Pharmacology Drug Administration Routes

Drug Administration Routes

• Rate-controlled drug action: Controlled-release tablets, capsules, and suspensions allow for sustained drug release and effect.
• Topical drug action: Ointments, creams, transdermal patches, and ophthalmic, ear, and nasal preparations deliver drugs topically for localized effects.
• Rectal or vaginal administration: Suppositories insert drugs directly into the rectum or vagina.
• Injection: Injections directly deliver drugs into the bloodstream or body tissues.
• Inhalation therapy: Inhalants and inhalation aerosols administer drugs through the respiratory system.

Solubility and Dissolution

• Solubility: The maximum concentration of a solute that can dissolve in a solvent at a given temperature.
• Factors affecting solubility:
  • Solubilizing agent/salt form: Using different solvents or salt forms can increase solubility.
  • Temperature: Most substances dissolve better at higher temperatures.
  • Particle size: Finer particles dissolve faster due to larger surface area.
  • Agitation: Stirring or shaking enhances the dissolving process.
  • pH: Solubility of weak acids and bases is influenced by the pH of the solution.
• Dissolution: The process of a solute dispersing in a solvent to form a solution. It's a kinetic process unlike solubility.

Oral Solutions

• Properties:
  • Palatable: Solutions should be pleasant in taste, appearance, and odor.
  • Stability: Solutions must remain stable over time to ensure accurate dosing.
  • Effective: Solutions must be effective when taken, considering absorption and other factors.
• Dry Mixtures for Solution:
  • Some medications are unstable in liquid form and are provided as dry powders or granules for reconstitution with water before dispensing.
• Pharmacist's Role:
  • Dispensing commercially prepared solutions.
  • Diluting solutions for pediatric use.
  • Reconstituting dry powder mixtures.
  • Compounding solutions from raw materials.
• Storage and Mixing Advice:
  • Pharmacists should advise patients on proper use, dosage, administration, and storage of oral solutions.
  • It's crucial to understand solubility and stability for advice on mixing with other liquids.

Oral Rehydration Solutions (ORS)

• Purpose: To replace fluids and electrolytes lost due to diarrhea, preventing dehydration.
• Composition: A typical ORS contains sodium, potassium, chloride, citrate, and dextrose.
• Availability: Available over the counter (OTC) in liquid or powder form for reconstitution.
• Important Considerations:
  • Use the specific amount of water for reconstituting powder forms.
  • Do not mix ORS with other electrolyte-containing drinks.

Oral Colonic Lavage Solution

• Purpose: To prepare the bowel for procedures like colonoscopy, replacing traditional methods.
• Composition: A balanced electrolyte solution with polyethylene glycol (PEG-3350).
• Advantages:
  • Less time and dietary restriction.
  • Eliminates need for cleansing enemas.
• Mechanism of Action:
  • PEG acts as an osmotic agent, drawing water into the bowel.
  • Balanced electrolytes prevent significant changes in water or electrolyte balance.

Solubility

• Weak bases, including alkaloids, local anesthetics, and antihistamines, are soluble in acidic solutions but precipitate when pH increases.
• Weak acids, like barbiturates and sulfonamides, form water-soluble salts in basic solutions and precipitate with lower pH.
• Solubility is determined by preparing a saturated solution at a specific temperature and analyzing the amount of solute dissolved in a solvent.

General Rules of Solubility: Inorganic Molecules

• Monovalent cations and anions usually have good water solubility (e.g., NaCl, KI).
• Compounds with one monovalent ion also tend to be water soluble (e.g., BaCl2, Na2SO4).
• Multivalent cations and anions often have poor water solubility (e.g., CaSO4, BaSO4), with exceptions like ZnSO4 and FeSO4.
• Alkali metal salts are generally water soluble (exception: Li2CO3).
• Ammonium and quaternary ammonium salts are water-soluble.
• Nitrates, nitrites, acetates, chlorates, and lactates are generally water soluble (exceptions: Silver and mercurous acetate).
• Sulfates, sulfites, and thiosulfates are generally water soluble (exceptions: Calcium and barium salts).
• Chlorides, bromides, and iodides are water soluble (exceptions: Salts of silver and mercurous ions).
• Acid salts corresponding to insoluble salts are more water soluble than the original salt.
• Hydroxides and oxides of compounds other than alkali metal cations and the ammonium ion are generally water insoluble.
• Sulfides are water insoluble except for their alkali metal salts.

Filtration

• Darcy's equation describes factors influencing filtration rate: dv/dt = K×A× ΔΡ/ η×1
• Surface area, pressure difference, and viscosity influence filtration rate.
• Filters include woven materials, porous plates, membrane filters, unwoven fibrous materials, and granular or powdered materials.
• Ultrafilters and microsieves separate microorganisms and small particles.

Elixirs

• Clear, sweetened hydroalcoholic solutions intended for oral use.
• Non-medicated elixirs serve as vehicles, while medicated elixirs have therapeutic effects.
• Less sweet and viscous than syrups due to lower sugar content.
• Better than syrups in maintaining both water-soluble and alcohol-soluble components.
• Alcohol content varies based on solubility properties of individual components.
• Commonly sweetened with sucrose or sorbitol and flavored for palatability.
• High alcoholic content elixirs use artificial sweeteners like saccharin.
• Elixirs with over 10% alcohol are usually self-preserving.
• Medicated elixirs are formulated to provide a typical adult dose in a convenient measure (e.g., 5-10mL).
• Provide flexibility for dosage administration to those struggling to swallow solids.
• Disadvantageous due to alcohol content for children and those avoiding alcohol.
• Store in tight, light-resistant containers and avoid excessive heat.

