Dosage Calculations

lil' girl, LPN · Dec 30, 2004

When you cross multiply you multiply 1 times x which is 1x and 3 times 15 which is 45. Does that clear it up?

Goes like this 1 over 15 and 3 over x if you write it down on paper it will make sense. If not I will try to explain better. Hope this helps

lil' girl, LPN · Dec 31, 2004

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.

lpnlpn, LPN · Dec 31, 2004

Love4Me said:
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?

lil' girl, LPN · Dec 31, 2004

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.

lil' girl, LPN · Dec 31, 2004

lpnlpn said:
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

lil' girl, LPN · Jan 1, 2005

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

lil' girl, LPN · Jan 2, 2005

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.

lpnlpn, LPN · Jan 2, 2005

lpnlpn said:
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

lil' girl, LPN · Jan 5, 2005

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.

lpnlpn, LPN · Jan 9, 2005

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?_________

lil' girl, LPN · Jan 9, 2005

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

Fun2, BSN, RN · Mar 18, 2005

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!!