Solutions Dosage Form

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What are solutions?

Solutions are liquid preparations that contain one or more chemical substance dissolved in a suitable solvent or mixture of mutually miscible solvents.

________ are liquid preparations that contain one or more chemical substance dissolved in a suitable solvent or mixture of mutually miscible solvents.

Solutions

What is the solute in solutions? solvent?

The solute in solutions may be liquid, solid, or less frequently used gas; however, the solvent is always a liquid.

What are the advantages of solution as a dosage form?

Self administration
Easy to swallow (oral)
Patient compliance (due to flavor and was ease of swallowing)
Uniformity of dose
Flexible dosing
Prompt Action

Solution has a ______ surface area.

LARGE
It also doesn't have to be dissolved, which may allow the drug to be directly absorbed.

Which gets into the bloodstream faster: solutions or tablets/capsules?

Solutions get into the bloodstream faster; capsules and tablets have to be dissolved before they may be absorbed.

_______ is used to help with patient compliance with solutions.

Flavoring may be used to help with compliance.

What are disadvantages of solution as a dosage form?

Dosing Accuracy
Microorganisms and contamination
Handling, packaging, shipping
Heavy liquids, large volumes and breakable containers.

What is a large disadvantage of solution as a dosage form?

A large disadvantage of solutions is dosing accuracy, due to different size spoons or improper reading of cups.

Why is contamination a problem in solutions?

In solutions dispensed as a multi-dose containers, there is always an increased risk of microorganisms.

A one teaspoon dose contains a _____ number of active substance particles (medication).

FINITE

Why did the FDA pull a lot of pediatric solutions from the market?

FDA pulled many pediatric preps from the market due to improper dosing by the general public.

How are solutions classified?

Solutions may be classified by:
The Basis of Their Use
The Basis of Their Composition

Solutions may skip the first step of absorption: dissolving.

...

What are the classification of solutions based on their use?

Solutions Classified on the Basis of their Use:
Oral
Otic (ear drops)
Opthalmic (eye drops and washes)
Topical/Dermal (lotions)
Parenteral
Nasal (drops, aerosols, washes)
Rectal (enemas)
Urethral or vaginal (douches)

_____ solutions include syrups, elixirs, aromatic waters, mouth washes and gargles

Oral solutions

Note: Oral solutions contain both mouth washes and gargles, which cause local effect and are not swallowed.

Note: Syrups, spirits, tinctures, oral solutions, elixirs and aromatic waters are meant to give a systemic type of response. Administered in solution form means they are soluble in aqueous solutions and their absorption from the GI tact into systemic circulation may occur rapidly than suspension or solid dosage form.

Injections

Certain solutions are prepared to be sterile and pyrogen free and intended for parenteral administration

How may solutions be classified by their composition?

Solutions classified by their composition:
Syrups
Elixirs
Spirits
Aromatic waters
Tinctures/fluid extracts

Describe the formation of a solution (in basic terms).

Formation of a solution involves:
Solutes (drugs, color, flavoring, sweeteners)
+
Liquid solvent (water, oil, alcohol, propylene glycol)
=
Solution

What are types of solvents used in solutions?

Water, oil, alcohol and propylene glycol are all types of solvents used for solutions.

Aqueous solutions containing a sugar

syrups

sweetened hydroalcoholic solutions

elixirs

alcoholic solutions of aromatic materials

spirits

aqueous solutions of aromatic materials

aromatic waters

solutions prepared by extracting active constituents from crude drugs

tinctures or fluid extracts

What solvent must be used for solutions?

Suitable solvent or mixture of mutually miscible solvents (to dissolve the solute).

When making solutions, what must the pharmacist be aware of?

For single solute or multiple solute solutions, the pharmacist must be aware of the solubility characteristics of the solutes and the features of the common solvents. USE USP-NF

What are intramolecular forces?

Intramolecular forces are attractive forces between atoms that lead to the formation of molecules and ions.

What are intramolecular forces responsible or attributed to?

Intramolecular forces (developed between like molecules) are responsible for the physical state (solid, liquid or gas) of the substance under certain temp and pressure.

Under ordinary conditions, most organic compounds and drug substances form molecular ______.

solids

What is occurring when molecules interact?

When molecules interact, attractive and repulsive forces are in effect. Attractive forces cause the molecule to cohere and repulsive forces prevents bonding. When the forces are equal, PE is minimal and system is stable

How do dipolar molecules arrange themselves?

Dipolar molecules tend to align themselves with other dipolar molecules so the negative pole of one molecule points toward the positive pole of the other.

When a solute dissolves in a substance, what must occur?

When a solute dissolves, the substance's intermolecular forces of attraction must be overcome by forces of attraction between solute and solvent.

A solute dissolves in Solvent:

Break solute-solute forces
Break solvent-solvent forces
Form solute-solvent forces

______ ________ keep solute together with the solvent.

Intermolecular forces

What does the solubility of a solute in a solvent indicate?

The solubility of a solute in a solvent indicates the MAXIMUM CONCENTRATION to which a solution may be prepared, with the agent and solvent.

What does saturated indicate?

