Solutions.

A. Number of dosage units in each dose

B. Frequency of administration

C. Clarifying instructions

2. The number of dosage units in each dose is usually specified in Arabic numerals preceded by a # sign but sometimes roman numerals are used. They may be written in either capital or small letters and precede or follow the name of the dosage form. For example,

Latin abbreviations are often used to describe the frequency of administration. Some of the commonly used abbreviations are listed in Table 4.1. Sometimes periods are omitted from the abbreviated terms.

TABLE 4.1 Some Latin abbreviations related to dosage frequency

Latin abbreviation	Meaning
ATC	around the clock
d. or d	day
h. or hr	hour(s)
q.	every
q. 4h.	every 4 hours
q.d	every day
b.i.d.	twice a day
t.i.d.	three times a day
q.i.d.	four times a day (here, “q” does not stand for “every”)
h.s.	at bedtime
stat	immediately; at once

As an example, let us consider these directions to the patient:

Sig: 1 tab q 3h [Take one (1) tablet every three (3) hours]

Sig: Chart II h.s. [Take two (2) powders at bedtime]. Notice that in this example the number of doses is given in roman numerals and the number follows the designation for the type of product.

If you need to brush up on Roman numerals go to the next frame. Otherwise, skip to frame 4.

3. The number of dosage units in each dose is usually specified in Arabic numerals but sometimes Roman numerals are used; they may be written in either capital or small letters and precede or follow the name of the dosage form. The final “i” in a Roman numeral is sometimes replaced by a “j”.

Some values for the Roman symbols of greatest interest to us:

Roman numeral	Arabic numeral
I or i	1
V or v	5
X or x	10
L	50
C	100
M	1000

Some rules that apply to Roman numerals:

(i) Repetition (2 or 3 times) of a numeral, duplicates or triplicates its value (ii = 2; XXX = 30).

(ii) Largest value numeral should always be used (XX not XVV = 20)

(iii) Roman numerals of lower value placed before a higher value numeral will be subtracted from the higher value (IV = 4).

(iv) Roman numeral of higher value followed by a lower value numeral have additive property (VI = 6, xvii = 17).

(v) For larger roman numerals, subtraction rule prevails over addition rule (XXIV = 10 + 10 + (5 − 1) = 24; MCMXCIX = 1999).

Examples:

i tab (1 tablet)

caps ii (2 capsules)

VIII gtt (8 drops)

What is meant by “chart III”?

Solution. Three powders in paper.

4. Translate each of the following signas into clear English:

A. Apply ung. b.i.d.

B. Tab II stat, tab I q 4h

C. Soak feet qid

D. i tab qd hs

E. 1–2 caps q. 8 h.

F. Chart I t.i.d.

Solutions.

A. Apply ointment twice a day.

B. Take two (2) tablets at once; then take one (1) tablet every four (4) hours.

C. Soak feet four (4) times a day.

D. Take one (1) tablet every day at bedtime.

E. Take one (1) or two (2) capsules every eight (8) hours.

F. Take one (1) powder three (3) times a day.

5. Latin abbreviations often appear in clarifying phrases in the signa. These may indicate whether the medication is to be taken before or after meals, by mouth or some other route of administration, with or without liquids, and so on. Commonly used phrases are given in Table 4.2. Sometimes, periods are omitted from the abbreviated terms.

TABLE 4.2 Selected Latin abbreviations used in the signa

Latin abbreviation or term	Meaning
c.	food; meal(s)
a.c.	before meals
p.c.	after meals
, cum	with
, sine	without
rep.	repeat
p.o., per os	by mouth
e.m.p.	in the manner prescribed
p.r.n.	as needed, when needed

An example of a signa is:

Sig: i tab pc aq [Take one (1) tablet after meals with water.]

Translate each of the following signas into clear English.

A. 1 caps t.i.d. a.c. ut. dict.

B. 1 tab

2 aspirins q 4h

C. One teaspoonful

aqua; rep. q. 2h.

D. Rub in prn pain

E. Caps II p.o. p.c. e.m.p.

F. Tab I q.i.d. p.c. & h.s.

Solutions.

A. Take one (1) capsule three (3) times a day before meals, as directed.

B. Take one (1) tablet with two (2) aspirin tablets, every four (4) hours.

C. Take one (1) teaspoonful without water. Repeat every two (2) hours.

D. Rub in as needed, to relieve pain.

E. Take two (2) capsules by mouth after meals, in the manner prescribed.

F. Take one (1) tablet four (4) times a day, after meals and at bedtime.

(If these Latin phrases are still Greek to you, review them, try the examples again or try some review problems.)

CALCULATIONS INVOLVING DOSE SIZE, NUMBER OF DOSES, AMOUNT DISPENSED, AND QUANTITY OF AN INGREDIENT

6. The size of the individual dose may be indicated by the prescriber in terms of the weight or volume of drug that the patient should obtain. However, directions put on the label for the patient must be written in such a way that they can be understood by the patient. Consider the prescription that follows:

Tetracycline caps	250 mg
Disp. caps. No. XII
Sig: 250 mg q.i.d.

This prescription calls for 12 capsules, each containing 250 mg of tetracycline. If the directions for use were translated literally as “250 mg four (4) times a day,” the patient would not know how many capsules to take. The label should read: “Take one (1) capsule four (4) times a day.”

	Penicillin V caps.	250 mg
	#24
	Sig: 250 mg q4h, 1h a.c.

How would you write the directions to the patient?

Solution. Take one (1) capsule every four (4) hours, one (1) hour before meals.

	Sulfisoxazole tabs	0.5 g
	Dispense #XLIV
	Sig: 2.0 g stat, 1.0 g t.i.d.

