PTCB Guide to Solid Dosage Forms.

Solid Dosage Forms as a Topic of the PTCB Exam.

For the PTCB exam, pharmacy technicians are required to have extensive knowledge of dosage forms – the means through which active ingredients are delivered to patients. Today, we review the key solid dosage forms – their advantages and disadvantages, as well as essential clinical considerations.

Medicines are delivered to the body in different ways. For instance, some medicines are solids, such as tablets and capsules whereas other dosage forms are liquids, such as solutions and suspensions. More specifically, dosage forms have two essential elements:

• The drug
• The delivery system

In other words, it matters how any drug is delivered to the body. When we consider tablets, for example, they are not just the “drug”. There are other ingredients – called excipients – in the medicine that help it work. Therefore, medicines are composed of the following two elements:

• Active ingredient: the part of the medicine designed to treat the patient, also referred to as the ‘drug’.
• Excipients: inactive ingredients added to the medicine. Excipients include preservatives, coloring agents, and stabilizers.

In other words, a drug and a medicine are not the same thing. The drug is the active ingredient, whereas the medicine is total between ‘drug + excipients’.

Solid Dosage Forms.

Key examples of solid dosage forms include:

• Tablets
• Capsules
• Lozenge
• Powders
• Granules

Of course, not many medicines today are composed of powders and granules, though some are. Take inhaled medicines, for example. Beta-2 agonists, such as albuterol, need to be inhaled so that very fine drug particulates reach the bronchi of the lung.

Lozenges are hard medicines that dissolve slowly within the oral cavity. They are designed to prolong the effect of the medicine within its target site. For this reason, lozenges are used for their antiseptic, antitussive (cough suppressing), and mild anesthetic effects.

Below, we take a closer examination of tablets, capsules, and suppositories.

Tablets.

Many drugs today are available as tablets. Tablets are one of the most common solid dosage forms and come with many different advantages, including:

• Tablets are simple and convenient to use
• Quickly and safely manufactured into convenient doses
• Tablets are carried within portable packages, improving compliance
• Tablets can be made to disguise unpleasanttastes from drug or excipients
• Tablets can be easily identified by healthcare professionals – markings etc.
• Tablets can be taken by patients themselves for added convenience

That said, there are numerous drawbacks of tablets. These include:

• Not all drugs are suitable for oral use. Many drugs are degraded by stomach acid, such as insulin. However, some tablets are available as enteric-coated preparations to limit the damage of the low pH gastric environment.
• Some drugs are deactivated by the liver, as the drug passes from the GI tract via the portal vein into the liver. This metabolism risk of the liver is referred to as the “first pass effect”.
• Tablets may not be suitable when immediate therapy is required. After all, it takes time for tablets to be degraded by the GI tract, absorbed into the bloodstream, and delivered to the site of intended action.
• Following on from the above, tablets are also not suitable in patients who are unable to swallow, either from disease or from loss of consciousness.
• Some drugs are poorly absorbed by the GI tract. As a result, high doses need to be taken to ensure a therapeutic dose is reached. Higher doses can lead to greater and more unpleasant side effects.

Tablets are available in a wide variety of forms:

• Chewable – nicely flavored, useful for children
• Enteric-coated – coated to prevent acid destruction in the stomach
• Sublingual – to be taken under the tongue
• Buccal – to be taken inside the cheek
• Film-coated – added protection, either from the sun, or to mask taste
• Effervescent – granules dissolved in liquid to release carbon dioxide
• Pellets – implanted beneath skin to prolong continuous drug absorption
• Vaginal – inserted into the vagina to directly release drug to site of action

Tablets remain, then, the most popular dosage form prescribed by pharmacies.

Capsules.

Capsules are one of the most popular dosage forms. There are two primary types:

• Hard-shelled capsules. These capsules contain powder or power-like content. A smaller diameter half is filled and secured into a larger diameter half of the capsule.
• Soft-shelled capsules. These are typically filled with oils or active ingredients that have been suspended or dissolved in oils.

Markings found on the capsule help to identify its size:

Size 000 is generally too large to be taken by patients. Some capsule formulations are made so that the contents may be sprinkled on food.

Capsules have many of the same advantages of tablets:

• Convenient to take, portable etc.
• Easy to swallow
• Due to the outer shell, capsules do not have an unpleasant taste
• Easy to produce on mass scale

Let’s now turn our attention to suppositories.

Suppositories.

Suppositories are one of those solid dosage forms applied to the rectum, vagina, or urethral tract. When inserted vaginally, and if intentionally shaped for vaginal use, they may also be known as inserts.

Suppositories are composed of an active ingredient within what’s called a suppository base. Examples of bases include:

• Polyethylene glycol
• Cocoa butter
• Hydrogels
• Glycerinated gelatin

This base, once it enters the body, dissolves in the heat and released the drug either locally or into the bloodstream for systemic effects. Suppositories should always be unwrapped before insertion. Pharmacy technicians should instruct their patients on how to correctly use suppositories.

Conclusion

During the PTCB exam, candidates are expected to have a thorough knowledge of dosage forms. Here, we’ve talked about solid dosage forms, but there are many other types of dosage form we have yet to examine. These include liquid dosage forms, semisolid dosage forms, and injectable dosage forms.

When studying dosage forms, you need to bear the following 4 considerations in mind:

• The advantages and disadvantages of each dosage form
• Why one dosage form is preferred over another
• How to counsel patients taking these types of dosage form
• How each dosage form is manufactured

Hope you found this review helpful. Check back to our blog for even more exclusive content to help you study and pass your pharmacy technician exam.