When a solvent has dissolved all the solute possible at a given temp., the solvent is saturated.

What is supersaturated?

If the temperature of the solution is increased and more solute is able to be added to the saturated solvent, then called supersaturation.

The maximum possible concentration of a solution varies greatly and depends in part on the chemical constitution of the solute.

...

How can one dissolve more solute than normally allowed?

To Dissolve More Solute than Normal:

Alteration of the pH of solution
Substitution of solvent
Selecting a different solubilizing agent
Selecting a different chemical salt form of
the medicinal agent

What factors affect solubility of a solute in solvent?

Physical and chemical properties of solute and solvent, temp. of solution, pressure, pH of solution, state of subdivision of solute and physical agitation applied to solution when it dissolves.

How does temperature affect the solubility?

Chemicals absorb heat when they are dissolved, resulting in a increased solubility in increasing temp.

However, some chemicals have negative heat of solution, resulting in a decreased solubility in increasing temp.

Is the solubility of a pure chemical substance a constant?

The solubility of a pure chemical substance is a constant under temp. and pressure.

BUT its rate of solubility in a solution depends on particle size and extent of agitation.

The number of drug molecules in solution is what is important, because every drug molecule in solution has the ability to act on a receptor at the site of action.

Fewer molecules of drug in solutions means a greater volume is required of the solution/dose.

Rate of solution

The speed at which the solute dissolves in a solvent.

Agitation

physical agitation may affect the solubility; shake well before use because of the properties of the solution.

What are the 4 factors that affect solubility?

Solubility is affected by 4 factors:
Physicochemical Properties of Drug
Solvent
Pressure
Temperature
Physicochemical Properties of Solvent

In relation to solubility, the finer the powder _________________________.

The finer the powder, the greater the surface area->which comes in contact with the solvent. Thus, the more rapid the dissolving will occur.

Why is agitation important?

Physical agitation (shaking) may affect solubility, because the greater the agitation the more unsaturated solvent passes over the drug and the faster the formation of the solution.

The greater the agitation=the faster the formation of solution

The finer the powder=the more rapid dissolving=the faster the formation of solution

Many organic medicinal agents are ______ acids and _____ bases.

Organic medicinal agents are WEAK acids and WEAK bases.

What does the solubility of many organic medicinal agents depend on? Why?

The solubility of many organic medicinal agents depends on the pH of solvent.

Organic medicinal agents are weak acids and weak bases, what do they react with?

The weak acid and weak base drugs interact either with strong acids or strong bases to form water-soluble salts.

Drugs interact with _____ acids or _____ bases to from _______-_______ _____.

Drugs interact with STRONG acids or STRONG bases to form WATER-SOLUBLE SALTS.

The solubility of a drug in a solvent depends largely on the ______ of the solvent.

pH

What are examples of weak base drugs?

Alkaloids (codeine)
Antihistamine (diphenydramine)
Local anesthetics (procaine)

A weak base drug will be soluble in a _______ solution of _______

Soluble in a DILUTE solution of ACID

Alkaloids

Weak base

Codeine

weak base drug

morphine

weak base drug

antihistamine

weak base drug

diphenhydramine

weak base drug

promethazine

weak base drug

local anesthetics

weak base drug

cocaine

weak base drug

procaine

weak base drug

tetracaine

weak base drug

Weak bases _____ very soluble in water, but _____ soluble in dilute solutions of acid.

Weak bases AREN'T very soluble in water, but ARE soluble in dilute solutions of acid.

A weak base drug and a solution of dilute acid will form a water-soluble salt. What is the importance?

Pharmacist have prepared many acid salts of these organic bases to enable the preparation of the aqueous solutions.

What happens if the pH of the aqueous solution changes that has the organic bases?

If the pH of the aqueous solution of the salts is changes by the addition of the alkali; then the free base may separate from solution. UNLESS it has adequate solubility in water.

Weak acid drugs will form water-soluble salts in ________ solutions.

Weak acids form water-soluble salts in basic solutions. (IF pH is lowered, the weak acid may separate from solution. UNLESS it has adequate solubility in water).

barbiturate drugs

weak acid drug

phenobarbital

weak acid drug

sulfonamides

weak acid drug

sulfadiazine

weak acid drug

sulfacetamide

weak acid drug

How is the solubility of a substance in a given solvent determined?

The solubility of a substance in a given solvent is determined by preparing a saturated solution of it at specific temp and determining the amount of chemical dissolved in a given weight of solution.

When the exact solubility has not been determined, the general expressions of relative solubility may be used. What are expressions of solubility?

Very soluble
Freely soluble
Soluble
Sparingly soluble
Slightly soluble
Very Slightly soluble
Practically insoluble or insoluble

Very soluble

1 part solvent required for 1 part of solute

Practically Insoluble

10,000 part solvent required for 1 part of solute.

As the solubility decreases, it indicates more and more solvent is needed to dissolve the same amount of solute.

A lot more liquid is needed to dissolve the same number of drug molecules.

If you had a slightly soluble drug and a soluble drug, which would have a greater number of drug molecules in a given amount of solvent?

