LESSON 1: SYSTEM OF MEASUREMENTS
Household System
1 teaspoonful (tsp)
1 dessertspoon
(dstsp)
1 tablespoonful
(tbsp)
1 fl oz
1 cup
1 teacup
1 pt
2 pt
4 qt
1 lb
°C to °F:
°F to °C:
°C to °K:
1 gal = 3785 mL
1 qt = 946 mL
1 pt = 473 mL
1 fl oz = 29.57 mL
1 fl dram = 3.69 mL
1 mL = 16.23 minims
30 mL
8 fl oz
180 mL
16 fl oz
1 quart
1 gallon
16 oz
5F = 9C + 160
9C = 5F – 160
K= C + 273.15
LESSON 2: ALIQUOT METHOD OF WEIGHING
AND MEASURING
Percentage of error- maximum potential error
multiplied by 100 and divided by the quantity
desired.
Weight
1 lb = 12 oz
1 oz = 8 drachm
1 drachm = 3 scruple
1 scruple = 20 gr
1 oz = 480 gr
Pound Ounce Drachm Scruple Grain
(oz, ℥)
(℈)
(lb)
(ʒ)
(gr)
12
96
288
5,760
1
8
1
24
3
1
480
60
20
Avoirdupois System
1 lb = 16 oz
1 oz = 437.5 gr
1 lb = 700 gr = 16 ounces
1 gr = 65 mg
1 g = 15.432 gr
1 oz = 28.4 g
1 kg= 2.2 lb
1 lb = 454 g
15 mL
1 m = 39.37 in
1 in = 2.57 cm
1 mL = 20 drop/gtt
1 ft = 12 in
1 yd = 3 ft
Apothecary System
Volume
1 gal = 4 qt
1 qt = 2 pt
1 pt = 16 fl oz
1 fl oz = 8 fl dram
1 fl dram = 60 minims
1
5 mL
10 mL
NOTE:
• weighing for prescription must be performed
at least in a Class A prescription
balance with a sensitivity requirement of 6
mg and a maximum acceptable error of 5%
(lower limit is 120 mg and upper limit is 120
g).
WEIGHING ACCURACY
-
Sensitive Requirement (SR) of a balance
must be known. 6 mg SR is usual.
Acceptable error: 5% or less
100% 𝑥 𝑆𝑅
= 𝑆𝑚𝑎𝑙𝑙𝑒𝑠𝑡 𝑞𝑡𝑦 (𝑚𝑔)
𝐴𝑐𝑐𝑒𝑝𝑡𝑎𝑏𝑙𝑒 𝑒𝑟𝑟𝑜𝑟 %
STEPS IN WEIGHING BY ALIQUOT METHOD
1. Calculate the smallest quantity.
2. Select the desired multiple. (The answer
should be equal or greater than the smallest
quantity.)
3. Add diluent. (Mixture – Drug)
COMPONENTS / PARTS OF A PRESCRIPTION
STEPS IN GETTING VOLUME BY ALIQUOT
METHOD
1. Select a multiple.
2. Add the diluent.
M2: PRESCRIPTION
- A medication order written by a physician,
dentist, or veterinary doctors.
- A formula written on a piece of paper is
called a “Prescription Blank”.
▪
▪
TYPES OF DRUGS BASED ON PRESCRIPTION
1. Prescription Drugs
-
-
Ethical or Legend drugs.
Pharmaceutical products or drug
preparation that are to be dispensed only
upon written order of a validly registered
licensed physician, dentist or veterinarian
for the management or treatment of a
condition or disease.
Identification:
o Rx Symbol
o “Foods, Drugs, Devices and
Cosmetics Act prohibits dispensing
without prescription.”
▪
▪
Prescriber’s Information
o It usually contains the name
of the physician or dentist,
his specialty, clinic address,
contact number, and clinic
schedules.
Patient’s Information
o It contains pertinent
information about the patient
such as the name, address,
sex, age and weight, and
sometimes BSA.
