difficulty finding words; or factors that can ↑ risk of acidosis (prolonged diarrhea, surgery, high-protein/low-carbohydrate diet, concomitant medications) occur.
Inform patients and families of risk of suicidal thoughts and behavior (behavioral changes; emerging or worsening signs and symptoms of depression; unusual changes in mood; emergence of suicidal thoughts, behavior, or thoughts of self-harm). Advise that these should be reported to health care professional immediately.
May cause changes in mental performance, motor performance, or vision. Caution patients to avoid driving and other activities requiring alertness until response to medication is known.
Instruct patient to ↑ fluid intake to ↑ urinary output and ↓ risk of kidney stones.
Advise patient to monitor for ↓ sweating and ↑ body temperature during physical activity, especially in hot weather.
Rep: May cause fetal harm. Advise women of reproductive potential to use effective contraception and avoid breastfeeding during therapy. Advise patients to notify health care professional if pregnancy is planned or suspected. For patients taking combined oral contraceptives, may cause irregular bleeding and spotting; advise patient to continue oral contraceptive and notify health care professional if spotting is concerning.

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Pronunciation ⬇

Classifications ⬆ ⬇

Indications ⬆ ⬇

Action ⬆ ⬇

Pharmacokinetics ⬆ ⬇