Download Oral Dosage of Drugs

Oral Dosage of Drugs
Chapter 10
MAT 119
Medication Administration
Medication administration is the way that a
drug is introduced into the body.
The route of administration is chosen
according to the speed of absorption
desired and the site of action of the
medication.
Some medications are formulated for a
specific route only and must be given in
that manner. It is important that medicines
be administered as directed by the
manufacturer.
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Oral Medication Administration
Oral and enteral administration require
that the medication not be destroyed by
the environment of the stomach and
digestive enzymes.
It is too slow if rapid absorption is
required, and cannot be used if the
patient is vomiting.
Rectal administration in the form of liquids
or suppositories circumvents this problem
in enteral administration.
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Oral Medications
Oral drug forms are generally the
easiest for the patient to take and the
most convenient for the nurse to
administer.
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Oral
Medications
Oral medications come in a variety of forms
Tablets
– Powered drugs compressed or molded into
solid shapes. Plain tablets may be crushed
for easier swallowing.
Scored tablets
– Have a line down the center so the tablet
can be broken into halves
– Unscored tablets should not be broken
because there is no certainty that the drug is
evenly distributed.
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Pill Cutter & Pill Crusher
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Oral Medications
Capsules
– Gelatin containers holding a drug in solid or
liquid form.
• For patients with difficulty swallowing, the nurse
can open and put the semisolid in applesauce or
custard – should check to see if medication is
available as a liquid.
– Some are enteric-coated or contain particles
of the drug that are coated to dissolve at
different times. These are long-acting and
should NOT be opened (time-release or
sustained-release). (Can not crush or open to
put in applesauce.)
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Oral Medications
• Coated tablets (film-coated)
– Smooth and easy to swallow because of
their coating. Some tablets may be
crushed.
• Enteric-coated tablets
– Dissolve in the more alkaline secretions of
the intestine rather than in the highly acidic
stomach juices.
– Reduces the chances of gastric mucosa
irritation.
– Should NOT be crushed!
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Oral Medications
Prolonged-release or extended-release
tablets
– Disintegrate more slowly and have a longer
duration of action.
– Decreases the number of doses of tablets
– Should NOT be crushed!
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Oral Medications
• Sublingual tablets
– Dissolve quickly under the tongue
– Medication is absorbed through capillaries
and reaches the circulation without passing
through the GI tract.
• Coded tablets
– Have a number or letters, or both, that
make them easily identifiable.
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• Syrups
Oral Medications
– Solutions of sugar in water that disguise the
medication’s unpleasant taste –
contraindicated in patients with DM
• Elixirs
– Clear hydro-alcoholic liquids that are
sweetened – contraindicated in patients with a
history of alcoholism
• Solutions
– Clear liquids that contain a drug dissolved in
water.
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Oral Medications
• Powders
– Dry, finely ground drugs that need to be
reconstituted (dissolved) according to
manufacturer’s instructions.
– In liquid form, becomes an oral
suspension.
– Oral antibiotics are often supplied in this
form.
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Dosage Calculations
• In dosage calculations, you need 3
pieces of information:
– The doctor’s or healthcare provider’s order
– The quantity or strength of drug on hand
– The solid or liquid form of the supply drug
• Find a method that works for you
– Three-step approach (formula method)
– Ratio/Proportion
• Expressed as ratios or fractions
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Three-Step Approach
Estimate before attempting to calculate dosage
Memorize approach
Use for every dosage calculation
D desired 
 Q (quanity)  X
H (have)
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Three-Step Approach
• D represents desired dosage or
doctor’s order
• H represents the dosage on hand per
a quantity
• Both H and Q represent the supply
dosage found on the label of the drug
available
D desired 
 Q (quanity)  X
H (have)
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Three Steps to Dosage
Calculations Formula Method
• Step 1. Convert
– Ensure all measurements are in the same
system of measurement and the same size
unit of measurement.
– If not, convert before proceeding.
• Step 2. Think
– Estimate what is a reasonable amount of
the drug to be administered.
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Three Steps to Dosage
Calculations Formula Method
Step 3. Calculate Apply the formula
D
Q  X
H
D desired 
 Q (quanity)  X
H (have)
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Ratio: Proportion
What you have : What you need
Dosage on hand = Dosage desired
Amount on hand X amount desired
Supply = Dosage
Have
X amount
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Three Step Approach
Doctor’s order:
Aricept 10 mg po daily
• Convert
– No conversion is necessary. Units are in same
system (metric) and the same size (mg).
• Think
– Wanting to give 10 mg and you have 5 mg in each
tablet. You want to give twice the equivalent of
each tablet or 2 tablets per dose.
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Doctor’s order:
Aricept 10 mg po daily
Step 3-Calculate:
D
10mg
 1tab  2tab
Q  X
5mg
H
Ratio/Proportion:
5mg 10mg

