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Thread: Mg/Kg ?

  1. #1
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    Mg/Kg ?

    I've seen the Mg/Kg notation used when it comes to describing a
    dosage of medication. I'm familiar with the term "mg" meaning miligrams of dosage, but do not understand the 'Kg' part.
    I've always thought that Kg meant kilograms (used in Europe) and thought that it is a measure of weight equaling 2.2 U.S. pounds - "Kilos".Over there they say a man weighs 100 kilos = 220 lbs.
    When a dosage says 5mg/kg - 4 x day, does that mean 5 miligrams
    per kilo (2.2 lbs) of the person's weight?
    If I weigh 100 kilos will I get 500 mgs per dose?
    I'm sorry if I'm asking a really dumb question.
    I am not familiar with these terms yet, being fairly new to all of this.
    Any response would be appreciated.
    Bob B
    SCI - Parent

  2. #2

    i think so

    i would understand it like that if i'd read it on medication here in italy

  3. #3
    i have never seen a prescription written that way in the usa.
    i cant imagine someone is leaving it up to the patient to figure out what the dose is
    cauda equina

  4. #4
    I believe you're correct; that is mg of medication per kg of body mass.
    Daniel

  5. #5
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    An example was posted here by Dr Young:

    The standard recommended protocol for methylprednisolone is a single bolus of 30 mg/kg of methylprednisolone given intravenously followed by 23 hours of 5.4 mg/kg/hour. The treatment should be started as soon as possible after injury and should not be used if the therapy cannot be started within 8 hours after injury.

    So that is exactly why I was asking, because I didn't understand what they gave to my son when he fractued C-5, or how much.
    Bob B
    SCI - Parent

  6. #6
    oh OK, i was thinking that you had a prescription that had that written on it. by the time it reached the hands of the layperson , everything should be figured out.
    i was imagining a 88 year old person trying to figure out the correct dosage using the unfamiliar metric system.
    cauda equina

  7. #7
    Here's how I would interpret the example you quoted:
    A 154 lb (70 kg) patient would receive 2100 mg (70 kg x 30 mg/kg) in a single initial dose, followed by a steady drip supplying 378 mg (70 kg x 5.4 mg/kg) each hour (confirmation by nurse or Dr?).

    (...that would be an 11 stone British patient)

    - Richard
    Last edited by rfbdorf; 11-30-2006 at 02:38 AM.

  8. #8
    Correct. This type of dosage is done for many drugs such as IV chemotherapy, IV antibiotics, IV cardiac drugs and many pediatric IV drugs. A prescription for drugs you take yourself would never be written this way. It is the way a nurse/pharmacist/physician would write the dosage based on protocols and drug kinetics, as with the methylprednisilone example above. It is mg. (milligrams) or ug. (micrograms) of drug per Kg. (kilogram) generally. If it is given over time (vs. a one time dose) then a time factor would be included such as the 5.4 mg./Kg./hour that Dr. Young mentioned.

    Methylprednisilone is a strong steroid that is give to reduce swelling and interrupt other aspects of the post-injury inflammatory process that can actually make the spinal cord injury worse over the first few hours. It is considered standard of care in the USA when the person has no contraindicated other injuries (such as a penetrating chest or head wound) and treatment is started within the first 8 hours after injury.

    (KLD)

  9. #9
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    Thank you for clearing that up for me
    (sorry I was so tardy getting back here to give my thanks -
    been a little busy with my son, lately)
    Bob B
    SCI - Parent

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