Dosage Forms Flashcards
What is the aim of dosage form design?
To achieve a predictable therapeutic response to a drug included in a formulation which is capable of a large scale manufacture with reproducible product quality
Am what are the eight functions of additives?
Solubilise Suspend Thicken Preserve Emulsify Modify dissolution Improve the compressibility Improve the flavor of drug substances
What are the requirement for product quality?
Chemical and physical stability Preservation against microbial contamination Uniformity of dose of drug Acceptability to users Suitable packaging and labelling
Give examples of oral dosage forms (DF)
Solutions, tablets, capsules , powders ect.
Give an example of rectal DF
Ointments, crams , powders ect.
Give examples of topical DF?
Ointments, creams , lotions, gels, solutions
Give examples of parenteral DF
Injections , implants ect.
Give examples of respiratory DF?
Aerosols , sprays , inhalations ect.
Give an example of nasal DF
Solutions, inhalations
Give an example of eye DF
Solutions , ointments , creams
Give examples of ear DF
Solutions, creams , ointments and suspensions
What are three factors to be considered before the formulation of a dosage form?
Factors affecting drug absorption from different administration routes
Drug factors such as solubility
Clinical indication and Patient factors such as age , body weight other illnesses
What issues are important to design dosage forms?
Drug absorption
Drug distribution
Metabolism
Excretion
What form must a drug be in to be absorbed via the membranes and epithelial of the skin, gastrointestinal tract and lungs into the body fluids?
Drug must be in solution form
What is the rate of diffusion influenced by?
Lipid solubility and ionisation degree of the drug
Give an example of a specialised transport mechanism
Glucose transport to the brain via the glucose receptor located on the blood brain barrier
Or
P-go protein which is an ATP-dependent efflux pump capable of transporting many drugs across cell membranes
What is first pass metabolism?
Where the concentration of s drug is greatly reduced before it reaches the systemic circulation. It is the fraction of lost drug during the process of absorption which is generally related to the liver and gut wall
Where does a drug enter once it is swallowed?
Absorbed by the digestive system and enters the hepatic portal system
Where is the drug carried after the hepatic portal system?
Through the portal vein into the liver before it reaches the rest of the body
What does the liver do in regard to drug metabolism?
It metabolizes many drugs sometimes to the extent that only a small amount of the active drug emerges from the liver to the rest of the circulatory system
What is the problem of first pass metabolism?
It greatly reduces the bioavailability of the drug
What is the bioavailable fraction determined by?
The fraction of drug that is absorbed from the GI tract and the fraction that escapes metabolism during its first pass through the liver
How may the first-pass effect be avoided?
By considering other administration for example, intravenous, intramuscular, or sublingual that avoid the first-pass effect
What must be adjusted if a different administration route is used?
The dosage
What is needed if the metabolite is inactive?
A larger oral dose is required to attain the desired therapeutic effect than with a lower dosage in a route with no first-pass effect.
Give an example of a drug with a high first pass metabolism
propranolol
What is needed if the metabolite is active?
Oral dosage must be carefully tailored to the desired therapeutic effect. First-pass metabolism in this case will result in a quicker therapeutic response than that achieved by a rout with no first-pass effect
What is the fastest to slowest in terms of onset of action?
- intra muscular injections
- buccal tablets
- capsules
- intra venous injections
- depot injections
4>1~3>2>5
How long to intra venous injections take till onset of action?
seconds
How long does intra muscular, buccal tablets, aerosols and gases take till onset of action?
minutes
How long do short- term depot injections, capsules ect. Take till onset of action?
Minutes to hours
How long do enteric-coated formulation take till onset of action?
Several hours
How long do depot-injection and implants take till onset of action?
Depot injections, implants
What are the routes of drug administration?
Oral/buccal/sublingual Respiratory route Nasal Topical route Ocular parenteral route Rectal route vaginal
What route of drug administration is the safest?
Oral route
What is absorbed by in the oral route?
Mucosa and various epithelia of GI
What is the problem with the oral route?
Slow onset of action
Risk of irregular absorption
Destruction of drugs by enzymes and secretions of the GI tract (e.g. insulin)
Where are weak acids better absorbed?
Stomach pH 1
Where are weak bases better absorbed?
In the intestine 7-8pH of the large intestine
What are the most popular oral dosage forms?
Tablets Capsules Suspensions Solutions Emulsions
What is sublingual route?
When dosage is put under the tongue
What is buccal route?
In the pouch of the cheek
Why is sublingual mucosa more permeable to the buccal mucosa?
Due to higher vascularisation and thinner epithelium (rapid onset of action)
What are problems of sublingual route?
Cannot be used for systemic transmucosal drug administration due to the wash of the area by saliva, thus there is little time for the drug to be retained at the site of action
Give an example of sublingual administrated drug?
nitriglycerin for patients with heart disease
What are general advantages of oral route of drug administration?
Non- invasive , well-accepted ,convient ,accessible
First-pass metabolism by the liver is avoided
Drugs can be given to unconscious patients
What are the advantages of sublingual routes?
Fast onset if drug action due to higher permeability
Local action of drugs
What are advantages of buccal routes?
Local and systemic effects (oral transmucosal delivery)
Suitable for proteins and peptides due to immobile mucosa and extended smooth muscle area so longer retention to the region
What are disadvantages of buccal route?
Low drug bioavailability due to low flux of the drug through the buccal mucosa due to low permeability
Why are anti-nausea medicines used via the buccal route? the dosage forms of respiratory
The nausea itself can cause swallowed tablets to be vomited and therefore rendered ineffective
What dosage forms are used for sublingual and buccal use?
Tablets
Soft gelatine capsules filled with liquid drug
What are the dosage forms of respiratory route?
aerosol, gas, inhalation to the lungs
What is the aim of the respiratory route?
For treatment od airways diseases (bronchial asthma, cystic fibrosis)
What do lungs provide?
A large surface area for drug absorption
Is first pass metabolism avoided using respiratory route?
Yes
What is aerosol?
A two-phase system of solid particles/liquid droplets dispersed in air/other gaseous phase, having small size to enable stability as a suspension.
What is the deposition of a drug/aerosol in the airway dependent on?
Physicochemical properties of the drug
The formulation
The delivery/liberating device
The patient (breathing pattern and clinical status)