Dosage Calculations - page 2

I am in a desperate situation. I thought I was getting my calculations correctly and today I got back my math results and i got a 70% :crying2: :crying2: :crying2: I am so disappointed I dont know... Read More

  1. by   lil' girl
    The only thing I can tell you is memorize, they gave us a list of measurements and I just memorized them. Of course sometimes I have to look back, but after a while it kind of sticks in your head. And are you asking grain i ss = mg? or gram? We use g for gram.

    Anyhoo

    1gr = 60 mg so to do the proportion it would be 1gr/60mg : 1.5gr/xmg

    which would be 1x:90 and divide by 1 to get 90mg.
    Last edit by lil' girl on Dec 31, '04
  2. by   lpnlpn
    Quote from Love4Me
    Not sure if this will make sense but this is how I would calculate it:

    1 gram = 1000 mg therefore 3 grams = 3000 mg

    gr 1 = 60 mg

    (3000/60) = 50

    So the answer would be 3 g = gr 50

    Anyone feel free to correct me if I am wrong or if there is a better way of explaining it.
    thank you! now i begin to calculate dosages, help i know one formula is d/h times q but how would i set this problem up---- on hand: v-cillin k 200,000 U per 5 ml----order reads v-cillin k 300,000 U p.o. ---give?
  3. by   lil' girl
    Quote from lpnlpn
    allright i think i have that but what are the equivalents for drams to grains ex. drams 8 = grains ______? thank you so much you are a lifesaver!!!!!
    1 dram = 60gr so 8drams =480 grains

    Did they not give you a list? If not I will post what I have if you would like.
  4. by   lil' girl
    Quote from lpnlpn
    thank you! now i begin to calculate dosages, help i know one formula is d/h times q but how would i set this problem up---- on hand: v-cillin k 200,000 U per 5 ml----order reads v-cillin k 300,000 U p.o. ---give?
    Do it just like the others. You have 200,000 U per 5ml so

    200,000/5ml : 300,000/xml

    200,000x :1,500,000 and divide this by 200,000 = 7.5 ml
  5. by   lil' girl
    1 gram = 15 grains
    1 grain = 60 mg
    1 kg = 1000 g
    1 g = 1000 mg
    1mg = 1000 mcg
    1 dram = 60 grain
    1 kg = 2.2 lbs
    5cc = 1 t
    15 cc = 1/2 oz. = 1T
    30cc = 1oz. = 2T
    500cc = 16 oz. = 1pt.
    1000cc = 32 oz = 1 qt.
    1L = 1000ml
    and of course cc=ml
    and gtt=m (minim)
    1cc = 15 minim = 15 gtt
    1t = 60gtt = 60 minim = 1dram=5ml=5cc

    If there are any others you need that I didn't post let me know
  6. by   lil' girl
    That ones easy, you know that 1 gr = 60 mg so just divide sixty by 8 and you get 7.5 so you will give 1 tablet.
  7. by   lpnlpn
    Quote from lpnlpn
    how do i know to divide and not multiply or something .. the lightbulbs not coming on with this one...i don't understand how to set the problem up to work it out... could you please simplify?


    also don't mean to wear out my welcome but i am cramming and i have an i.v. problem that we haven't covered could you maybe walk me through it ...
    order: Zinacef 750 mg. in 25 ml. i.v. fluid to infuse in 20 minutes
    drop factor 60 gtts/ml
  8. by   lil' girl
    drops over time, times ml

    like this 60gtt/20min X 25 ml = First 20 goes into 20 1 time and 20 goes into 60 3 times so it is 3/1 x 25 = 75 gtt

    AS for when to divide or multiply simply if you want more you multiply and if you want less divide.
  9. by   lpnlpn
    Quote from lil' girl
    drops over time, times ml

    like this 60gtt/20min X 25 ml = First 20 goes into 20 1 time and 20 goes into 60 3 times so it is 3/1 x 25 = 75 gtt

    AS for when to divide or multiply simply if you want more you multiply and if you want less divide.

    Well thanks to you I can convert and due simple calculations but this I simply don't get HELP!!!you have tetracycline syrup 1.5 G in a (apothecary) ounce ii bottle. the order reads "tetracycline125 mg" how many ml per dose should be prepared?_______

    how many doses will be in the bottle?________





    Also The physician orders Ilosone 11mg/kg/gid. for a child that weighs 33 pounds. how many mg. should each dose contain?

    how many mg. will the child recieve in a day?

    and finally....

    the physician orders phenobarbitol 1.2 mg/20 of body weight bid. the client weighs 44 lbs. how many mg. will each dose contain?______

    how many mg. will the client recieve in a day?_________
  10. by   lil' girl
    Okay for the first question, did you write it right? Because if you are going to give 125mg why would you give ml?? Is this a trick question?? As for the second part, 1.5 g is equal to 1500 mg, so the bottle would hold 12 doses if you are giving it in mg.

