Chapter 7

Routes and Formulations

Routes and Formulations

• The way the body absorbs and distributes drugs varies with the route of administration.

• Drugs are contained in formulations and the route of administration is either enteral or parenteral.– Enteral – anything involving the alimentary canal

(from the mouth to the anus). Enteral routes are oral, sublingual, buccal, and rectal.

– Parenteral - any route outside the alimentary canal.

Formulations

• For each route of administration, there are various formulations used to deliver the drug.

• Different dosage forms affect onset, duration of action, and concentration of drug in the body.

• Review pages 142-143

Local or Systemic Effect

• A local effect occurs when the drug activity is at the site of administration. (eyes, ears, nose, skin).

• A systemic effect occurs when the drug is introduced into the circulatory system by any route and carried to the blood to the site of activity.

Oral Formulations

• Oral administration is the most frequently used route because they are easy to use, carry, and administer.

• The term used to specify oral administration is peroral or PO.

• Certain drugs are effected by the pH of the stomach.

Oral formulations

• Liquid oral formulations generally reach the circulatory system faster than solid dosage forms. – Disintegration and dissolution are not required

for when dosage is in a liquid form.• Disintegration- the breaking apart of a tablet into

smaller pieces.• Dissolution – when smaller pieces of disintegrated

tablet dissolve in a solution.

Solid Formulations

• Tablets • Capsules• Bulk powders• Modified release

Liquid Formulations• Solutions – a clear liquid dissolved in a solvent

(a liquid that dissolves another substance)• Aqueous solutions are the most common type

of oral solution. Water is the solvent.• Syrups – solution that is saturated with sugar.• Nonaqueous solutions – contain solvent other

than water.• Elixirs – alcohol or water based, sweetened.

Not as thick as a syrup

Liquid Formulations• Spirits – alcoholic or hydroalcoholic solution that

are usually used for flavoring but some are medicinal.

• Tinctures - alcoholic or hydroalcoholic solution. • Suspensions – solution in which the drug does not

completely dissolve in the solvent. Sweetened or flavored. Settle over time.

• Emulsions – oil and water based. An emulsifier is used to make the drugs mix.

• Gels – gelling agents are used to increase viscosity of the drug.

Sublingual Formulations• Tablets are placed under the tongue in sublingual

administration.• When the drug is released from the tablet, it is quickly

absorbed into the circulatory system since the membranes in the mouth are very thin and there is a good blood supply.

• Nitroglycerin is the best known.• Limitations to sublingual– Condition of the mouth– The patient– Unpleasant taste to hold in mouth

Buccal Formulations

• Buccal cavity are the insides of the cheek.

• Tablets and lozenges are placed in the pouch between the cheeks and the teeth to dissolve.

• Rapid absorption of drugs.

Rectal Formulations• Drugs are administered via the rectum for a local effect or

to avoid degradation after oral administration.• If oral administration is unavailable because the patient is

vomiting, unconscious, or unable to swallow oral formulations, the rectal route is an option.

• Disadvantages:– Pt’s don’t like it– Absorption is unpredictable

• Most common rectal formulations are:– Suppositories – melt when inserted– Solutions – enemas or cleansing– Ointments - local effect, hemorrhoids

Parenteral Routes of Administration

• Parenteral – a route of administration outside the alimentary tract. Alimentary - the organs from the mouth to the anus. The GI tract is a portion of the alimentary tract.

• Parenteral routes include:Intraocular Intranasal Inhalation InjectionsDermal Vaginal

Parenteral Routes

• Uses:– Oral drug is poorly absorbed or degraded by

stomach acid– Rapid drug response is desired– Uncooperative patient– Unconscious patient

Parenteral Routes of Administration

• Disadvantages:– Cost– Requires skill to administer– Can’t take it back– Risk of administration, ie. Blood clots, infection

Parenteral Routes of Administration

• Several parenteral routes require a needle and syringe.– Intravenous – injected directly into a vein– Intradermal – administered into the top layer

of the skin– Intramuscular – administered into a muscle– Subcutaneous – administered into the

subcutaneous tissue of the skin

Injection types

Intravenous Formulations

• Intravenous dosage forms are administered directly into a vein.

• It takes 20 seconds for the medication to circulate throughout the body.

• Solutions are the most common IV formulations and are aqueous (water).

Complications of IV therapy

• Thrombus – clot formation• Phlebitis – inflammation of a vein• Air embolism – air introduced into a vein• Particulate matter – small pieces of glass from

a broken vial or ampule

Intramuscular• Less hazardous than the IV route but many

people experience pain at the injection site.– Risks include: hematoma, scar formation,

embolism, cyst.• Injection site should be as far away from

major nerves to avoid nerve injury or damage.• Only 2 – 5 mL of solution can be given,

amount depended on site. Larger muscle, more medicine.

Subcutaneous

• Injection or insertion of a device beneath the surface of the skin.

• Insulin is given by the SQ route• Risks similar to IM• Maximum amount of fluid is 2 mL.

Intradermal• Small volumes that are injected into the top

layer of skin. TB test is only 0.1 mL of solution.• Intradermal injections forms a wheal, or

raised blister like area.

Ophthalmic Formulations

• Used for local treatment of the eye.• Formulations are sterile and are either

suspensions or solutions. Ointments and inserts are available.

• Disadvantages:– Loss of dose due to spillage.– Tears wash away medication– Drug can get to systemic circulation– Can be difficult to use

Intranasal Formulations

• Nasal cavity can hold about 20 mL (or 4 tsp), which is a very large surface area and has a rich blood supply.

• Primarily used for decongestant activity on the nasal mucosa.

• Blood concentrations are about equal to IV formulations.

• Route being considered for insulin delivery.

• Disadvantages– Should not be used for prolonged

periods.– Drug often swallowed because often

difficult to administer

Inhalation Formulations

• Drugs intended to reach the pulmonary system.

• Large surface area and rich blood supply, but due to inconsistencies in absorption the route is not as good as IV.

• Gaseous and anesthetics are the most important drugs given this route.

• Most dosage forms are aerosols.

Dermal Formulations• For local effects on or with in the skin.• Dosage formulations are lubricants, drying agents, protectants,

emollients, etc. and are used for a variety of skins conditions.• Some dermal dosage formulations promote percutaneous

absorption (through the skin) and used for birth control, cardiac disease, depression, smoking cessation, etc. and cause a systemic effect.

• Advantages:– ease of administration– easily removed if needed.

• Disadvantages:• absorbed amount is limited.

Vaginal Formulations

• Used generally for localized effects.• Formulations for this route are solutions,

ointments, creams, foams, suppositories, tablets, and IUD (contraceptive device).

• Disadvantages:– Variable absorption– Toxic Shock Syndrome risk – TSS is a bacterial

infection in the blood.