parts of prescription, identification of medication-related problem Drug interaction, Factor affecting drug interaction, Mechanism of drug interaction

1. Dr Supriya Suman
Prescriptions

2. Agenda Style
Introduction01
Part of Prescriptions02
Legality03
Medication Related Problem04

3. Part of Prescription

4. Introduction
 Prescription is the prescriber’s written order to prepare or dispense a specific remedy - usually
medication - for the administration to a specific patient.
 On the basis of :- clinical assessments, laboratory tests, and imaging studies
 Prescriptions have legal implications, as they may indicate that the prescriber takes responsibility for the
clinical care of the patient and in particular for monitoring efficacy and safety

5. Prescription writing Steps
 Make a specific diagnosis.
 Consider the pathophysiological background of the diagnosis.
 Select a specific therapeutic objective.
 Select a drug of choice.
 Determine the appropriate dosing regimen.
 A plan for monitoring the drug’s action & determine an end point for therapy.

6. Physician
Veterinarians
Pharmacist (specialized).
Nurse Practitioners
Who can
Prescribe?
Dentist
Physician Assistants
Psychologist
Other qualified Practitioner

7. Part of Prescription
Part:1 Part:2 Part:3 Part:4
Superscription Inscription Subscription
Signatura (sig)
or transcription
.

8. SUPERSCRIPT
Date
Prescriber’s
Information
Patient’s
Information
Symbol

9. Date
Written on the prescription by prescriber.
To know when the medicines were last dispensed.
To prevent the misuse of the drug by the patients. Ex:- Narcotic drugs

10. Prescriber’s Information
Prescriber’s name
license classification( Professional degree )
Address
Office telephone / Mobile number

11. Patient’s Information (Name, Age, Sex & Address of the patient)
It helps to identify the prescription. Especially in case of children, Age & sex of the
patient helps the pharmacist to check the prescriber dose of Medication
In case, if any of this information is missing in the prescription, the same may be
included by the pharmacist after proper enquiry from the patient.

12. Symbol
 It is represented by symbol Rx
 Rx is the abbreviation of
 Latin word recipe, meaning
 ‘take thou’ or ‘You Take’.

13. Inscription
 Line below the Superscript
 Name of each drug (Generic , Brand name )
 The name of each ingredient is written on a separate along with its quantity
 Strength of each drug
 Dosage form
 Example :- tab Telma 40mg p.o 1-0-0 x 15 days

14. Subscription
 Dispensing directions to Pharmacist or Nurses
 Also the quantity to be dispensed
 Make a solution : mix & place into 30 capsules
 No of doses to be dispensed : dispense 30 tablets
 Purpose of medication: (e.g. For control of blood pressure )
EXAMPLE

15. Transcription
 It is usually written as ‘Sig’ on the prescription .
 It consist of the direction for the patient regarding the administration of the drug. (The directions should be simple
and the doses should be fewer)
 Usually the quantity of medicament or number or dosage unit to be taken, how many times in a day or at what time
it should be taken .
 Things to avoid : - Use of abbreviations or symbol
- Instruction “Take as directed”

16. Route of administration
 for oral dosage forms --- “take” or “give”
 for externally applied products --- “Apply”
 for suppositories ---- “Insert”
 for eye, ear, nose drops ---- “instill”

17. 17
Prescriber’s name license classification
(Professional degree)
Adress
Office telephone numbers
Patient’s name Date
Address
REFILL TIMES
OR
UNTIL
NO CHILD PROOF
CONTAINER
Drug name and strength
Quantity
SIG:
WARNING PRESCIBER’S
SIGNATURE
Presciber’s other
identification data

18. Prescription writing common rule
Kept simple
Abbreviations free (if necessary Latin abbreviations should be used { I provided pdf of
mn.gov})
Trailing zeros should be avoided, Leading zeros must be added
It should provide clear and specific directions

19. Error Risk of being
misread as:
Correct
.1 1 0.1
1.0 10 1
/ 1 Abandoned
10U 100 10 units
IU 10 or 14
µg mg mcg
Use leading zeros
Never use trailing zeros

20. Error Risk of being misread as:
OD (everyday) OD (right eye)
QD(every day) QID(four times a day)
qod(every-other-day) od(everyday / right eye)
qhs(once daily at bed time) qhr(every hour)

21. Drug interactions
 Definition:- Drug interaction is defined as the pharmacological activity of one drug is altered by the
concomitant administration with a food, beverage, supplement, or another drug.

