Today on ePharmacology we will discuss about the different dosage forms of drugs. Let's start!
A patient suddenly develops upper abdominal pain and attends a private clinic in order to relieve pain. The doctor of that clinic advises the patient to chew an antacid tablet (aluminum hydroxide 325 mg). But the pharmacist gives him a tablet, which is 1,200 mg in weight.
Do you think is there any communication gap between the doctor and the pharmacist? Certainly not!
That tablet actually contains 325 mg of aluminum hydroxide as an active ingredient. To prepare that tablet some other pharmacologically inert substances are added which are called excipients. These are mannitol, sodium saccharin, starch paste, peppermint oil, magnesium stearate, corn starch, methylcellulose, and orange. Here, aluminum hydroxide is a drug. The active ingredient sometimes represents only a small amount of the total weight of a tablet (e.g. digoxin) or capsule. A drug for injection requires a fluid vehicle of varying complexity. The purpose of using these excipients are to- solubilize, suspend, thicken, dilute, emulsify, stabilize, preserve, color, or flavor the drug
All drugs are not used in same amount. They vary in amount. Most of them are prescribed in milligram quantities. For example, paracetamol is administered in 500 mg whereas ethinyl estradiol is administered in 0.05 mg. That is, the former drug is 10,000 times greater than the latter drug. It is a difficult task to ensure the supply of 500mg of paracetamol accurately to the patient without dosage formulation. If 505 mg of paracetamol is administered instead of 500 mg, it will not create any problem. But severe adverse effects develop after administering 5.05 mg of ethinyI estradiol instead of 0.05 mg. Thus, how can you ensure the availability of accurate small amount of ethinyl estradiol? Dosage formulation has solved this problem.
There are four varieties of dosage formulations- solid, semi-solid, liquid and gaseous. In addition, liposome-based formulations are promising and will be the future drug delivery system of a lot of drugs
Organizational structure of this hub:
What we will learn today:
(Click on the links to take you to specific sections of the page)
a. Composition of tablet
b. Types of tablet
a. Composition of capsule
b. Types of capsule
iii. Volatile liquids
Why so many dosage forms?
It is quite natural to raise the question - why do we use so many dosage forms?
The answer is simple.
A single formulation does not allow us to administer a drug via different routes.
For example, a drug in tablet form is suitable for oral (swallow) administration. But it can not be administered by parenteral route until it is diluted in a sterile solvent. Even you can not administer a tablet into the rectum. Thus, suppository- especially designed formulation- is prepared for administration into this route (rectal).
The physiochemical properties of a drug can easily be altered by different dosage forms. It conceals the bitter, salty, or offensive taste or odor of the drug. The damage of drug from moisture can also be prevented. It protects the drug from the destructive influence of gastric acid after oral administration. The adverse effects are also reduced.
Different dosage forms provide the time controlled drug effects and increase the acceptability of drug. For example, metronidazole has a bitter taste which can be masked by making the metronidazole tablet film-coated. Film-coated tablets also prevent the damage of a drug from moisture. Benzylpenicillin is not administered orally, as it will be destroyed within the stomach by gastric juice. So, it is always administered parenterally. In case of enteric-coated tablet, the active ingredient will not be released within the stomach when swallowed. So, the drug that damages the gastric mucosa will not be able to get the chance to produce any adverse effect on the stomach. Everybody does not like to swallow the drugs in tablet form? Liquid dosage form of a drug is more acceptable to the children as well as the elder patients.
Solid dosage form
Solid dosage forms include:
Among them tablet and capsule are mainly used and are administered orally. Powder is the oldest dosage form which nowadays has been replaced by tablet and capsule.
Tablet is a solid dosage form in which powder, crystalline, or granular form of drug is compressed in a disk or molded. It is the most frequently used means of administering a drug. Most of the tablets are administered orally. However, tablets for application as solution, vaginal use (e.g. clotrimazole, sulfathiazole), or external use (e.g. potassium permanganate) are also available.