The soluble drug would have a greater number of drug molecules in a given amount of solvent.

Why are weak acids and weak base drugs combined with dilute base and acids?

They form acidic or basic salts, which are more soluble in water than the weak acid or weak base by itself.

Weak base drugs are more soluble in ______ ______ (like alcohol), than are the corresponding salt form.

ORGANIC SOLVENTS

Like Dissolves Like

A solvent having a chemical structure most similar to that of the intended solute will be most likely to dissolve it.

Organic compounds are more soluble in _____ ____ than in water.

Organic compounds are more soluble in organic solvents than in water.

The ability of a solvent to dissolve a solute depends on....

its effectiveness in overcoming the electronic forces that hold the atoms of the solute together and the corresponding lack of resolute on the park of the atoms themselves to resist the solvent action.

During dissolution, the molecules of the solvent and the solute become uniformingly mixed and the cohesive forces of the atoms are replaced by new forces as a result of the attraction of the solute and solvent molecules for one another.

...

Acidic salts of these organic bases enable preparation of aqueous solutions.

Basic salts of these organic acids enable preparation of aqueous solutions.

Atropine

weak base drug

codeine

weak base drug

morphine

weak base drug

phenobarbital

weak acid drug

sulfadiazine

weak acid drug

How much water is required to dissolve 1 gm of atropine? atropine sulfate?

Atropine (1 g) require 455 ml of water,
atropine sulfate (1 g) requires 0.5 mL of water. This difference is because if you make water-soluble salt already and dissolve in water, it won't require very much drug. However, if you start with the medicinal organic drug need a lot more water because lipophilic.

What is codeine soluble in?

Codeine is a weak base, so it will be soluble in a weak acid that will make it a water-soluble salt.

Water Content of Drug vs. Their Salt

The water content required to dissolve 1 g of the drug (weak acid or base) is LARGE, while the water content required to dissolve 1 g of their salt is LOW.

________ is always the go between for lipophilic and hydrophilic compounds.

Alcohol

The amount of alcohol needed to dissolve a solute indicates ________________________________.

Indicates the chemical characteristic of the drug (solute).

The more alcohol required to dissolve a solute _________________________.

The more lipophilic=hydrophobic (organic) a drug (solute) is.

Huge molecules that are organic means they have _______ properties, which means they are ______.

Organic molecules have HYDROPHOBIC properties, which means they are HYDROPHILIC.

What are the most common solvents?

The most common solvents are:
Water
Alcohol
Glycols
Syrups

Tricky: Syrups are a multicomponent solvent already that are allowed to dissolve certain types of drugs...ask?

...

What is the best all around solvent?

Water is the best all around solvent.

What is tap water?

Tap water is purified water than contains less than 0.1% of total solids.

Is water a good solvent?

Naturally occurring water exerts its solvent effect on most substances it contacts and thus is impure. It contains varying amounts of sodium, potassium, calcium, magnesium, iron, chlorides, sulfates, bicarbonates, dissolved and undissolved organic matter and microorganisms.

What is the problem with tap water?

The ions in the water may affect drugs, surfactants, ect. For example, milk has Calcium which may bind to the drug and not be absorbed or metabolized as a result, exiting in the feces.

Tap water may cause the ions to form insoluble complexes with the solute. The insoluble complexes will precipitate out of solution.

In therapeutics, this means they many not be able to achieve pharm. design and are non-absorbable.

Is tap water acceptable to manufacture most aqueous pharmaceutical preparations?

Tap water is NOT acceptable in manufacturing most aqueous pharmaceutical preparations, because of possible chemical incompatibilities between dissolved solids and medicinal agents.

When is tap water acceptable in manufacturing?

Tap water is acceptable in manufacturing for washing the crude vegetable drugs for extract, and when difference between tap water and purified water is of no consequence. Also may be used to clean machine; as long as purified water used to do a final rinse.

USP

Purified Water

What are the various methods to obtain purified water, USP?

Purified water may be obtained by distillation, ion exchange treatment or reverse osmosis.

USP

Purified water that can't have more than 0.001% solids (opposed to 0.1% in tap water).

What is purified water used for?

Purified water is intended for use in preparation of aqueous dosage forms EXCEPT those for parenteral administration (injections)

What are the main methods used in preparation of purified water (USP)?

Main methods used for preparation of purified water are distillation, ion exchange and reverse osmosis.

What is distillation?

Distillation allows ions to concentrate and not reform. It is made from tap water.

What is the disadvantage of distillation?

Distillation increases cost due to heat and maintenance. Must discard first portion of distillate (10-20%) and last portion (10%)

What is ion exchange?

Ion exchange is a method used to purify tap water.

Process of Ion Exchange

Pass water through a column of cation and anion exchangers consisting of water-insoluble synthetic polymerized resins. It removes cations or anions from tap.

What is the advantage of ion exchange over distillation?

Ion exchange has a lower cost because the heat requirement is eliminated (as in distillation) and equipment not as complex as distillation apparatus. Ion exchange has simpler equipment, ease of operation and minimal maintenance.

Ion exchange

Pass water through a column of cation and anion exchange resins to produce USP (purified water).

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