Chloroquine

SCOPE: malaria PROPHYLAXIS against chloroquine-sensitive Plasmodium species only — this page's primary indication. US label verbatim: 'The dosage for prophylaxis is 500 mg (= 300 mg base) administered once per week on exactly the same day of each week.' The figure is taken from the US label because the UK SPC (Avloclor) expresses the adult prophylaxis dose only as a tablet count — 'Two tablets taken once a week, on the same day each week' — and nothing in this bundle states the Avloclor tablet strength, so the UK number cannot be published. ⚠ THE TWO LABELS GIVE DIFFERENT SCHEDULES. UK SPC: 'Start one week before exposure to risk and continue until four weeks after leaving the malarious area.' US label: 'If circumstances permit, suppressive therapy should begin two weeks prior to exposure. However, failing this in adults, an initial double (loading) dose of 1 g (= 600 mg base)... may be taken in two divided doses, six hours apart. The suppressive therapy should be continued for eight weeks after leaving the endemic area.' For UK practice follow the UK SPC schedule with the dose above, and check current national malaria prophylaxis guidance — UK SPC §4.4: 'When used as malaria prophylaxis official guidelines and local information on prevalence of resistance to anti-malarial drugs should be taken into consideration.' Administration: UK SPC §4.2 — 'The dose should be taken after food.' No numeric maximum dose is stated for prophylaxis in either label, but UK SPC §4.4 warns that the magnitude of QT prolongation increases with drug concentration and 'Therefore, the recommended dose should not be exceeded'. TREATMENT (a separate indication, NOT the dose field above): the US label gives for uncomplicated chloroquine-sensitive malaria in adults 'An initial dose of 1 g salt (= 600 mg base) followed by an additional 500 mg (= 300 mg base) after six to eight hours and a single dose of 500 mg (= 300 mg base) on each of two consecutive days... a total dose of 2.5 g chloroquine phosphate or 1.5 g base in three days', and for P. vivax and P. ovale adds 'Concomitant therapy with an 8-aminoquinoline compound is necessary for treatment of the hypnozoite liver stage forms of the parasites' (the UK SPC says 'Follow with a course of treatment with primaquine if a radical cure is required').

SCOPE: malaria PROPHYLAXIS only, and both labels agree on the figure. UK SPC §4.2(b): 'Children: A single dose of 5mg chloroquine base/kg per week on the same day each week. Start one week before exposure to risk and continue until four weeks after leaving the malarious area.' US label: 'The dosage for prophylaxis is 5 mg calculated as base, per kg of body weight, administered once per week on exactly the same day of each week.' Note the figure is milligrams of chloroquine BASE, not of the phosphate salt (US label: 'Each 500 mg tablet of Chloroquine phosphate contains the equivalent of 300 mg chloroquine base'). UK SPC adds 'For practical purposes, children aged over 14 years may be treated as adults' and 'The dose given to infants and children should be calculated on their body weight and must not exceed the adult dose regardless of weight.' The UK SPC also gives an age-banded tablet table (1-4 years ½ tablet, 5-8 years 1 tablet, 9-14 years 1½ tablets) which is NOT reproduced here because the bundle never states the Avloclor tablet strength. If prophylaxis could not be started ahead of travel, the US label offers a loading option: 'in children 10 mg base/kg may be taken in two divided doses, six hours apart.' Doses are taken after food. Confirm against a children's formulary and current national malaria prophylaxis guidance before prescribing.