1tab
X
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Doctor’s order:
Verapamil SR 240 mg po daily
Convert – none needed
Think – What I need is what I have
Calculate – no calculation needed
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Ordered: Flagyl 0.75 g po tid
How many tablets per dose should
be administered?
Convert
Think
Calculate
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Ordered: Flagyl 0.75 g po tid
How many tablets per dose should
be administered?
Convert: 0.75 g to mg = 750 mg
Think: Am I going to give more or less
than I have on hand?
Calculate:
D
1
750 mg
Q 
x 1 tablet  1 tab
500
mg
H
2
750 mg
500 mg

 1 12 tablets
1 tab
X
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Oral Liquids
• Oral liquids are supplied in solution form
and contain a specific amount of drug in
a given amount of solution.
• The supply container label indicates the
amount of drug per 1 milliliter or per
multiple milliliters of solution.
– 10 mg per 2 mL
– 125 mg per 5 mL
– 1.2 g per 30 mL
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Doctor’s Order:
Ceclor 250 mg po q 8h
Convert
Think
Calculate
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Doctor’s Order: Ceclor 250 mg po q 8h
Convert: No Conversion necessary
Think: I need to give 2 times the amount
I have on hand
Calculate: D  Q  250 mg x 5 mL  10 mL
125 mg
H
125mg 250mg

 X  10mL
5mL
X
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Order: Potassium 40 mEq po
daily
Convert: No conversion is
necessary
Think: you want to give more
than 20 mEq, actually twice
as much.
Calculate:
D
40 mEq
Q 
x 15 mL  30 mL
20 mEq
H
20mEq 40mEq

 X  30mL
15mL
X
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Conversions
If the dosage is not in the same size unit of
measurement
You must convert to the same system or
same size units
Metric to metric is most often used
Usually go to smaller unit
Household Measurements
Convert to metric equivalents
Metric system is predominant system of
measurement for drugs
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Converting to Same System
Math Tip
– In most cases, it is more practical to
convert to smaller unit
– Usually eliminates decimal or fraction,
keeping calculation in whole numbers
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Math Tip
When solving dosage problems for
drugs supplied in tablets or capsules
– Q (quantity) is always one, because the
supply dosage is per one tablet or capsule
Q = One tablet or capsule
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Remember
Do not always rely on a formula.
Always estimate what is a reasonable
amount of the drug to be administered.
This helps to identify if the dosages
calculated are reasonable and sound.
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Problem
The physician ordered Amoxil (amoxicillin)
0.5 g p.o. q 8 h. Available is Amoxil
(amoxicillin) oral suspension 250 mg/5mL,
total volume of bottle is 180 mL.
a. How many mL of Amoxil will you
10 mL
2
administer? __________
or __________
t
b. How many full doses are available?
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______
c. If the physician’s order is for 5 days, is
this an adequate total volume?
_ Yes, 30 mL x 5days = 150 mL
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__________
Problem
The physician ordered Prozac (fluoxetine
hydrochloride) 40 mg p.o. at 0730 and
2200. Available is Prozac oral solution
of 20 mg/5mL.
a. How many mL of Prozac will you
10 mL
administer? _______________
b. If the bottle contains 120 mL, how
many days will this last?
6 days
_________________
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Problem
The order states Zithromax oral
suspension 600 mg p.o. 1 hr ac in am.
Available is Zithromax 200 mg/5 mL.
a. If breakfast is served at 0800, when
should the nurse administer the
0700
medication? ______
b. How many mL will you administer? ___
15____
mL
3
1
or ________
t________
T
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Problem
The order reads K-Lor (potassium chloride) oral
solution 60 mEq in equally divided doses p.o. tid
pc (30 min – 1 hr)
a. How many mEq should you administer per
20 mEq
dose? ___
b. If K-Lor solution is available 20 mEq/15 mL, how
many mL will you administer daily? 45 mL
c. What times would you schedule the medication
if breakfast is 0800, lunch is 1200, and dinner is
1700?
0830-0900, 1230-1300, 1730-1800