Introduction to DoSAge fOrmS

Dosage Forms (Part 2)

Siti Halimah BuxPharmacy Practice Department

Kulliyyah of Pharmacy, IIUM Kuantan.

Dosage Form - Design

Three (3) major considerations: Physical and chemical properties of the drug Biopharmaceutical aspect - route of

administration - rate of absorption - extent of absorption Therapeutic Aspect (performance of the drug) - bioavailability of the drug

1.Physical & Chemical Properties Of The Drug Stability some drugs are not stable in solution form or are inactive when

hydrolysed e.g certain antibiotics Drugs stable in solution – need to consider stability under various pH

conditions, temperature etc. Compatibility whether compatible with other ingredients in the formula. Solubility Most drugs relatively soluble in aqueous soln. for it to be absorbed. Depends on pH Particle size The smaller the size, the larger is the surface area, the better is the

absorption

2. Biopharmaceutical Aspect -Route of Administration

Oral

Parenteral Rectal / Vaginal Respiratoral Topical

Dosage Form Design 1 – Tablets/Capsules Delayed action and enteric coated tablets Designed to delay the release of drug in the stomach

so that: - it would not be destroyed by gastric juices - the stomach lining will be protected by irritating effect of the drug - promote absorption (for drug which is better

absorbed in the intestine)

Sugar-coated (dragee), film-coated and chewable tablets

Designed to: - protect the drug from air and humidity - mask the drug’s unpleasant taste or odour - improve the drug’s appearance Sublingual tablets / capsules

Designed to:- increase absorption bioavailability increase

- prevent drug from being destroyed by gastric juices

Dosage Form Design 2 – Injectables / Parenteral Preparations Major Routes of Parenteral Administration:1. Intradermal Injection – into skin between the

dermis and epidermis, mainly for diagnosis of allergy and immunity e.g. Penicillin test dose

2. Subcutaneous Injection – into tissue immediately under the dermis e.g insulin inj.

3. Intramuscular Injection – into skeletal muscle, usually deltoid muscles in shoulder or gluteal muscles in the buttock

Injectables / Parenteral Preparations1. Intravenous Injection – directly into superficial

vein2. Intra-arterial Injection- directly into an artery,

usually for diagnostic procedure e.g. x-ray contrast3. Intraspinal Injection- into the intrathecal or

intracisternal e.g. spinal anaesthetics4. Intra-articular Injection- directly into synovial

fluid of a joint

Dosage Form Design 3 – Suppositories & Pessaries Route of Administration : Rectal or Vaginal,

occasionally urethera Used when normal routes are not suitable (when

drug is destroyed in the GIT, irritant to the stomach) or inaccessible (when patient is unconscious or vomitting)

To produce a local action e.g. haemorrhoid preparations; laxative preparations

To produce a systemic effect e.g. paracetamol suppositories for fever

Dosage Form Design 4 – Respiratoral Preparations (Inhalers) Three types of inhalers available in Malaysia:

* Pressurised aerosol inhalers ( metered dose inhaler) – small, portable devices that deliver medication in an aerosol form so it can be inhaled* Dry powder inhalers – dry micronised powders inhaled directly into the lung* Nebulizers - Respirator solutions are placed in a chamber and the nebulizer produces a mist. This mist is delivered to the patient via a mouth-piece or face mask.

Dosage Form Design 5 – Topical Preparations Creams – semi-solid preparation used either for

therapeutic or prophylactic purposes; due to their high water content it provides a moisturising effect on dry skin.

Ointments – greasy, semi-solid; act as protective agent and has emollient ( soothing) effect

Lotions – used for its cooling and soothing effect Transdermal patches e.g. nicotine and

nitroglycerine patches. When supplements/drugs are delivered transdermally they go directly to the blood stream initially bypassing the liver (95% get to the cells where needed)

Implants – may be inserted into various parts of the body :* to replace a diseased structure* to improve appearance* to maintain proper functioning of an internal

organ* to treat certain disorders* to deliver drugs or hormones

Other Dosage Form Designs Radiopharmaceuticals A radiopharmaceutical is a radioactive agent i.e. it

incorporates a radioactive isotope. They are used for:a) Diagnostic purposes whereby the radioactive agent is taken up by an organ of the body. The radioactivity is detected and pictures are produced by special imaging equipment.

b) Treatment of certain diseases e.g. cancer whereby the radioactive agent is taken up in the cancerous area and destroys the affected tissue

Enemas – are aqueous oily solutions that are introduced into the rectum for:* cleansing e.g. removing faeces in constipation* therapeutic effect e.g. it may contain an anti-inflammatory drug which exerts a local effect in the large bowel* diagnostic purposes e.g. x-ray contrast media administered as an enema to aid diagnostic investigation of the large bowels

3. Therapeutic Aspect Nature of the disease - what is the most suitable dosage form - which is the best route for administration - what is the desired duration of action - dose frequency

Age of the Patient – child or adult

WORDS OF WISDOMREMEMBER THE 3 Rs