Date
o Prescriptions are dated at
the time they are written and
also when they are received
and filled in the pharmacy.
o Rx is dated…
▪ To check if the
patient is
complying.
▪ To establish
medication
history.
Superscription
o
2. Non-Prescription Drugs
-
Over-the-counter drugs
Pharmaceutical products or drug
preparation that can be dispensed even
without the written order of a validly
registered licensed physician, dentist, or
veterinarian for the use of consumer for the
prevention or symptomatic relief of minor or
self-limiting ailments.
3. Dangerous Drugs
-
-
-
Pharmaceutical products referring to either
prohibited or regulated drugs that require a
special prescription form usually obtained
from the Dangerous Drug Board.
Prohibited drugs
o List A drugs
o List B drugs
Regulated drugs
Identification:
o “Maybe Habit-forming”
o “Foods, Drugs, Devices and
Cosmetics Act prohibits dispensing
without valid prescription and Opium
license.”
o
▪
▪
▪
The “Rx” symbol is a Latin
verb “Recipe” meaning “take
though” or “you take”.
Historians believed that this
symbol originated from the
sign of Jupiter employed by
ancients in requesting aid for
healing.
Inscription
o The medication prescribed.
o It is the body or principal part
of the prescription order.
Subscription
o Dispensing direction to the
pharmacist.
o It contains directions to the
pharmacist for preparing and
labeling the prescription.
o It usually contains the
quantity of the medication to
be dispensed.
Transcription
o Direction for the patient.
o It is also known as
“signature” or “Signa”
meaning “mark though” or
“let it be labeled”.
o
▪
▪
The instructions are usually
written using abbreviated
forms of English or Latin
terms.
Refill Information
o If refill information is not
supplied it is generally
assuming that no refills are
authorized.
Prescriber's Signature and License
Number
o It contains the signature of
the prescriber as well as the
doctor’s license number to
his profession, PTR
(Professional Tax Receipt)
number, and sometimes S2
number.
Specific gravity- ratio of the weight of a given
substance to the weight of an equal volume of
water at a similar temperature, expressed as:
𝑊𝑒𝑖𝑔ℎ𝑡 𝑜𝑓 𝑠𝑢𝑠𝑡𝑎𝑛𝑐𝑒 (𝑔)
= 𝑉𝑜𝑙𝑢𝑚𝑒 𝑜𝑓 𝑤𝑎𝑡𝑒𝑟 (𝑚𝐿)
Specific voume- ratio of the volume of a
substance to the volume of an equal weight of
another substance taken as a standard at a similar
temperature.
=
•
𝑉𝑜𝑙𝑢𝑚𝑒 𝑜𝑓 𝑠𝑢𝑠𝑡𝑎𝑛𝑐𝑒
𝑉𝑜𝑙𝑢𝑚𝑒 𝑜𝑓𝑒𝑞𝑢𝑎𝑙 𝑤𝑒𝑖𝑔ℎ𝑡 𝑤𝑎𝑡𝑒𝑟
The specific volume and specific gravity are
reciprocals of each other, that is:
1
Specific volume= 𝑆𝑝𝑒𝑐𝑖𝑓𝑖𝑐 𝑔𝑟𝑎𝑣𝑖𝑡𝑦
MEDICATION ORDER
▪
▪
▪
Medication orders are orders for
medications by an individual authorized
to prescribe and are intended for use in
the institutional setting.
They may be written, presented orally
(by telephone) or presented
electronically (via fax or computer
network) to the pharmacist.
Medication order generally includes:
▪ Patient's information
▪ Date and time the order was
written
▪ Name of the product
▪ Product strength, dosage,
and route of administration.
▪ Prescriber’s signature
▪ Directions for the pharmacist
▪ Instructions for
administration
M3: DENSITY AND SPECIFIC GRAVITY
Density- mass per unit volume of a substance at a
fixed temperature and pressure.
- can be calculated by dividing the mass of a
substance by its volume, expressed as:
Density = Mass/Volume.
