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facilitate the passage of therapeutic quantities of drug substances through the skin and into the general circulation for their systemic effect

Transdermal drug delivery systems (TDDSs)

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668 questions
Routes of Skin Permeation
1 Transcellular route (within the lipid bilayer) 2 Intercellular route (between the lipid bilayer - polar)
Benefits of TDDS
1 Eliminates potential pain associated with injections 2 No first pass metabolism in liver 3 Eliminates gastrointestinal side effect 4 Improves patient compliance due to simpler, pain free delivery 5 Potential for home administration
Factors affecting percutaneous absorption
1) Drug concentration 2) The larger the area of application(larger TDDS), the more drug is absorbed 3 Aqueous solubility of a drug and Partition coefficient - Drugs penetrate the skin better in their un-ionized form - Nonpolar drugs penetrate lipid rich regions - Polar drugs favor transport between cells 4 Drugs with molecular weights of 100 to 800 and adequate lipid and aqueous solubility can permeate skin. The ideal molecular weight of a drug for transdermal drug delivery is believed to be 400 or less 5 Hydration of the skin generally favors percutaneous absorption. 6 Percutaneous absorption greater when thin horny layer 7 longer the medicated application contact - greater total absorption
What are the alterations of Chemical Enhancers?
1 INCREASED HYDRATION of the stratum corneum 2 A CHANGE IN TEH STRUCTURE of the lipids and lipoproteins in the intercellular channels
LIST OF skin penetration enhancers
Acetone, azone, dimethyl acetamide, dimethyl formamide, dimethyl sulfoxide (DMSO) ethanol, oleic acid, polyethylene glycol, propylene glycol, sodium lauryl sulfate
The selection of a permeation enhancer should be based on:
1 its efficacy in enhancing skin permeation 2 its dermal toxicity (low) 3 its physicochemical and biologic compatibility with the system’s other components.
A number of drugs have been the subject of iontophoretic studies, they include
Lidocaine dexamethasone amino acids, peptides insulin Verapamil Propranolol
Transdermal drug delivery systems may be constructed of a number of layers, including:
1) an occlusive backing membrane to protect the system from environmental entry and from loss of drug from the system or moisture from the skin 2) Drug reservoir or matrix system; store and release the drug at the skin-site; 3) a release liner, which is removed before application and enables drug release; 4) an adhesive layer to maintain contact with the skin after application.
TDDSs may be categorized into two types:
1 Monolithic 2 Membrane-controlled systems
With or without excess of drug In the preparation of monolithic systems, the1 __ and the 2 __ are 3 __
1 drug 2 polymer 3 dissolved or blended together, cast as the matrix, and dried BCD
Two types of Adhesive layers
1 Peripheral Adhesive 2 Face Adhesive
Design objectives of TDDS
1. Deliver the drug to the skin for percutaneous absorption at therapeutic levels at an optimal rate 2. Contain medicincal agents having the necessary physicochemical characteristics to release from the system and partition into the stratum corneum 3. Occlude the skin to ensure one way flux of the drug into the stratum corneum 4. Have a therapeutic advantage over other dosage forms and DDS 5. Not irritate or sensitize the skin 6. Adhere well to the patient's skin and have size, appearance, and site placement that encourage acceptance.
Store and release the drug at the skin-site;
Drug reservoir or matrix system
In vivo skin penetration studies may be undertaken for one or more of the following purposes:
1 To verify and quantify the cutaneous BIOAVAILABILITY of a topically applied drug. 2 To verify and quantify the systemic BIOAVAILABILITY of a transdermal drug. 3) To establish BIOEQUIVALENCE of different topical formulations of the same drug substance. 4) To determine the incidence and degree of systemic TOXICOLOGIC RISK following topical application of a specific drug or drug product. 5) To relate resultant blood levels of drug in human to systemic therapeutic effects.
IN VIVO STUDIES 1 The most relevant studies are performed in humans, however, animal models may be used insofar as they may be effective as predictors of human response. Animal models include: __ 2 Biologic samples used in drug penetration and drug absorption studies include
1 weanling pig, rhesus monkey, and hairless mouse or rat 2 skin sections, venous blood from the application site, blood from the systemic circulation, and excreta (urine, feces, and expired air).
