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Biomedical subjects

Sandra R Knowles

Publications and source records attributed to Sandra R Knowles.

11 recordsLinked to original sources
PubMed2003

Common adverse events associated with the use of ribavirin for severe acute respiratory syndrome in Canada.

Although information on efficacy and adverse drug reactions is lacking, ribavirin has been used empirically for the treatment of severe acute respiratory syndrome (SARS). We report common adverse events in 110 patients with suspected or probable SARS who were treated with ribavirin. Sixty-one percent of the patients had evidence of hemolytic anemia, and hypocalcemia and hypomagnesmia were reported in 58% and 46% of patients, respectively.

Adolescent↗
PubMed2003

Reactive metabolites and adverse drug reactions: clinical considerations.

Idiosyncratic reactions can affect many different organ systems, either as -an isolated event (e.g., hepatitis) or as part of a syndrome (e.g., drug hypersensitivity syndrome). Formation of reactive metabolites of drugs in conjunction with a decreased ability for detoxification is believed to be the initiating step in many idiosyncratic reactions. The drug hypersensitivity syndrome, defined by the presence of fever, rash and internal organ involvement, is estimated to occur in approx 1 in 1000 to 1 in 10,000 exposures with drugs such as anticonvulsants sulfonamide antibiotics, allopurinol, and dapsone. Symptoms usually start within 2-8 wk of drug initiation. Serum sicknesslike reaction, most frequently found after 7-14 d of drug exposure, is distinguished by a fever, cutaneous eruption and arthralgias. Medications such as cefaclor, minocycline and bupropion are most frequently implicated in this reaction. In contrast, drug-induced lupus can occur l-2 yr after initiation of medication. Drug-induced lupus is characterized by musculoskeletal complaints and fever and weight loss. Drugs most commonly associated with drug-induced lupus include procainamide, hydralazine, chlorpromazine, isoniazid, and minocycline. Management of patients who develop idiosyncratic reactions includes discontinuation of the implicated drug, initiation of corticosteroids (when appropriate), and symptomatic relief as required. Internal organ involvement, which may initially be asymptomatic, should be monitored. Confirmatory or diagnostic tests are not readily available in most areas, except for research purposes.

Drug Hypersensitivity↗
PubMed2003

Safety of celecoxib in individuals allergic to sulfonamide: a pilot study.

OBJECTIVE: To evaluate cross reactivity between sulfonamide antimicrobials and celecoxib in patients with histories of allergies to sulfonamide antimicrobials. METHODS: Immunocompetent patients with a history of sulfonamide antimicrobial allergy who were being considered for therapy with celecoxib were prospectively enrolled. Sulfamethoxazole and trimethoprim skin prick and intradermal testing and/or an in vitro lymphocyte toxicity assay were performed. If skin testing was negative, an oral challenge with sulfamethoxazole and trimethoprim was performed. Oral challenges with celecoxib were administered to all patients. RESULTS: Twenty-eight immunocompetent patients (26 female; mean age 60 years) were evaluated. History of sulfonamide antimicrobial allergy included urticaria (n = 7), cutaneous eruptions (n = 9), and other (n = 12). Four of the 28 patients who were skin prick tested were positive to sulfamethoxazole and two of the ten patients who underwent in vitro testing were positive to sulfamethoxazole. All 28 patients were administered celecoxib and tolerated the medication. Phone call follow up in 25 patients disclosed that 15 patients continued to take celecoxib, while five patients did not take celecoxib following the oral challenge, and five discontinued celecoxib due to adverse effects, lack of drug efficacy or physician preference. CONCLUSIONS: Confusion exists regarding the potential for cross reactivity between sulfonamide antimicrobials and other sulfonamide-containing compounds. The six sulfonamide-allergic patients tolerated celecoxib uneventfully. This pilot study supports the hypothesis that the potential for cross-reactivity between celecoxib and sulfonamide antimicrobials appears to be low. However, further investigations are required to confirm this.

Administration, Oral↗
PubMed2003

Drug eruptions: approaching the diagnosis of drug-induced skin diseases.

Adverse drug reactions are a major problem in drug therapy, and cutaneous drug reactions account for a large proportion of all adverse drug reactions. Cutaneous drug reactions are also a challenging diagnostic problem since they can mimic a large variety of skin diseases, including viral exanthema, collagen vascular disease, neoplasia, bacterial infection, psoriasis, and autoimmune blistering disease, among others. Furthermore, determining that a particular medication caused an eruption is often difficult when the patient is taking multiple drugs. In this review, we will describe and illustrate a thoughtful, comprehensive, and clinical approach to the diagnosis and management of adverse cutaneous drug reactions. A morphologic approach to drug eruption includes those that are classified as maculopapular, urticarial, blistering or pustular with or without systemic manifestations. Exanthematous drug eruptions, drug hypersensitivity syndrome, urticaria and angioedema, serum sickness-like reactions, fixed drug eruptions, drug-induced autoimmune blistering diseases, Stevens-Johnson syndrome, toxic epidermal necrolysis, drug-induced acne, acute generalized exanthematous pustulosis, lichenoid drug eruptions and photosensitivity eruptions will be discussed.