Dry Mixtures for Solution

• Certain antibiotics lack stability in aqueous solution.
• Pharmacists receive dry powder or granules for reconstitution with water before dispensing.
• Contains all formulative components except solvent.
• Reconstituted solution remains stable for a labeled period (usually 7-14 days) in refrigeration.
• Discard any remaining medication after completing the prescribed regimen.

Oral Solutions

• Pharmacists may dispense commercial oral solutions, dilute existing solutions, reconstitute dry mixtures, or compound solutions from bulk components.
• Pharmacists should understand the dispensed product's use, dosage, administration, and storage.

Oral Rehydration Solutions

• Diarrhea can cause rapid fluid loss leading to dehydration.
• Oral rehydration solutions replace lost fecal water and replenish sodium, potassium, and bicarbonate ions.
• Important for managing dehydration and acidosis caused by diarrhea.
• Nutritional foods like bran and soybean formula aid in recovery.

Preparation of Elixirs

• Prepared by simple solution with agitation and/or mixing of liquid ingredients.
• Alcohol-soluble materials are dissolved separately in alcohol, water-soluble components in water.
• Water solution is added to the alcohol solution to maintain alcoholic strength.
• Filtration can be used if the mixture becomes cloudy due to flavoring oil separation.
• Talc acts as a filter aid, absorbing excess oils.

Nonmedicated Elixirs

• Useful for adding therapeutic agents to pleasant-tasting vehicles or diluting existing medicated elixirs.
• Considerations include drug solubility and stability in water and alcohol.
• The diluent's alcoholic concentration should match the elixir being diluted.
• Flavor and color should be compatible with the medicated elixir.
• Commonly used nonmedicated elixirs include Aromatic elixir, Compound benzaldehyde elixir, and Isoalcoholic elixir.

Medicated Elixirs

• Used for their therapeutic benefits.

Antihistamine Elixir

• Used for symptomatic relief of allergic disorders.
• Suppress symptoms caused by histamine.
• Common side effects include sedation, dryness of nose and throat, dizziness, and disturbed concentration.

Barbiturate Sedative and Hypnotic Elixirs

• Barbiturates act as sedatives and hypnotics, depressing the central nervous system.
• Doses determine effect from sedation to hypnosis to respiratory depression.
• Administered in small doses for daytime sedation and larger doses at night for insomnia.

Water for Injection

• It is sterile water for injection, used as solvent, vehicle, or diluent for sterilized injectable medications.
• It is packaged in single-dose containers of up to 1 L

Sterile Water for Injection

• It is a type of water for injection, containing one or more antimicrobials.
• Used as a sterile vehicle to prepare small volumes of injectable solutions.
• Packaged in prefilled syringes or vials containing no more than 30 mL.

Preparation of Solutions

• Most pharmaceutical solutions are unsaturated with solute.
• The amounts of solute are usually well below the capacity of the solvent.
• Percent strength is the standard way to express the strength of pharmaceutical preparations.

Properties of oral solutions

• Palatable: The preparation must be acceptable by the patients in terms of taste, appearance, and odor. This is affected by several factors, such as patient age, dosage form, and the taste and color of the drug.
• Stability: Ensures the patient will receive the stated amount on the label and maintains stability for a specific time (stored at room temperature).

Elixirs

• Clear, sweetened hydroalcoholic solutions intended for oral use. They are usually flavored to enhance palatability.
• Less sweet and viscous than syrups because they contain a lower proportion of sugar.
• Better than aqueous syrups in maintaining both water-soluble and alcohol-soluble components in solution.
• Alcohol content varies widely depending on the solubility characteristics of the elixir components.
• Usually self-preserving due to their high alcohol content (over 10%).
• One or two teaspoonfuls (5 or 10 mL) provide the usual adult dose of the drug.

Magnesium Citrate Oral Solution

• Colorless to slightly yellow, clear effervescent liquid with a sweet, acidulous taste and lemon flavor.
• Contains an amount of magnesium citrate equivalent to 1.55 to 1.9 g of magnesium oxide in each 100 mL.
• Prepared by reacting magnesium carbonate with citric acid, flavoring and sweetening with lemon oil and syrup, filtering with talc, and then carbonating it with potassium or sodium bicarbonate.
• Employed as a saline cathartic.

Sodium Citrate and Citric Acid Oral Solution

• Contains sodium citrate 100 mg and citric acid 67 mg in each milliliter of aqueous solution.
• Administered orally in doses of 10 to 30 mL as frequently as four times daily as a systemic alkalinizer.
• Useful for maintaining an alkaline urine in patients with uric acid and cystine calculi of the urinary tract.
• Also used as an adjuvant in gout therapy.

Preparation of Elixirs

• Usually prepared by simple solution with agitation and/or by admixture of two or more liquid ingredients.
• Alcohol-soluble materials are dissolved separately in alcohol and water-soluble components are dissolved separately in purified water.
• The aqueous solution is added to the alcoholic solution, not the reverse, to maintain the highest possible alcoholic strength.
• Frequently, the final mixture is cloudy, due to separation of some of the flavoring oils by the reduced alcoholic concentration.

This quiz explores various drug administration routes and solubility concepts vital for understanding pharmacology. It covers rate-controlled actions, topical applications, injections, inhalation therapies, and factors influencing solubility. Test your knowledge on how these methods impact drug delivery.