Routes and Formulations

Routes are classified as enteral or parenteralEnteral refers to anything involving the alimentary tract (from mouth to rectum), there are three enteral routes: oral, sublingual, and rectalAny route other than oral, sublingual, and rectal are considered parentralParenteral neans next to or beside the enteral

The route of administration of a drug can vary the way it is absorbed and distributed in the bodyDifferent dosage forms affect onset times, length of action, or concentration of a drug in the bodyDepending on the route, the drug could be absorbed and distributed in a matter of minutes, days, months

A consideration for selecting a particular route or dosage form would be what type of effect is desiredLocal effect occurs when the drug activity is at the site of administration (eye drops, nasal drops)Systemic effect occurs when the drug is introduced into the circulatory system by route of administration and carried to the site of activity

Oral Formulations

Most frequent route of administration“PO” = by mouth“SL” = under the tongue“Buccal” = in the cheek

Solid Formulations

Tablets: hard formulations in which the drug and other ingredients are machine compressed into a shapeVary in size, weight, hardness, thickness, and disintegration and dissolutionMay be sugar-coated, film-coated, multiple compresses

Solid Formulations

Capsules contain the drug and the other ingredients packaged in a gelatin shelldifferent capsule sizes hold different amounts of drug000 = 1.37 ml00 = 0.95ml

5 = 0.13ml

Some capsules contain liquids instead of powder (soft-gel capsules)

Solid Formulations

Bulk powders contain the active drug in a small powder paper or foil envelopeThe patient empties the envelope into a glass of water or juice and drinks the contents

Liquid Fomulations

Solutions are made up of one or more solvents containing one or more dissolved substancesElixirs are sweetened water and alcohol solutionsSyrups are generally sugar-based solutions which are more viscous than waterSuspensions are fomulations where the drug cannot completely dissolve in the liquid

Sublingual (SL)

This route of administration is for certain drugs where rapid action is desired (ntg)These formulations are generally fast dissolving uncoated tablets which contain highly water soluble drugsPlaced under the tongue, the tablet dissolves and the drug is absorbed quickly into the bloodstream

Rectal (PR)

Drugs administered rectally for either local effect or to bypass degradation caused by oral administrationCommon rectal forms: suppositories, solutions, and ointments

Parenteral RoutesUsed to describe drugs given by any route other than oral, sublingual, or rectalGenerally associated with drugs administered by a needleBenefits: Good for drugs that are poorly absorbed, rapid response, patient is uncooperative, unconscious, etcDisadvantage: Expensive, require skilled personnel, once administered can’t take it back, is an invasive technique

Types of Parenteral Routes

All routes have limitations: limited to solutions, suspensions, and emulsionsMust be sterile (bacteria-free)pH must be maintainedMay require buffersvolume limited

Types of Parenteral RoutesIntradermal: administered into the top layer of the skin, requires a short needleSubcutaneous: administered into the subcutaneous layer of the skin using 3/8 inch to 1 inch needleIntravenous: are administered directly into veinsIntramuscular: are administered into muscle tissue using one to one-and-a half inch needles

Intravenous FormulationsAre administered directly into a vein and therefore the blood supplyMost solutions are water based (aqueous), but they may be glycols, alcohols, or non-aqueous solventsInjectables are difficult to formulate because they must possess syringeability and injectabilitySyringeability refers to the ease with which the suspension can be drawn from a container into a syringeInjectability refers to the properties of the suspension while being injected, properties such as flow eveness, freedom from clogging, etc.

Intravenous Sites

Veins in the antecubital area (in front of the elbow)Back of the handLarger veins in the foot

DevicesSyringes: Variety of syringe size and needle sizesInfusion: gradual intravenous injection of a volume of fluid into a patient. A large volume (500ml to 1000ml) is infused at a rate like 2-3ml/minuteInfusion Pumps: Constant delivery rate, PCA (patient-controlled analgesics) are an example patients can provide either on-demand dosing or a constant infusion rate

IntramuscularIM injections are made into the muscle fibers that are under the subcutaneous layer of skinNeedles are generally 1 inch to 1.5 inches longNeedle gauge is 19 to 22 gaugePrincipal sites are the gluteal (buttock), deltoid (upper arm), and vastus lateralis (thigh) musclesInjection sites must be changed and rotatedLimited by volume 2ml (deltoid) up to 5ml (gluteus)Generally result in lower but longer lasting blood concetrations (depot)Usually injection is more painful than other routesZ-tract is a technique used for medications that stain the skin

Subcutaneous (SC, SQ)Can be used for both short term and very long term therapiesImplantation of a device beneath the surface of the skin can allow the drug to be released slowlySites are: lower abdomen, front of thigh, upper back, back of upper armSites must be rotatedMaximum amount injected is 2mlNeedles are generally 3/8 to 1 inch and 24 to 28 Gauge

IntradermalInvolve very small amounts of solution (0.1ml) Inject into the very top layer of the skinUsed for diagnostic reasons, desensitization or immunizationEffects are generally local and not systemicIntradermal injection forms a wheal (or raised blister-like area)Usual site is the forearmNeedles are generally 3/8 inches long and 23 to 26 gauge

Ophthalmic Formulations (OS, OD, OU)

Drugs are administered to the eye for local treatment of various eye conditions and for anesthesiaEye products must be manufactured to be sterile in its final container and the pH and viscosity must be carefully controlledUsually the eye can hold 7 to 10 µl Some systemic absorption can occurOphthalmic formulations occur as eye drops, eye ointments, Ocuserts

Intranasal FormulationsThe surface of the nasal cavity is very large, has a rich blood supply, and can hold about 20mlMost intranasal formulations are used for their decogestant activity on the nasal mucosaIntranasal absorption of some drugs could result in blood concentrations close to IV administrationIntranasal formulations are solutions, suspensions, sprays, aerosols, and inhalers

Inhalation FormulationsDeliver drugs to the pulmonary system (lungs)Drugs administered affect lung function: bronchodilators, steroids, antiallergicmedicationsMost of the inhalation dosage forms are aerosols that depend on the power of compressed or liquified gas to expel the drug from the containerParticle size is critical (1-10microns), if too large the drug just gets swallowed

DevicesMetered Dose Inhalers (MDI): metered valve delivers a fixed dose when the aerosol is activatedAdaptors and spacers: assist patients who cannot coordinate inspiration and activation of the aerosolPowder Inhalers: drug is supplied in a capsule, when the patient inhales the capsule is pierced and the patient inhales the powder (Rotahaler)

Dermal Formulations

Most dermal dosage forms are used for local (topical) effects on or within the skinFormulations are used as protectants, lubricants, emollients, drying agents, or for the specific effect of the drug present

FormulationsOintments (base is greasy), creams (semisolid emulsions and vanish when applied), gels (jelly-like liquid), and lotions (suspensions)Solutions (aqueous), tinctures (alcoholic), collodions (leave a protective film on the skin), liniments (alcoholic or oleaginous solutions)Pastes (stiff), powders (drug is in talcum or cornstarch), plasters (solid or semisolid adhesive masses)Transdermal patches, tapes, gauzesAerosols

Vaginal FormulationsFormulations for this route of administration are: solutions, powders for solution, ointments, creams, aerosol foams, suppositories, tablets, contraceptive sponges, and IUDspH and absorption changes within the vagina can effect drug deliveryAnother problem is Toxic Shock Syndrome