|Essential Drugs -Practical Guidelines (MSF, 1993, 286 p.)|
Stability - Storage
To guarantee effective treatment, it is vital to maintain the quality of the drugs, which means that their identity, dosage and condition have to be assured.
Storage conditions and climatic conditions such as temperature, humidity and light are often very different in tropical countries than in those countries in which the drug was tested. This raises the question whether the drug is still reliable and effective upon arrival.
First, we ought to bear in mind that drugs do not lose their efficacy suddenly at the expiry date. The deterioration process is very slow and varies widely.
There are not only many different products but any given product may also come in various forms and the process of deterioration may vary accordingly.
The determination of the conventional expiry date is based upon the average rate of deterioration that is supposed to occur under normal conditions of light, temperature and humidity. When the expiry date has been calculated on the basis of such conditions, drugs will keep their original therapeutic effect up to the very date of expiry (at least 90% of the active ingredients should be still present and there should not be any substantial increase in toxicity).
In order to obtain good quality drugs, we should try to acquire them in the best possible manner, which means dealing with reliable suppliers and being able to assure quality maintenance through optimum transport and storage conditions.
The quality of generic drugs is equal to that of specialized pharmaceutical products, provided that they are manufactured and controlled properly. When no laboratory is available to test the quality of these generics, we have to rely on the manufacturers and wholesalers for proof of that quality. The choice of a supplier should never depend exclusively upon price.
All drugs should be easily identifiable, both by the medical staff and the patient. In whatever form the drug is packed (bottle, bag or box), it must bear not only the name of the product inside, but also its dose and expiry date. This is particularly important for generic drugs which are sometimes hard to recognize. Different products often look alike or, on the other hand, the same product may exist in different colours and/or forms (e.g. tablets or capsules).
Environmental conditions, such as temperature, air and light, are all factors that influence the storage of drugs.
Standard storage conditions are normally defined as the following temperatures:
-15 to 0°C
0 to + 6°C
+6 to +15°C
+ 15 to + 30°C
However, temperatures during transit and transport may reach 56;C to 60°C in vehicles, wagons or on loading platforms. This means that very often the original expiry dates cannot be guaranteed.
Freezing can be particularly damaging to solutions, causing precipitation of the active ingredients or breaking the ampoules.
Drugs may also be damaged by the influence of humidity and oxygen. Therefore all drug containers must remain closed. Special medical packing, often opaque and waterproof, offers protection against the influences of air and light. Avoid repackaging, until first distribution.
Excessive light may also harm drugs. Solutions are particularly sensitive to light. Injectable preparations have to be kept in the dark in their original packing. Certain types of coloured glass give the misleading impression that they protect drugs from light.
Laboratory equipment, such as chemical substances or rubber and sometimes plastic materials, require protective measures that are comparable to those for drugs.
In most countries, manufacturers art bound by law to have the stability of their products tested under standard conditions. They have to be able to ensure a minimum period of preservation. This is usually between 3 and 5 years, although certain sophisticated products have only a 1 to 2 year period before they expire.
Packaging should bear the expiry date and any specifications as to storage conditions.
When there is no such expiry date, the manufacturing date can be used as a basis for calculating the expiry period. Common antibiotics, hormone preparations, vitamins and liquid drugs in general will last 3 years from the date of manufacture. Other preparations usually have a 5-year period before expiry. This is only a very general rule and there are many exceptions. For instance, it does not apply to products that have to be stored under special conditions (refrigerated.).
Disposable material in sterilized packs may be used as long as the packaging remains intact.
Being well acquainted with the normal characteristics of every drug (colour, smell, solubility, appearance) is essential. It will enable you to detect any changes as soon as they occur. Certain processes may however occur without any detectable change in the appearance of the products.
Active agents that lose their power may have consequences varying in severity both for the individual patient or for a larger group of users.
Antibiotics that have expired, and become less active, may encourage resistant strains.
Any loss in effectiveness should not be compensated for by administering higher doses, since this may lead to serious risks of overdosage of toxic drugs.
Some drugs may even undergo changes that bring about the formation of substances which are far more dangerous and lead to an increase in toxicity. A classic example is tetracycline: when this pale-yellow powder has become brownish and viscous, it must not be used; tetracycline would then be dangerous to use, even if the expiry date has not yet been reached.
Other drugs which lose their effectiveness may produce an increase of allergic reactions. This is the case with penicillin and cephalosporin.
Do not use suppository, ovules, creams or ointments that have melted because of the heat. The active substance will no longer be homogeneously mixed.
Oral rehydration salts can be used as long as they maintain their typical white powdery aspect. Humidity will turn them into a compact mass, more or less brownish and insoluble. Whatever their expiry date, they are then no longer fit for consumption.
DRUGS THAT HAVE EXPIRED
When the only drug available has passed its expiry date, the doctor may in certain cases decide to use it anyway.
It is better to use such drug than to leave a seriously ill patient without treatment. Although a particular drug will not suddenly become unfit for consumption from one day to the next, the following factors should be considered before using any drug after its expiry date. Storage conditions should have been consistently acceptable, i.e. packaging undamaged, stored at an average temperature and protected against humidity and light. It should also be remembered that its physical appearance may not reveal some problems such as insolubility.
The drug sheets give information on the stability of a individual drugs. Unfortunately, research does not yet offer enough readily available information.
Expiry dates on drugs that require a precise dosage need to be strictly respected because of the risk of under-dosage. This is especially the case for cardiotonic drugs or anti-epileptics, and for drugs that may become toxic such as tetracyclines.
THROWING AWAY EXPIRED OR USELESS DRUGS AND MATERIALS
Do not throw away or bury any expired products without taking special precautions. It is advisable to incinerate them. If any tablets, capsules or liquid drugs are enclosed in incombustible packing, that packing should first be removed before incinerating the drugs. Keep a special spot for this operation and bury residual material at a great depth, far away from any well or water reservoir.