A. How many tablets should be dispensed?

B. How should the directions to the patient be written?

Solutions.

A. 44

B. Take four (4) tablets immediately, then two (2) tablets three (3) times a day.

8. A prescription calls for penicillin G tablets, each containing 200,000 units. The signa reads “400,000 units q.i.d. for 10 days.”

A. What directions should appear on the label?

B. How many tablets should be dispensed?

Solutions.

A. Take two (2) tablets four (4) times a day for ten (10) days.

B. 80 tablets (the patient will use 8 a day for 10 days.)

9. The prescription below is for Mr. Jones. Determine how many days the tablets will last him.

	Sulfadiazine tablets 0.5
	d.t.d. No. L
	Sig: Tabs II p.c. and h.s.

Solution. About 6 days

CALCULATION

Assuming that the patient eats 3 meals a day, he will take 8 tablets each day. Thus

10. To check the safety of a medication, the pharmacist must remember to calculate the dose of each drug being prescribed to the patient.

Aspirin	300 mg
Phenylpropanolamine hydrochloride	20 mg
Lactose qs ad	600 mg
d.t.d. caps #XXIV
Sig: II q 4h

This prescription is for an adult.

The usual dose of phenylpropanolamine hydrochloride is listed as “25 to 50 mg every 3 or 4 hours.”

Calculate the dose of phenylpropanolamine hydrochloride in the prescription and compare it with the usual dose.

Solution. Each capsule contains 20 mg of phenylpropanolamine hydrochloride. The patient is therefore taking 40 mg of this drug every 4 hours, which appears to be a satisfactory dose.

11. Consider the following prescription.

Ephedrine sulfate	0.48
Aspirin	7.2
Caffeine	0.24
Div. in caps #XXIV
Sig: Caps II q. 6h. p.r.n.

How much ephedrine sulfate will the patient be given in each dose, which consists of two capsules?

Solution. 40 mg

CALCULATION

The quantity of ephedrine sulfate in each capsule may be found by dividing the total quantity of this material by the number of capsules:

Thus two capsules will contain 40 mg.

12. Given the following, how many milligrams of hydrocortisone will the patient take each day?

	Hydrocortisone	0.6 g
	Sodium salicylate	30.0 g
	Div. in caps #LX
	Sig: caps I q 8 h.

Solution. 30 mg per day. (Each capsule contains 10 mg; 3 capsules are taken each day.)

13. Tablets, capsules, and suppositories are examples of dosage forms that comprise discrete units. When dealing with these unit dosage forms, indication of the size of a dose is a simple matter. The number of units is specified. However, such dosage forms as ointments and solutions are generally dispensed in bulk, and it becomes more difficult to measure dosage accurately.

The dosage of bulk liquids is usually given in terms of household measuring devices such as the teaspoon or tablespoon. There are no uniform, official standards to which household teaspoons are made, and a teaspoon found at home may be daintier or heftier than average. According to the official compendia, the average teaspoon holds about 5 mL, but teaspoons in use may contain 4.93 ± 0.24 mL.

In all of our calculations, we will assume that the capacities listed in Table 4.3 are correct. However, to ensure that the patient is actually receiving the intended volume, the pharmacist should give the patient an accurately calibrated measuring device each time a liquid medication is dispensed.

TABLE 4.3 Household devices used to measure liquid medication

Household measure	Nominal capacity (ml.)
1 teaspoonful (tsp)	5
1 tablespoonful (1/2 fξ) (tbsp)	15
1 glassful (8 fξ)	240

If a 10-mL dose is required, the patient should be directed to take 2 teaspoonfuls. Note that a fluidounce contains 2 tablespoonfuls or 6 teaspoonfuls.

Learn the table. Then fill in the blanks:

A. 2 fξ =_____teaspoonfuls.

B. 2 fξ =_____tablespoonfuls

C. 90 mL =_____teaspoonfuls.

D. 120 mL =_____tablespoonfuls.

E. 1 tablespoonful =_____teaspoonfuls.

Solutions.

A. 12 teaspoonfuls

B. 4 tablespoonfuls

C. 18 teaspoonfuls

D. 8 tablespoonfuls

E. 3 teaspoonfuls

14. Translate each of the following signas into clear English:

A. I tsp

aqua p.c.

B. 15 mL t.i.d. a.c.

C. 10 mL stat, 5 mL q 6h

Solutions.

A. Take one (1) teaspoonful, with water, after meals.

B. Take one (1) tablespoonful three (3) times a day, before meals.

C. Take two (2) teaspoonfuls at once, then one (1) teaspoonful every six (6) hours.

15. How many milliliters of solution should be dispensed for a 30-day supply of the following prescription?
     Tsp ii stat
     Tsp i b.i.d. d 2 et 3
     Tsp ii p.m. d 4 and thereafter.

Solution. 300 mL

CALCULATIONS

Total to be dispensed = 10 + 20 + 270 = 300 mL

16. Given the prescription,

	Tetracycline oral syrup
	Sig: tsp q.i.d. for 6 days

How many milliliters of tetracycline oral syrup should be dispensed?

Solution. 60 mL

CALCULATIONS

The directions state: “One-half (1/2) teaspoonful four (4) times a day for six (6) days.” The patient will therefore take

17. According to the following prescription, how much potassium bromide will the patient receive each day?

	Potassium bromide	5.4 g
	Aqua	30.0 mL
	Cherry syrup	qs ad 120.0 mL
	Sig: 1 tsp qid

Solution. 0.9 g

CALCULATIONS

A total of 4 teaspoonfuls, or 20 mL, of the syrup will be taken each day. The amount of potassium bromide in that quantity can be calculated in several ways. One approach is to set up a proportion, recognizing that the relative content of potassium bromide is the same in any volume of the syrup.