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hydroxychloroquine

hydroxychloroquine (Plaquenil)

Introduction

Actions

  • inhibition of hemozoin biocrystallization, which facilitates the aggregation of cytotoxic heme which accumulates in parasites causing their death
  • increases lysosomal pH in antigen-presenting cells
  • blocks toll-like receptors (TLR) on plasmacytoid dendritic cells (PDCs)
    • by decreasing TLR signaling, reduces the activation of dendritic cells and the inflammatory process
    • inhibits stimulation of the toll-like receptor (TLR) 9 family receptors

Adverse effects

  • most common:
    • mild anorexia and nausea
    • some abdominal cramps
    • mild diarrhoea
  • other acute effects:
    • vomiting
    • headache
    • cardiac
    • HS reactions
      • erythema multiforme
      • Stevens-Johnson syndrome
      • toxic epidermal necrolysis
      • drug reaction with eosinophilia and systemic symptoms (DRESS syndrome)
      • photosensitivity
      • acute generalized exanthematous pustulosis (AGEP)
  • chronic use effects:
    • serious macular toxicity - especially if cumulative dose exceeds 1000g
    • reversible innocuous cornea verticillata or vortex keratopathy and is characterized by whorl-like corneal epithelial deposits
    • acne
    • bleaching of hair
    • mouth and eye blisters
    • blood disorders - anemia, aplastic anemia, agranulocytosis, leukopenia, and thrombocytopenia.
    • convulsions
    • neurologic effects including paralysis, nightmares, decreased reflexes, emotional effects
    • liver toxicity and possibly liver failure
    • alopecia
    • excessive skin coloring
    • vertigo, tinnitus, hearing loss
    • psoriasis and can worsen existing cases of both psoriasis and porphyria
    • weight loss

Contraindications

  • HS to 4-Aminoquinoline compounds

Special precautions

  • diabetes
  • psoriasis
  • epilepsy - seizure threshold may be reduced
  • cardiac conditions
  • pregnancy
  • lactation
  • concurrent medications which alter liver function (eg. cimetidine, digoxin)
  • enhances hypoglycemic effects of insulin and oral hypoglycemic agents
  • can increase plasma concentrations of penicillamine which may contribute to the development of severe side effects
  • neostigmine and pyridostigmine antagonize the action of hydroxychloroquine
  • drugs that prolong QT interval and other arrhythmogenic drugs
  • co-administration with other antimalarials such as mefloquine known to lower the convulsion threshold may increase risk of convulsions

Dosage and administration

  • take at least 4hrs before or after taking medications which may bind the drug such as antacids or kaolin
  • take with a meal or a glass of milk
  • One PLAQUENIL tablet contains 200 mg of hydroxychloroquine sulfate, which is equivalent to 155 mg base.
  • Do not crush or divide PLAQUENIL film-coated tablets
  • malaria prophylaxis:
    • adults: 400 mg (310 mg base) once weekly on the same day of each week starting 2 weeks prior to exposure, and continued for 4 weeks after leaving the endemic area.
    • children: 6.5 mg/kg (5 mg/kg base), not to exceed 400 mg (310 mg base), once weekly on the same day of the week starting 2 weeks prior to exposure, and continued for 4 weeks after leaving the endemic area.
  • uncomplicated malaria Rx:
    • for radical cure of P. vivax and P. malariae infections, concomitant therapy with an 8-aminoquinoline compound is necessary.
    • adults: 800 mg (620 mg base) followed by 400 mg (310 mg base) at 6 hours, 24 hours and 48 hours after the initial dose (total 2000 mg hydroxychloroquine sulfate or 1550 mg base).
    • children: 13 mg/kg (10 mg/kg base), not to exceed 800 mg (620 mg base) followed by 6.5 mg/kg (5 mg/kg base), not to exceed 400 mg (310 mg base), at 6 hours, 24 hours and 48 hours after the initial dose. PLAQUENIL film-coated tablets cannot be divided, therefore they should not be used to treat patients who weigh less than 31 kg.
    • adults: 200 to 400 mg (155 to 310 mg base) daily, administered as a single daily dose or in two divided doses
    • action of hydroxychloroquine is cumulative and may require weeks to months to achieve the maximum therapeutic effect
    • corticosteroids and salicylates may be used in conjunction with PLAQUENIL, and they can generally be decreased gradually in dosage or eliminated after a maintenance dose of PLAQUENIL has been achieved.
    • Initial adult dosage: 400 mg to 600 mg (310 to 465 mg base) daily, administered as a single daily dose or in two divided doses.
    • Do not exceed 600 mg or 6.5 mg/kg (5 mg/kg base) per day, whichever is lower, as the incidence of retinopathy has been reported to be higher when this maintenance dose is exceeded.
hydroxychloroquine.txt · Last modified: 2020/03/26 11:58 (external edit)