22. Precipitant
The agent which precipitates such an
interaction is referred to as the
“Precipitant”.
The Drug whose Activity is effected
by such an Interaction is called as a
“Object drug.”.
Object drug

23. Type of drug
Interaction
Drug-drug interactions
Drug-food interactions
Chemical-drug interactions
Drug-laboratory test interactions
Drug-disease interactions

24. Examples
Ciprofloxacin may significantly increase the blood levels of theophylline cause Serious and
fetal reaction (Cardiac arrest, Seizure, Respiratory Failure)
Ciprofloxacin (P) + theophylline (O)
01
A single 6-ounce glass of juice can reduce levels of CYP3A4 by nearly 50% which can
enhanced blood pressure reduction, a rise in heart rate, and an increase in vasodilatory effects.
https://pubmed.ncbi.nlm.nih.gov/8665000/
Antidiabetic + Alcohol : https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6761899/
Calcium Channel Blockers + Grapefruit
03
Drug-disease interactions
fatigue, dyspnea upon exertion, bronchospasm, insomnia, impotence, and apathy
https://pulmccm.org/asthma-review/beta-blockers-safe-for-most-patients-with-asthma-
ajrccm/#:~:text=British%20guidelines%20advise%20avoiding%20beta,failure%20or%20past%
20myocardial%20infarction).
Beta blocker + Asthma / COPD
03
Drug-drug interactions
Drug-food interactions

26. Examples
tetracycline chelates the cations calcium, magnesium, aluminum
iron resulting in a cation-tetracycline complex that cannot be absorbed.
Tetracycline + Iron, Calcium, magnesium , aluminium
04
cross-react with several digoxin immunoassays at concentrations expected after therapeutic
usage of these drugs and falsely elevate or lower serum digoxin concentrations
https://reference.medscape.com/medline/abstract/18824952
digoxin immunoassays + Spironolactone
05
Chemical-drug interactions
Drug-laboratory test interactions

27. Factors contributing to drug interactions:
 Multiple drug therapy.
 Multiple prescribers.
 Multiple pharmacological effects of drug.
 Multiple diseases/predisposing illness.
 Poor patient compliance.
 Advancing age of patient.
 Drug-related factors.

28. Mechanisms of drug interactions:
Pharmaceutical interactions
Pharmacokinetic interactions
Pharmacodynamic interactions

29. Definition
Also called as incompatibility.it is a physicochemical
interaction that occous when drugs are mixed in i.v . Infusions
causing precipitation or inactivation of active principles .
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3265267/table/i0003-3006-58-1-
31-t02/
Pharmaceutical interactions
These interactions are those in which ADME properties
of the object drug is altered by the precipitant and hence
such interactions are also called as ADME interactions”.
Pharmacokinetic Interactions
Are those in which the activity of the object drug at its
site of action is altered by the precipitant. Such interactions
may be direct or indirect..
Pharmacodynamic interactions:
Do You
Know?

30. Example Pharmaceutical Interaction
Diazepam + Infusion fluid
A significant interaction exists between
diazepam and infusion fluid containers
constructed of PVC plastics. This is attributed to
absorption of the drug into the PVC matrix
Heparin / Kanamycin+ Hydrocortisone
Inactivation of Heparin / kanamycin

31. Pharmacokinetic
the excretion pattern of the object drug is
altered.
• ALTERATION IN RENAL BLOOD FLOW
• ALTERATION OF URINE PH
• COMPETITION FOR ACTIVE
SECRETIONS
• FORCED DIURESIS
Excretion interactions
Absorption interactions involve changes in
either the rate or extent of absorption.
• CHELATION
• CHANGE IN GASTROINTESTINAL
MOTLITY
• BOWEL FLORA EFFECTS
• ALTERATION OF GI PH
Drug Absorption
Commonly associated with drugs that are
bound to plasma proteins being displaced by
another drugs that bind more strongly.
• PROTEIN – BINDING DISPLACEMENT
Distribution interactions
Are those where the metabolism of the object
drug is altered.
• METABOLIC INDUCTION
• METABOLIC INHIBITION
• GENETIC POLYMORPHISM
Metabolism interactions
Online Class

32. ABSORPTION INTERACTION
CHELATION
CEPHROFLOXACINE / PENCILLAMINE /
TETRACYCLINE
+
AL, Mg, Fe, Zn & Ca Ions(ions bind with anion and
form poorly soluble salt )
FORMATION OF POORELY SOLUBLE
AND UNABSOBABLE COMPLEX WITH
SUCH HEAVY METAL IONS.
CHANGE IN GATROINTESTINAL MOTILITY
Digoxin
+
Metoclopramide
Digoxin
+
Anti- cholinergic
Increased GI transit rate
Therapeutic failure
Slow intestinal transit
Precipitate toxicity

