RE: Can you check my math, please

[Guest guest]

You got caught up in all the other info in the problem---remember the

base question... " What is the dose in household units "

The dose is 375mg. Now you just need to figure out how many mLs that

would be, then convert the mLs to teaspoons

5ml/250mg= X/375mg

X=7.5mL

One teaspoon = 5mL so...

1tsp/5mL=X/7.5mL

X= 1.5 teaspoons

Dora

> Dear Jeanetta,

> Thank you for your help with previous calculation. Here is another

> one I have some doubts about:

>

> If a prescription reads: Amoxicillin 250mg/5ml, dispense 150ml,

> 375mg t.i.d. x 5d, what is the dose in household units?

>

> First, I found how many doses at all should be dispensed:

>

> 3doses/day X 5 days = 15 doses at all

>

> Second, I found how many mls in one dose:

>

> proportion:15 doses over 150 ml equals 1 dose over x ml. I got 10

ml

> in one dose.

>

> Finally, 10 ml equal 2 tsp.

>

> But the answer key gives 1.5 tsp. Why?

[Guest guest]

Dear Anlowe,

The moderator of this group, Dora , definitely has steered

you correctly. She ALWAYS does a great job. Thanks Dora!

I will however solve it with the same set up with the horizontal

method of ratio/proportion, since this appears to be your method of

choice:

5 ml.........X

------- = -------

250 mg......375mg

Cross Multiply:

5 x 375

--------- = X ml = 7.5 ml

250

Since One teaspoonful = 5mL

1 tsp..........X tsp

------ = --------

5 mL.........7.5 mL

1 x 7.5

------- = X = 1.5 teaspoonsful = one dose

5

So WHAT did YOU find out?

For one thing you found out that there are 150 ml in the dispensed

bottle. And that the drug is to be administered three times per day.

Lets take the 150 ml and divide it by 7.5 ml per dose and this will

tell us the number of doses in the dispensed bottle.

150 ml........7.5 ml

--------- = --------

X doses.......1 dose

150 x 1

-------- = X = 20 doses

7.5

Now how many days would this Rx or bottle last?

20 doses divided by three doses per day is equal to 6.67 days or 6

days. However the Rx says to use only 5 days worth! Which would be:

7.5 x 3 x 5 = 112.5 ml total

This means that the 150 ml is over the amount that the patient

actually needs. Therefore would be an excess of

150 - 112.5 = 37.5 ml.

I do hope that this helps you out. While Dora answered your question

perfectly, I wanted to take it to the same 'area' or concept/thought

that you had while solving the problem, even though it was

incorrect. And that concept was how long would the bottle last and

how many doses did it contain; even though the question in the

problem did not ask for this information. Since you seemed to want

to know how to solve for this, I provided this information as well.

Hope this helps you out...

Respectfully,

Jeanetta Mastron CPhT BSChem

Pharm Tech Educator

> > Dear Jeanetta,

> > Thank you for your help with previous calculation. Here is

another

> > one I have some doubts about:

> >

> > If a prescription reads: Amoxicillin 250mg/5ml, dispense 150ml,

> > 375mg t.i.d. x 5d, what is the dose in household units?

> >

> > First, I found how many doses at all should be dispensed:

> >

> > 3doses/day X 5 days = 15 doses at all

> >

> > Second, I found how many mls in one dose:

> >

> > proportion:15 doses over 150 ml equals 1 dose over x ml. I got

10

> ml

> > in one dose.

> >

> > Finally, 10 ml equal 2 tsp.

> >

> > But the answer key gives 1.5 tsp. Why?

[Guest guest]

The antibiotics for kiddos that come as powders for reconstitution come in

pre-determined sizes. The doctor wrote for the 150 ml size because it would

give more than enough medication to treat for 5 days.

If the child is getting 375 mg three times a day for 5 days, you can also do

the math as:

375 mg = 1 dose

250 mg = 5 ml

So with cross-multiply and divide, you get:

375mg/? ml = 250mg/5ml

? = 7.5 ml

7.5 ml is equal to 1 dose. So the child would be using (over the whole

course of treatment):

7.5ml/dose * 3 doses/1 day * 5 days = 112.5 ml over the whole of the

treatment.

So after the 5 days of treatment, there would still be medication left over.

Della

Cat Haven, Inc

A No-Kill Cat Rescue (501c3)

Houston, Tx

www.cat-haven.org

Can you check my math, please

Dear Jeanetta,

Thank you for your help with previous calculation. Here is another

one I have some doubts about:

If a prescription reads: Amoxicillin 250mg/5ml, dispense 150ml,

375mg t.i.d. x 5d, what is the dose in household units?

First, I found how many doses at all should be dispensed:

3doses/day X 5 days = 15 doses at all

Second, I found how many mls in one dose:

proportion:15 doses over 150 ml equals 1 dose over x ml. I got 10 ml

in one dose.

Finally, 10 ml equal 2 tsp.

But the answer key gives 1.5 tsp. Why?

[Guest guest]

Dear Anlowe,

The post below is another method of how to solve this problem. It is

presented by the site resident pharmacist: Della Hengel. We are so

very lucky to have Della to help answer questions and give advice on

this site. Thank you Della.

I do believe that the doctor ordered a 150 ml container because

he/she knew it was the smallest size available that would contain

the 112.5 ml that were needed for the 5 days of treatment. He/she

also knew that in the event that the pt were to take the remainder

of the suspension that it would not hurt the pt.

Respectfully,

Jeanetta Mastron CPhT BS Chem

Pharm Tech Educator

Founder/Owner

> The antibiotics for kiddos that come as powders for reconstitution

come in

> pre-determined sizes. The doctor wrote for the 150 ml size

because it would

> give more than enough medication to treat for 5 days.

>

> If the child is getting 375 mg three times a day for 5 days, you

can also do

> the math as:

>

> 375 mg = 1 dose

> 250 mg = 5 ml

>

> So with cross-multiply and divide, you get:

>

> 375mg/? ml = 250mg/5ml

>

> ? = 7.5 ml

>

> 7.5 ml is equal to 1 dose. So the child would be using (over the

whole

> course of treatment):

>

> 7.5ml/dose * 3 doses/1 day * 5 days = 112.5 ml over the whole of

the

> treatment.

>

> So after the 5 days of treatment, there would still be medication

left over.

>

> Della

>

>