    #2 First divide 33 by 2.2 to get kg, which would be 15. So if you are giving 11mg/kg the proportion would go, 11mg/1kg : xmg/15kg , 1x:165 (1times x =1x and 11 times 15 = 165) divided by 1 would equal 165mg per dose. Now qid of course means 4 time per day so multiply 165 times 4 to get 660mg per day or in a 24 hr period.

    #3 Do your proportion again (I am assuming that is 20lbs since you didn't put it)anyhoo 20lbs/1.2mg : 44lbs/xmg which would be 52.8/20 = 2.6mg and bid is twice a day so it would be 5.2mg per day

    HOpe this helps
  11. by   Fun2, RN, BSN
    I'm not sure if it will help anymore than what your book shows, but I found this website about dosage calculations:

    http://www.unc.edu/~bangel/quiz/quiz5.htm


    I feel for you all, and I'll be there soon..lol I actually took a Health Math class 13 years ago...did POORLY on it. Of course, with every class I'm retaking now, I am doing great....maturity and dedication helps! lol (At least I remember the names of things...gtt, minums, etc....but don't ask about calculations.LOL)

    (I wish I could take that Health math off my transcript, but it would take too many other classes off my transcript by utilizing the 10 year fresh start option we are offered.) ugggghhhh

    Anyway, hope that link helps someone!! GOOOOOD luck!!
  12. by   Nrs_angie
    Quote from lpnlpn
    i am having trouble converting between systems of measurement, i am trying to teach myself the conversion factor method as well as the ratio proportion method but this problem is giving me a bit of a problem the problem is ---3g=gr_____ help!

    Hello,
    I can teach you both ways. Proportions are bullcrap. They take too much time. Alot of times you can simply figure it out in your head if you know what the conversion is. But if your school is making you do proportions... this is how you do it. conversion is simple if you know the measurements...
    You should know by now that 1 gram = 15-16 grains cuz grains are not exact. 15 is an easier number to work with... so if you have 3 grams then you have 45 grains. Just multiply.

    Now here is how you do proportion: they waste your time... but sometime useful if you are just learning or have a complicated measurement.

    this is just one example: if you want another one, let me know. Hope it helps.

    1 g (gram) = (grains) gr 15 *grains is always written before the value
    so whenever you set up a proportion you do it like this
    1 g : 15 gr :: 3 g : x gr *you can put grains after the number to keep it simple
    so this is how you read a proportion
    1 gram is to 15 grains as 3 grams is to x number of grains
    now you multiple the outside numbers first
    then you multiple the inside numbers second
    so
    1x = 45
    then divide to solve for x
    so
    x = 45 / 1
    x = gr 45 * remember gr goes before the number in the final answer.
    hope that makes sense.
  13. by   Nrs_angie
    Quote from mandykal
    Im doing Pharm now and I did come across something that needed rounding and I couldn't figure out when to round. Thanks for the info...

    Here's one that I just did:

    Order: Ampicllin 500mg IM q.6h

    On hand 1g...instructions: add 3.5mL diuent



    500(D)
    1000(H) times 3.5mL(Q) = 1.75 mL rounded to 2mL
    Hello,
    I read your post and I am pretty sure that you should not round that up.
    You should keep your final answer at 1.75 mL. Because, if you are going to use a 3 mL syringe then you can easily draw up 1.75. It has a 1.5 marking and a 2 ml marking with .10 mL increments. So you would just draw up half way between 1.7 and 1.8 marking.
    I'ts not much of a difference, but when you are dealing with cardiac drugs or drugs for peds... that much could make a hell of alot of difference.
    How we were taught to round up is when doing IV drip rates... cuz obviously you cant have 31.1 drips... hehehe. You have to round that to 31 drips.
    Here is one time that you can round up...
    phenobarbital 70 mg SQ q8 h ( supplied in a 1-ml ampule containing 65 mg)
    70 mg
    65 mg x 1 mL = 14/13 when you divide it out it comes to 1.07
    you could not draw that up with one 3 mL syringe... so you would round that to 1.1 which you could draw up on a 3 ml syrninge.
    I hope this helps you.

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