33. ABSORPTION INTERACTION
ALTERATION OF GI PH
Sulphonamides,
Aspirin
+
Antacids / Sodium
Bicarbonate
Ketoconazole
+
PPI
ENHANCED DISSOLUTION AND
ABSORPTION RATE /
DECREASED DISOLLUTION AND
HENCE
ABSORPTION.
DECREASED
DISOLLUTION AND
HENCE
ABSORPTION.
BOWEL FLORA EFFECT
Broad – Spectrum Antibiotics
+
Oral Contracrptives / Coumarin anti – coagulants
(Vitamin K)
Lower quantity of estrogen will release , less absorbed
not work (Inhibit ovulation and prevent conception)

34. Distribution interactions
Increased clotting time. increased risk of hemorrhage
Anti coagulants + Phenylbutazone, chloralhydrate
Interaction that affect the distribution of a object drug.
Mainly Associated with drugs displaced by another drug that binds more
strongly.
Increased hypoglycemic effect
Tolbutamide + Sulphonamides

35. Are those where the
metabolism of the object
drug is altered.
Major interaction occur either by
induction or inhibition of drug
metabolism.
Continue research on CYP450
isoenzyme – understanding
Metabolism
interactions
METABOLIC INDUCTION
Corticosteroids,/ Oral Contraceptives,/Coumarins,/Phenytoin + (Anti- epileptic)
phenobarbitone/phenytoin/carbamazepine (CYP3A4) = Decreased Plasma Levels;
Decreased efficacy Of Object Drugs
Paracetamol + Isoniazid = Increase hepatotoxic activity
METABOLIC INHIBITION
Coumarins + Metranidazole/Phenyl Butazone = Increased Anti Coagulant Activity.
Alcohol + Disulphiram,/Metronidazole= Increased In Plasma Acetaldehyde Levels
GENETIC POLYMORPHISM
5mg dose of diazepam in SLOW CYP2C19 metabolizer = slow – more
sedation , extensive - anticipated

36. EXCRETION INTERACTIONS
1. Alteration in renal blood flow
2. Alteration of urine PH
3. Change in active secretions
Are these where the excretion pattern of the object drug is altered. Major
mechanisms of excretion interactions are :-
Elevated plasma levels of lithium
LITHIUM BICARBONATE + Thiazide diuretics(3)
Increased passive reabsorption of basic. increased risk of toxicity
AMPHETAMINE ANTACIDS +ACETAzZOLAMIDE (2)
Decreased renal clearance of lithium. Risk of toxicity
LITHIUM BICARBONATE + NSAIDS(1)

37. Pharmacodynamic
When effect of 1 drug prevent the
pharmacological action of another.
 Thiazide + NSAID = decrease diuretic
activity (Na and water excretion reduce )
 Metoclopramide + levodopa =
Exacerbate parkinsonian ataxia and
dyskinesia.
Pharmacological Antagonism
2 drugs with similar pharmacological action or
side effect are given together- produce an
additive effect.
 ACE inhibitor + Spironolactone =
Hyperkalaemia
 Non- reversible MAO (phenelzine) + SSRI
(sertraline) = Serotonin syndrome
Pharmacological Synergism
Online Class

38. Mrs. XYZ , Having prescription for doxycycline and quinine
she came to counselling counter of clinical pharmacist , You
asked whether XYZ is taking another medications. XYZ is
explain she is taking iron tablets each morning. What drug
counselling should clinical pharmacist give.
CASE STUDY

39. Reference:
 Ferguson R. Drug interactions. In: G Parthasarathi, editor. A Text Book of Clinical Pharmacy Practice Essential Concepts and Skills,2nd ed.
Hyderabad : University Press (India) Private Limited;2016.p. 123-31.
 Pisarik P. Blood pressure-lowering effect of adding grapefruit juice to nifedipine and terazosin in a patient with severe renovascular
hypertension. Arch Fam Med. 1996 Jul-Aug;5(7):413-6. Available from: https://pubmed.ncbi.nlm.nih.gov/8665000/
 Philip Short et al. Randomized Placebo-controlled Trial to Evaluate Chronic Dosing Effects of Propranolol in Asthma". Am J Resp Crit Car Med,
2013;Vol. 187, No. 12 , pp. 1308-1314. Available from : https://pulmccm.org/asthma-review/beta-blockers-safe-for-most-patients-with-asthma-
ajrccm/#:~:text=British%20guidelines%20advise%20avoiding%20beta,failure%20or%20past%
 Becker DE. Adverse drug interactions. Anesth Prog. 2011 Spring;58(1):31-41. doi: 10.2344/0003-3006-58.1.31. PMID: 21410363; PMCID:
PMC3265267. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3265267/

40. Thank you