Drug Formulations and Routes of Administration Flashcards
What is formulation?
Also known as “dosage” form, it is the form in which a pharmaceutical product is presented for therapeutic use (eg tablet, cream, aerosol)
What is route of administration?
One of many ways by which a drug is delivered to the body
What factors determine the most appropriate route of administration?
- Site of action
- Symptoms (oral delivery impossible if patient vomits)
- Technical / formulation capability (tablet cannot be applied in the same kind of way as a syringe, however usually same route of administration can be used for both local and systemic delivery depending on purpose of treatment)
What is oral (enteral) administration?
Administration to or by way of the mouth
Most common route, involves swallowing the formulation into GI tract, followed by intestinal absorption of the drug
Usually for systemic drug delivery
What are the advantages of oral administration?
Non-invasive
Patient can self-administer
Simple and convenient
Economical formulation production because sterilisation is not needed
What are the disadvantages of oral administration?
Slower onset of action
High acidity in stomach and digestive enzymes in the GI tract can destroy the drug eg insulin
First-pass metabolism by the liver
Not suitable for bitter or strong smelling drugs
Not suitable for unconscious or vomiting patients
What are types of oral formulations?
Solids = tablets and capsules Liquids = syrup, elixer, and oral drops
What are tablets?
Powder containing the drug and excipients (diluents, binders, lubricants etc) compressed into a hard mass
Can be for immediate or controlled/sustained drug release
Most tablets are swallowed whole but there are also chewable, orally disintergrating or effervescent tablets
What are capsules?
Power or liquid contained in a shell made from a polymer, usually gelatin
Available as hard and soft capsules
What are the differences between the oral formulations: syrup, elixer, and oral drops?
Syrup = solution containing a high concentration of sucrose or other sugars
Elixir = Flavoured / sweetened hydroalcoholic solution
Oral drops = solution, emulsion, or suspension administered in small volumes by a suitable device (eg dropper)
In terms of liquid formulations, what is a solution?
Drugs and excipients dissolved in a solvent (water only) or a mixture of miscible solvents (eg water and ethanol)
One-phase system, homogenous
In terms of liquid formulations, what is an emulsion?
One liquid dispersed as small droplets throughout another liquid
Oil-in-water or water-in-oil
Two-phase system
In terms of liquid formulations, what is suspension?
Solid particles dispersed throughout another liquid
Solid-in-liquid
Two-phase system
What is sublingual administration?
Administration beneath the tongue
Available as sublingual tablets or sublingual sprays
What is buccal administration?
Administration directed toward the cheek, generally from within the mouth
Buccal tablet placed on the inside of the cheek between the gum and lip
What are the advantages of sublingual and buccal administration?
Good for systemic drug delivery - fast onset of action due to a high blood supply in oral mucosa, leading to rapid drug absorption, no first-pass metabolism
Sublingual / buccal tablets can be removed anytime when adverse effects occur
What are the disadvantages of sublingual and buccal administration?
Not suitable for bitter or strong smelling drugs
High molecular weight drugs (eg proteins and peptides) cannot be absorbed
What are injections / parenteral administration?
Administrations by needle
Liquid, sterile formulations
Numerous possible sites of injection depending on the treatment of purpose
What are the possible sites / depths of injections?
Intravenous - within veins (chemotherapy, antibiotics)
Intramuscular - within muscles (vaccines)
Subcutaneous - beneath the skin (insulin)
Intradermal - within the skin (allergy testing)
The angle / depth of the needle determines the route of injection. What are the correlating depths and angles?
Intramuscular = 90 deg, deepest Subcutaneous = 45 deg Intravenous = 25 deg Intradermal = 10 - 15 deg, shallowest
What are the advantages of intravenous administration?
Directly delivers the drug into systemic circulation
By definition, 100% bioavailable
Fast onset of action so valuable in an emergency, suitable for unconscious or vomiting patients
Small (several ml eg bolus) and large volumes (up to litres eg infusion) can be injected
Drug does can be controlled accurately
What are the disadvantages of intravenous administration?
Invasive, painful
Needs qualified healthcare profession to administer
Needs aseptic technique
Risky because once the drug is injected it cannot be recalled
Introduction of air (bubble) or particulate matter may cause embolism and potentially fatal
What are the advantages of intramuscular administration?
Drug absorption is more predictable, less variable, and more rapid compared to oral route due to blood vessels serving the muscles
Sustained release formulations can be injected
No first-pass metabolism
What are the disadvantages of intramuscular administration?
Invasive, painful
Needs qualified healthcare professional to administer and needs aseptic technique
Only small volumes (typically 2 - 5ml) can be injected
What are the different formulations for nasal administration?
Nasal spray, nasal ointment, or nasal powder
Good for local (eg nasal congestion or infection) or systemic (eg migraine) treatments
What are the different formulations for inhalation?
Aerosols produced from various devices
Good for local and systemic treatments
What is topical administration?
Medication applied to the skin (external body surface)
Semi-solid formulations usually only for local treatment
What are the different formulations for topical administration?
Cream = oil in water emulsion Lotion = oil in water emulsion, more runny than cream Ointment = oily, thick semisolid Gel = suspension of small particles interpenetrated by a liquid, may contain a gelling agent to promote stiffness Paste = semisolid with a high concentration of solids (20 - 50%) and stiff consistency
What is transdermal administration?
Administration through the skin to systemic circulation by diffusion
Available as transdermal patches for systemic drug delivery (eg nicotine replacement therapy)
Applied onto dry, flat skin area
What is ophthalmic administration?
Administration to the eye
Usually for local treatments
Available as eye drops or eye ointments
Formulation MUST be produced sterile
Can only use for a 28 day maximum after opening due to potential microbial contamination
What is otic / auricular administration?
Administration to the ear
Solutions or suspensions usually for local treatment (ear wax removal, ear infection)
What formulations can be administered rectally?
Solid = suppository
Liquid = enema
Semi-solid = cream, ointment, foam enema
Used for local (constipation, haemorrhoids) or systemic (fever, comiting) treatments
What are the advantages of rectal administration?
Suitable when oral route cannot be used (Nausea, vomiting, GI problems, post-operative, unconscious)
Suitable for drugs that cannot be orally delivered (Adverse GI effects, unpleasant taste, prone to degradation in GI tract, extensive first-pass metabolism)
What are the disadvantages of rectal administration?
Poor compliance, inconvenience
Absorption is slow and prone to high variability (presence of faeces)
Some drugs can cause local irritation of rectal mucosa, causes bowel evacuation
What administrations can be administered vaginally?
Vaginal creams and suppositories for local treatment
