James W. Black (Nobel Prize in Medicine 1988) indicated: “drugs are useful poisons. Drugs can cure or cause harm. It all depends on the dose administered”.
Pharmacovigilance is defined as a public health activity that analyzes and manages risks of marketed drugs.
The first serious warning appeared in the USA back in 1937 when an elixir caused the death of 107 people, mostly children. This was caused by an excipient used in its preparation. In Europe, a second serious situation occurs: an outbreak of a congenital malformation caused by thalidomide. The first case was pronounced in 1958. In November 1961, thalidomide was initially retired in Germany and later in other countries. Consequences are not known exactly but it is estimated that more than 10,000 children worldwide were born malformed and half of them died due to deformities incompatible with life.
Pharmacovigilance plays an important role establishing relations between treatment and adverse reactions. An example is the association between ACE inhibitors and nonproductive cough.
About 20-30% of liver injuries are due to drugs. Several serious skin reactions (multiform erythema, Stevens-Johnson syndrome and toxic epidermal necrolysis) are caused by drugs (Chan et al., 1990).
The metabolic pathway of cytochrome 3A4 is used by 50% of marketed drugs. Considering their inducers and enzyme inhibitors is the key to prevent pharmacokinetics interactions. Some food can also modify this metabolic path. Grapefruit juice is one of the main examples.
Adverse reactions have become a new public health problem.
When a product is authorized for marketing NOT all about its effects is known. Clinical trials have their limitations. They provide an accurate insight regarding efficacy but it is not complete regarding security. Clinical trials normally test in between 2000 to 3000 humans trying to demonstrate its effectiveness short- and medium-term (<= 1 year). We need at least 30,000 people using a drug to be able to detect an adverse reaction with a 95% statistical probability in a frequency of 1 case per 10,000 people treated.
Every action improving pharmaceutical care has a positive impact on the effective use of medicines:
- Untreated Indications: Detection of new cases of hypertension or diabetes, as part of a pharmaceutical care service, may result in the prevention of cardiovascular complications.
- Selection of inappropriate drugs: Detection of contraindications that cause kidney or liver failure can prevent the manifestation of adverse effects with high economic consequences.
- Using sub-therapeutic dose: Prevention, especially in the case of pain, improves the quality of life of patients.
- Overuse: Providing pharmaceutical care to avoid abuse of beta-2-agonist inhalers by asthmatics.
- Adverse reactions: Prevention on the effect of photosensitivity by recommending use of UV protectants.
- Drug Interactions: Pharmaceutical care is characterized by a broad view of everything that a patient consumes. Detecting interactions avoid therapeutic failures.
Amongst some of the roles of a pharmacist in pharmaceutical care I would like to emphasize this responsibility: “collaboration in pharmacotherapeutic processes and public health surveillance.”
The use of drugs always involves risks, but the greatest risk is to use them without knowledge of its possible risks. It is well known that humans accept higher levels of threat when there is a voluntary choice. Sharing information and involving citizens in the process of evaluation and decision-making get precisely this: transforming an involuntary risk, very badly accepted, on an assumed one.