Dosage forms (also called unit doses) are pharmaceutical drug products in the form in which they are marketed for use, with a specific mixture of active ingredients and inactive components (excipients), in a particular configuration (such as a capsule shell, for example), and apportioned into a particular dose. The term unit dose can also sometimes encompass non-reusable packaging as well (especially when each drug product is individually packaged), although the FDA distinguishes that by unit-dose "packaging" or "dispensing".
The USP classification ("Taxonomy") of pharmaceutical dosage forms is presented in an article of the USP Pharmacopeial Forum 39. The USP categorises 5 different dosage forms:
Injections and implanted drug products (parenteral)
Oral drug products
Topical and transdermal drug products
Mucosal drug products (= dosage forms absorbed via the mucous membranes)
Products for inhalation or nasal administration
Depending on the physical properties, dosage forms come in several types:
Solid dosage forms
Semisolid dosage forms
Liquid dosage forms
Gaseous dosage forms
Notably, the route of administration (ROA) for drug delivery is dependent on the dosage form of the substance in question. A liquid dosage form is the liquid form of a dose of a chemical compound used as a drug or medication intended for administration or consumption.
Various dosage forms may exist for a single particular drug since different medical conditions can warrant different routes of administration. For example, persistent nausea, especially with vomiting, may make it difficult to use an oral dosage form, and in such a case, it may be necessary to use an alternative route such as inhalational, buccal, sublingual, nasal, suppository or parenteral instead. Additionally, a specific dosage form may be a requirement for certain kinds of drugs, as there may be issues with various factors like chemical stability or pharmacokinetics. As an example, insulin cannot be given orally because upon being administered in this manner, it is extensively metabolized in the gastrointestinal tract (GIT) before reaching the bloodstream, and is thereby incapable of sufficiently reaching its therapeutic target destinations.
The most common dosage forms are those that are administered orally. Taking an oral medication is the most convenient method to deliver medication, which in turn makes it the most in demand, which leads to mass production lower manufacturing costs. Some medications are not available in oral form because they cannot be properly absorbed in the GI tract. For instance, heparin is only available as an injectable formulation because it is ineffective when administered orally. The route of administration and dosage form are also determined by other factors, including the age of the patient, the disease being treated, the area of the body that the drug needs to reach, the ease of administration, and the characteristics of the drug.
Dosage forms may also contain the following:
Additives—Additives are inert ingredients that may be needed for a successful preparation of the dosage form.
Binders—Binders promote adhesion of active and inactive ingredients in the tablets.
Diluents—Diluents are additives used to increase the bulk weight or volume of a dosage form
Excipients—Excipients are inactive substances used as a carrier for the active ingredient.
Preservatives—Preservatives are substances that prevent or minimize the growth or other microorganisms in the dosage forms, typically used in multi-dose vials. Single-dose vials are discarded immediately after use, while multi-dose vials, once opened, may be stored for a period. After a vial has been opened, however, the risk of bacterial overgrowth increases. To prevent or minimize the risk of bacterial overgrowth, preservatives are added to the medication.
Solid dosage forms include tablets, capsules, caplets, lozenges/troches, pastilles, powders, and granules. Solid dosage forms offer several advantages:
Ease of packaging, storage, and dispensing
Little or no taste or smell
Solid dosage forms may, however, be difficult to swallow, have a slow onset of action, and may be degraded by the acidic contents in the stomach.
Semisolid agents are different in their composition from liquids or solids. They are usually intended for topical application. They may be applied to the skin, placed on mucous membranes, or used in the nasal, rectal, or vaginal cavity. Example include ointments, creams, lotions, gels, pastes, and suppositories.
An emulsion is a type of semi-solid dosage form. It is a mixture of two substances that are unbendable. One substance is dispersed in the other. An oil-in-water (O/W) emulsion contains a small amount of oil dispersed in water. A water-in-oil (W/O) emulsion contains small amount of water dispersed in oil. An emulsion, which has a different composition than the two individual liquids that are mixed together, is dispensed in containers that hold liquids.
An emulsion is a mixture of two liquids that do not blend. An ointment is an example of a water-in-oil (W/O) emulsion. A cream is an example of an oil-in-water (O/W) emulsion.
Liquid dosage forms contain one or more active ingredients in a liquid vehicle as a solution, suspension, or emulsion. The drug may be dissolved in the vehicle or suspended as very fine particles. They can be administered by many routes, but are often less stable than medications in solid dosage forms.
Liquid dosage forms offer several advantages:
They allow for easier dosage adjustments, particularly for pediatric patients.
They are easier to swallow, particularly for pediatric and geriatric patients.
The onset of action is faster than that of solid dosage forms.
They are easier to place down a feeding tube.
Liquid dosage forms offer several disadvantages:
Loss of potency occurs faster than with solid dosage forms.
There is difficulty in masking bitter taste or odor.
There is a need for preservatives because liquid doses provide an excellent medium for the growth of microorganisms.
There is a potential for dosing inaccuracy.
Some patient populations, such as asthmatic patients, need to have their medications delivered to a specific site in the body, such as the bronchial tree. Gases, vapors, aerosols, powders, spray, solutions and suspensions intended to be inhaled via the nose or mouth are known as inhalations, after the term inhalation, or the acts of inhaling or breathing in. The medication particles must be extremely fine to reach this area effectively. Devices that enable the medications to reach the lungs easily include vaporizers, humidifiers, and nebulizers.
An aerosol is a spray that contains very fine liquid or solid drug particles in a gas propellant that is packaged under pressure. An aerosol dosage form consists of medication, the container, and the propellant. Pressurized aerosol containers should be stored away from heat.
The spray consists of a container that has a valve assembly unit that contains various bases, such as alcohol or water, in a pump-type dispenser.
Transdermal Dosage form is designed to hold a specific amount of medication to be released into the skin and absorbed into the bloodstream over time via a patch or disk. The patch consists of a backing, drug reservoir, control membrane, and adhesive layer. The backing is removed and the adhesive layer is applied to the skin. The drug is slowly absorbed across the membranes of the skin.