Adverse Drug Reaction Reporting Systems↗
PubMed2002

Efavirenz-induced skin eruption and successful desensitization.

OBJECTIVE: To report a patient with efavirenz-induced hypersensitivity syndrome reaction who was successfully desensitized to efavirenz. CASE SUMMARY: A 37-year-old HIV-positive white man was placed on efavirenz, amprenavir, stavudine, lamivudine, and didanosine due to virologic failure with a previous regimen. Eight days into treatment, the patient developed a generalized rash and all medication was discontinued. Two weeks later, he was started on efavirenz, stavudine, didanosine, lamivudine, and lopinavir. The next morning, he awoke with red, itchy skin. All of the medications were discontinued. At the HIV Drug Safety Clinic, the patient was successfully restarted on amprenavir, stavudine, didanosine, lamivudine, and lopinavir. A 14-day desensitization to efavirenz was also undertaken; on day 12 of the desensitization, he once again developed a rash. He was treated symptomatically, and the desensitization protocol was extended. Sixteen months following the successful desensitization, he is tolerating full-dose efavirenz in combination with the other antiretroviral agents. DISCUSSION: The incidence of efavirenz-induced hypersensitivity ranges between 10% and 34%. Generally, an erythematous, maculopapular rash with or without fever develops 1-3 weeks after the initiation of therapy. In many patients without systemic manifestations, an attempt should be made to continue therapy and treat the rash symptomatically. If this fails, desensitization with the implicated drug can be tried. CONCLUSIONS: A history of antiretroviral-induced hypersensitivity reactions often limits the choices of medications that can be used in subsequent treatment regimens. Desensitization may allow for the continued use of previously restricted medications.

Adult↗
PubMed2002

Skin eruption following the use of two Chinese herbal preparations: a case report.

OBJECTIVE: To describe a patient who developed a widespread skin eruption following the use of two Chinese herbal medications, Fang Feng Tong Sheng Wan and Bi Yan Pian. CASE SUMMARY: A 34-year-old man developed widespread erythematous papules that coalesced into plaques after five days of therapy with two Chinese herbal preparations. There was no lymphadenopathy or hepatosplenomegaly, and the patient denied any fever, chills or malaise. The skin biopsy was compatible with a drug eruption. When the patient's oral medications, including the herbal medications, were discontinued, the skin eruption resolved over the next few weeks. All of the regular long term medications were restarted without any sequalae. DISCUSSION: This case, once again, emphasizes that, although herbal medications are marketed as natural products, these products can be associated with adverse drug effects. Other adverse effects that have been implicated with the use of Chinese herbal medications include interstitial fibrosis, renal failure, liver toxicity and severe dermatitis. In addition, there are several cases of adulteration of Chinese herbal products with synthetic medications. CONCLUSION: Although rare, Chinese herbal medications can be associated with serious adverse effects. Clinicians should question patients about the use of herbal products whenever an adverse drug effect is suspected.

Adult↗
PubMed2002

Confirming false adverse reactions to drugs by performing individualized, randomized trials.

One-patient, randomized, double-blind, controlled trials (N-of-1 RCTs) have traditionally been used to assess the efficacy of treatment. At the Drug Safety Clinic, Toronto, this methodology is used to evaluate adverse effects related to medication use, specifically when the symptoms are vague and are in response to more than one medication. Two patients are described with histories of drug allergies to multiple medications; as well, guidelines for conducting N-of-1 trials are summarized. The first patient had a history of prolonged periorbital and generalized weakness lasting up to one week after exposure to a variety of drugs. Because of the ambiguous results of local anesthetic skin testing, an N-of-1 trial was performed using lidocaine without preservative. Two short-lived episodes of blepharospasm and lethargy were observed with placebo; no subjective or objective reaction occurred with active drug. The second patient had a history of prolonged weakness and drowsiness after exposure to many medications; she had been told that she was allergic to all drugs with a benzene ring. During the first N-of-1 trial, generalized weakness was observed with 10 mg of dimenhydrinate and all four placebo doses. During the second N-of-1 challenge using codeine, no unwarranted reactions occurred with either active or placebo drug. Traditional testing of these patients to disprove the clinical symptoms is often difficult because of the anxiety level associated with the patients' past experiences. N-of-1 trials provide a useful alternative for the management of patients with nonspecific symptomatology attributed to drug ingestion.

Administration, Oral↗