Advantages of TDDSs
1 AVOID GASTROINTESTINAL DRUG ABSORPTION DIFFICULTIES caused by gastrointestinal pH, enzymatic activity and drug interactions with food, drink, or other orally administered drugs. 2 SUBSTITUTE FOR ORAL ADMINISTRATION of medication when that route is unsuitable, as in instances of vomiting and/or diarrhea. 3. AVOID FIRST-PASS EFFECT 4. NONINVASIVE, AVOIDING THE INCONVENIENCE OF PARENTERAL THERAPY 5. EXTENDED THERAPY WITH SINGLE APPLICATION, thereby improving patient compliance over other dosage forms requiring more frequent dose administration. 6. The activity of drugs having short half-lives is extended through the reservoir of drug present in the therapeutic delivery system and its controlled release characteristics. 7 Drug therapy may be terminated rapidly by removal of the application from the surface of the skin. 8 Ease of rapid identification of the medication in emergencies (e.g., nonresponsive, unconscious, or comatose patient) due to the physical presence of TDDS
Disadvantages of TDDSs
1. Only relatively POTENT DRUGS are suitable candidates for transdermal delivery due to the natural limits of drug entry imposed by the skin’s impermeability. 2. Some patients may develop CONTACT DERMATITIS at the site of application due to one or more of the system components, necessitating discontinuation.
Examples of transdermal drug delivery systems
1 Transdermal scopolamine 2 Transdermal Nitroglycerin 3 Transdermal clonidine 4 Transdermal Nicotine 5 Transdermal Estradiol SNCNE (SENSYA NA)
Transdermal scopolamine (Transderm-Scop) is worn in __
Hairless area behind the ear. Because of the small size of the patch, the system is unobtrusive, convenient, and well accepted by the patient.
A number of nitroglycerin-containing TDDSs have been developed: __
1 Deponit (Schwarz) 2 Minitran (3M Pharmaceuticals) 3 Nitro-Dur (Key) 4 Transderm-Nitro (Novartis) Each of these products maintains nitroglycerin drug delivery for 24 HOURS after application.
CONSTRUCTION OF NITROGLYCERIN SYSTEM 1 four-layer drug pouch system 2 thin two-layer matrix system resembling 3 Nitroglycerin TDDS should be placed in the __ 4 may increase the absorption of nitroglycerin.
. 1 Transderm-Nitro TDDS 2 Deponit TDDS 3 chest, back, upper arms, or shoulders. 4 physical exercise and elevated ambient temperatures (such as in a sauna)
The first transdermal system for hypertension, was marketed in 1985.
Catapres TTS (clonidine transdermal therapeutic system, Boehringer Ingelheim)
1 Clonidine flows in the direction of the lower concentration at a constant rate limited by a rate-controlling membrane. TRUE OR FALSE
1 TRUE The system is applied to the hairless area of intact skin on the upper outer arm or chest.
1 used as adjuncts in smoking cessation programs.
1 Nicotine TDDSs (Transdermal Nicotine)
1 Testosterone transdermal systems examples 2 Transdermal testosterone application
1 Testoderm (Alza), Androderm (SmithKline Beecham) 2 applied daily, usually in the morning to mimic endogenous testosterone release.
Other transdermal therapeutic systems
Diltiazem Isosorbide dinitrate Propranolol Nifedipine Mepindolol Verapamil
1 may vary with the site of application. (Rotating locations) 2 TDDSs should be applied to clean, dry skin that is
1 Percutaneous absorption 2 free of hair and not oily, irritated, inflamed, broken, or callused.
TDDSs should be applied to clean, dry skin that is
Free of hair and not oily, irritated, inflamed, broken, or callused.
