Frequency of Adverse Drug Reactions

General experience with allergic adverse reactions shows that most adverse reactions start during the first weeks of treatment, and rarely after months or years (Klein et al. 1976). The problem is, however, difficult to study, as most drugs with common allergic reactions, such as anti-infective drugs, are seldom indicated for a duration of more than 4-6 weeks. 

The time of exposure is extremely important for indications of frequencies. With various ampicillin preparations the frequency of a maculopapular rash varied from a few to 10% or more of the treated patients these numbers are only comparable when equal exposure times are used (Fricker 1976 Shapiro et al. 1969). 

Frequencies of characteristic adverse drug reactions are usually compared with numbers of treatment periods rather than numbers of treated patients. In our opinion, a reaction rate of 10 -10 should be considered as high 10 -10 as intermediate lO -lO as low 10 -10 as very low 10 -10 or less as extremely low. 

The baseline risk for the same syndrome, if known, should always be indicated. 

In the case of life-threatening reactions in a disease with an important indication for a particular drug, very low appearance (10 -10 ), such as anaphylactic shock to penicillin, is usually acceptable (Ids0e et al. 1969). However, it is only permissible to take this type of risk after full consideration of an accurate case history, and the clinical and laboratory situation, and if the treatment possibilities are good. 

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Observational studies of adverse drug reactions identified two clinical factors that appeared to predispose to a high frequency of adverse drug reactions. These were the total number of different drugs the patient was taking and the presence of preexisting kidney failure. 

Thomsen HS, Dorph S. High-osmolar and low-osmolar contrast media. An update on frequency of adverse drug reactions. Acta Radiol 1993 34(3) 205-9. 

Withdrawn in 2001, due to increased frequency of adverse drug reactions... 

Table 3. Frequency of adverse drug reactions in atopic patients compared with non-atopic controls...

Klein U, Klein M, Sturm H et al. (1976) The frequency of adverse drug reactions as dependent upon age, sex and duration of hospitalization. Int J Clin Pharmacol 13 187-195 Koch-Weser J (1968) Definition and classification of adverse drug reactions. Drug Inform BuU 2 72-78... 

In this section, a brief summary of the nature, frequency, and consequences of adverse drug reactions (ADRs) in two clinical situations is presented. There are ADRs experienced by healthy volunteers and patients participating in clinical studies with potential new medicines and those experienced by patients who are prescribed licensed medicines. A review of these two situations points to areas of success with the current practices for non-clinical safety pharmacology testing but also identifies some areas where further research might lead to new or better safety pharmacology tests. Prior to reviewing the literature, some... 

Outcomes, or consequences, of the services described were considered in all 104 papers. Nineteen (18%) of the papers were found to be full economic analyses because they considered two or more alternatives to care and measured both input costs and outcomes. The most common outcomes measured were drug costs avoided, length of hospital stay, use of nonpharmaceutical resources, rates of adverse drug reactions, frequency of pharmacist-driven therapeutic interventions, and qualitative changes in prescribing patterns. In 93 (89%) of the papers, beneficial financial impacts of clinical pharmacy services were described. 

Metabolic Enzyme" Genetic Variation (Alleles) Frequency of Genetic Variant [% and (Race )] Functional Consequence [% Frequency (Race ) in Population] Drug Substrate Implicated in Adverse Drug Reactions... 

In a review of reports to the Australian Adverse Drugs Reactions Advisory Committee between 1985 and 2001 there were 48 cases of lactic acidosis with metformin (86). In 35 of the 48 cases known susceptibility factors were identified. The estimated frequency was one case of lactic acidosis in 30 000 patients taking metformin. The authors... 

Although the labels for all antidepressants mention the risk of inducing mania, none of them mention the high frequency of this adverse drug reaction, and none describe its potentially devastating impact on the victim s life. 

Allergic skin reactions occur in 1-2% of patients who take nitrofurantoin and comprise about 21% of all adverse reactions to nitrofurantoin (5,71). They often occur with other reactions, such as drug fever, lung, or hver reactions. The lesions can present as pruritus, as macular, maculopapular, or vesicular rashes, urticaria, angioedema, or erjdhema multiforme (72). The frequency of serious cutaneous reactions (erythema multiforme, Stevens-Johnson syndrome, or toxic epidermal necrolysis) after nitrofurantoin has been estimated to be 7 cases per 100 000 exposed individuals (71). 

If this complication occurs, the drug should be withdrawn immediately (7). A report has given some data on the frequency with which tiaprofenic acid cystitis-related disorders were reported to the UK s Committee on Safety of Medicines. Between 1981 and 1996, 770 adverse drug reactions involving 221 patients were reported. A peak in the reporting of cystitis was noted in 1994, when tiaprofenic acid product information was changed and advice was sent to UK doctors warning about cystitis-related... 

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