dichlorphenamide

Therapeutic Classification: diuretics

Pharmacologic Classification: carbonic anhydrase inhibitors

Indications ⬆ ⬇

REMS

Primary hyperkalemic periodic paralysis, primary hypokalemic periodic paralysis and similar conditions.

Action ⬆ ⬇

Inhibits renal carbonic anhydrase, resulting in self-limiting urinary excretion of sodium, potassium, bicarbonate, and water.

Therapeutic effects:

Reduced incidence/severity of muscle weakness associated with periodic paralysis.

Pharmacokinetics ⬆ ⬇

Absorption: Well absorbed following oral administration.

Distribution: Crosses the placenta.

Metabolism/Excretion: Unknown.

Half-Life: Unknown.

Time/Action Profile ⬆ ⬇

ROUTE	ONSET	PEAK	DURATION
PO	unknown	unknown	unknown

Contraind./Precautions ⬆ ⬇

Contraindicated in:

Hypersensitivity or cross-sensitivity with sulfonamides;
Hepatic insufficiency;
Severe pulmonary obstruction;
Concurrent use of high-dose aspirin.

Use Cautiously in:

Concurrent use of low-dose aspirin;
Adrenocortical excess or renal tubular acidosis (↑ risk of hypokalemia);
OB: Use during pregnancy only if potential maternal benefit justifies fetal risks;
Lactation: Safety not established in breastfeeding;
Pedi: Safety and effectiveness not established in children;
Geri: risk of falls and metabolic acidosis in older adults.

Adv. Reactions/Side Effects ⬆ ⬇

Derm: pruritus, rash, STEVENS-JOHNSON SYNDROME

EENT: pharyngolaryngeal pain

F and E: hyperchloremic non-anion gap metabolic acidosis, hypokalemia

GI: diarrhea, nausea

Hemat: APLASTIC ANEMIA, HEMOLYTIC ANEMIA, LEUKOPENIA

Metab: ↓weight

MS: arthralgia, muscle spasms/twitching

Neuro: confusion, drowsiness, dysgeusia, paresthesias, fatigue

Resp: dyspnea

Misc: ↑falls risk, HYPERSENSITIVITY REACTIONS (INCLUDING ANAPHYLAXIS)

Interactions ⬆ ⬇

Drug-drug:

↑aspirin levels/toxicity; concurrent use with high-dose aspirin may result in anorexia, lethargy, and coma and is contraindicated..
Concurrent use with antifungals, laxatives, loop diuretics, penicillin, thiazide diuretics andtheophylline may ↑ risk of hypokalemia.
Concurrent use with other drugs that cause hyperchloremic metabolic acidosis may ↑ risk and severity of metabolic acidosis.
Excretion of barbiturates, aspirin, and lithium is ↑ and may lead to ↓ effectiveness.
Excretion of amphetamine,quinidine, procainamide, and possibly tricyclic antidepressants is ↓ and may lead to toxicity.

Route/Dosage ⬆ ⬇

PO (Adults ): 50 mg once or twice daily; titrate according to response, not to exceed 200 mg/day.

Availability ⬆ ⬇

(Generic available)

Tablets: 50 mg

Assessment ⬆ ⬇

Assess patient for signs of hypokalemia (muscle weakness, malaise, fatigue, ECG changes, vomiting).
- Assess for allergy to sulfonamides. Discontinue if rash or signs and symptoms of hypersensitivity reaction (Stevens-Johnson syndrome, toxic epidermal necrolysis, fulminant hepatic necrosis, agranulocytosis, aplastic anemia, other blood dyscrasias) occur. Pulmonary involvement can occur in isolation or as part of a systemic reaction.
- Monitor for falls. Risk ↑ in older adults and at high doses. If falls occur, consider dose ↓ or discontinuation.

Lab Test Considerations:

Monitor serum potassium at baseline and periodically during therapy. If hypokalemia occurs, consider ↓ dose or discontinuing therapy.
- May cause hyperchloremic non-anion gap metabolic acidosis. Monitor serum bicarbonate at baseline and periodically during therapy. If metabolic acidosis occurs, consider ↓ dose or discontinuing therapy.

Implementation ⬆ ⬇

PO: Administer once or twice daily.

Patient/Family Teaching ⬆ ⬇

Instruct patient to take dichlorphenamide as directed.
Caution patient to discontinue therapy and notify health care professional is rash or signs and symptoms of allergic reaction occur.
Advise patient to report worsening symptoms of periodic paralysis to health care professional.
May occasionally cause drowsiness. Caution patient to avoid driving and other activities that require alertness until response to the drug is known.
Advise patient to notify health care professional of all Rx or OTC medications, vitamins, or herbal products being taken and to consult with health care professional before taking other medications, especially aspirin.
Rep: May cause fetal harm. Advise patient to notify health care professional if pregnancy is planned or suspected or if breastfeeding. Monitor newborns of mothers treated with dichlorphenamide for metabolic acidosis.

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Pronunciation ⬇

Classifications ⬆ ⬇