1 for treatment in male erectile dysfunction 2 for post menopausal women
1 Urethral suppository 2 Progesterone vaginal inserts
Suppositories have been generally employed for three reasons
1. Promote defecation 2. Introduce drugs into the body 3. Treat anorectal diseases (like hemorrhoids)
DOWNSIDE OF Rectal administration
Stigma of violating patient's dignity AND aesthetics, potential rectal irritation, difficulty in titrating correct dose
Rectal administration advantages
Essential in palliative medicine Excellent dosage forms for patients who does not want to administer numerous injections daily Administered to avoid nausea and vomiting for Paediatric and hospice patients Fast onset of action
Suppositories latin and meaning
Latin: "supponere" meaning 'to place under' sub (under) ponere (to place)
Convenient form for administering topical drugs.
Medication sticks ex. Mentholatum (medicated lip stick) Oxy (acne medication)
Suppository, Insert and Stick shapes various shapes: __
1 Round oval 2 Long oval 3 Teardrop 4 Bullet 5 Tampon
1 Rectal Suppositories Length and Shape 2 Adult rectal suppositories Weight 3 What shape is mostly available in the market?
1) 32 mm (1.5 inches) in length Cylindrical, one or both ends tapered. Some are Bullet shaped, Torpedo or The Little Finger 2) about 2 grams when cocoa butter (theobroma oil) is used as a base. 3) Bullet Shaped
Vaginal Inserts shape
1 Globular 2 Oviform 3 Teardrop 4 Bullet 5 Tampon
1 Male urethral suppositories Length and Weight 2 Female urethral suppositories Length and Weight
1) 140 mm long, 4 g (Cocoa Butter is employed as base) 2) 70 mm long (half), 2 g (half)
Advantages of Rectal Administration
1. Avoidance of first-pass effect 2. Drug stability- avoiding breakdown of drugs that are susceptible to gastric degradation 3. Large dose drugs: Ability to administer somewhat large dose of drugs than oral administration 4. Irritating drugs: ability to administer drugs that have an irritating effect on the oral or GI mucosa 5. Unpleasant tasting and smelling drugs 6. Rectal route is especially useful for children 7. Patient experiencing nausea and vomiting, unconscious 8. Presence of dx of the upper GI tract that interferes drug absorptions 9. Objectional taste or odor of a drug ( impt. in children) 10. Achievement of rapid drug effect systemically (alternate to injection)
Disadvantages of Rectal Administration
1. A perceived lack of flexibility regarding dosage of commercially available suppositories in underuse and a lack of availability 2. If made on demand, may be EXPENSIVE 3. Exhibit VARIABLE EFFECTIVENESS 4. Formulations with NARROW THERAPEUTIC MARGIN, cannot be interchanged w/o risk of toxicity 5. Bullet shaped suppository after insertion can leave the anorectal site and ascend to rectostigmoid and descending colon, should not be used at bedtime 6. Defecation may interrupt the absorption process of drug, occur if drug is irritating 7. The absorbing SA of the rectum is much smaller than that of the small intestine 8. Fluid content of the rectum is much less than that of the SI, which may affect dissolution rate 9. Possibility of degradation of some drugs by the microflora present in the rectum 10. Dose of drug may be greater or less than the dose of the oral drug 11. Factors that affect rectal absorption of a drug administered in the form of suppository: a. anatomic and physiologic factors b. physicochemical factors of the drug and the base
Used to relieve constipation, as laxative
RECTAL SUPPOSITORIES FOR LOCAL EFFECT/ ACTION Ex. Dulcolax (Bisacodyl) suppositories Glycerin suppositories
Used to relieve pain, irritation, itching, and inflammation associated with hemorrhoids and other anorectal conditions example suppositories
RECTAL SUPPOSITORIES FOR LOCAL EFFECT/ ACTION ex. Hydrocortisone suppositories Mesalamine suppositories
1 Physiologic factors affecting the absorption of drugs from rectal suppositories 2 Physicochemical factors
1 Colonic content (Emptier, the more absorption), Circulation route (Avoids first pass effect), pH and lack of buffering capacity of the rectal fluids 2 Lipid-water solubility, Particle Size, Nature of the base Mnemonic: CCP, LPN
1 For systemic effect, absorption is greater in a rectum that is __ 2 They slow down rectal drug absorption
1 void or empty 2 Diarrhea, Fecal matter, Tumor growth, Tissue dehydration Mnemonics: DFTT