- The density of liquids is usually expressed
as grams per milliliter (g/mL).
Listed below are some substances with
corresponding specific gravities.
Some Representative Specific Gravities at 25°C
Acetone
0.79
Alcohol
0.81
Castor oil
0.96
Water
1.00
Glycerin
1.25
Syrup
1.31
Chloroform
1.47
Mercury
13.6
NOTES: PHARMCAL LEC
Broad Categories of Prescriptions
(1) Those written for a single
component or prefabricated product and not
requiring compounding
or admixture by the pharmacist
(2) Those written for more than a single component
and requiring compounding
prescriber
 Discontinued use because the patient feels better
or worse
 Economic reasons
 Absence of patient counseling
 Confusion over taking multiple medications
Advantages of e-prescription
 Reduced prescription errors due to prescription
legibility
 Concurrent software screens for drug interactions
 Reduced incidence of altered or forged
prescriptions
 Efficiency for both prescriber and pharmacist
 Convenience to the patient
Consequences of non compliance
 Worsening of the condition
 Requirement of additional and more expensive
and more
extensive treatment
 Hospitalization
 Surgical procedures
 Increased total health care cost
Use of Roman Numerals on
Prescription
 Used to designate quantities, as the;
 Quantity of medication to be dispensed and/or
 Quantity of medication to be taken by the patient
per dose
ss or ss = ½ L or l = 50
I, i, or j = 1
C or c = 100
V or v = 5
D or d = 500
X or x = 10
M or m = 1000
CALCULATION OF DOSES:
GENERAL CONSIDERATIONS
MODULE 3 LESSON 1
General Dose Calculation
Medication Scheduling and
Patient Compliance
 Medication scheduling
 Frequency (times per day) and duration (length of
treatment) of drug’s prescribed or recommended
use
 Patient Compliance
 Patient understanding and adherence to the
directions for use
 Patient Noncompliance
 Failure to comply with a practitioner’s or labeled
direction in the self-administration of any
medication
Patient Non compliance
overdosage or underdosage
inconsistent or sporadic dosing
incorrect duration of treatment
drug abuse or misadventuring with medications
Factors resulting to non compliance
 Unclear or misunderstood directions
 Undesired side effect of the drug that discourage
use
 Lack of patient confidence in the drug and/or
Dosing Options
the drug dose and the route of administration
employed.
4. The dose may be determined, in part, on the
patient’s weight, body surface area, health and
disease status, and pharmacokinetic factors.
5. Concomitant drug therapy may affect drug/dose
effectiveness.
6. A drug’s dose may produce undesired adverse
effects and may affect patient compliance.
7. Complex dosage regimens of multiple drug
therapy may affect patient compliance.
Child’s Drug Dosage
Calculations
CALCULATION OF DOSES:
Patient Parameters
MODULE 3 LESSON 2
Specific parameters used to
determine drug dosage:
1. Age
2. Weight
3. Body surface area
4. Nutritional and functional status
* Special considerations in drug dosage and
selection are to be given to pregnant and
lactatingmothers.
Pediatric patient groups
1. Neonates
2. Infant
3. Early childhood
4. Late childhood
5. Adolescence
Special Considerations in Dose
Determinations for Elderly Patients
1. Therapy is often initiated with a lower-than-usual
adult dose.
2. Dose adjustment may be required based on the
therapeutic response.
3. The patient’s physical condition may determine
Drug dosage based on weight
Drug dosage based on Body Surface Area
(BSA)
Determining Patient’s BSA
DOSING TABLE
Dosing tables are sometimes found in product
literatures for some drugs to assist the physician
and pharmacist in determining the dose according
to body weight or body surface area.
Sample dosing table
Special dosing consideration in Cancer
Chemotherapy
Cancer chemotherapy is;
➢the use of chemical drugs
❑mainstay treatment effective in widespread or
metastatic cancer
❑often administered orally, by IV injection, or by
continuous IV infusion