Understanding Fever and OTC Treatments

Study Notes

Fever is caused by the activation of immune cells, leading to an increase in body temperature. This can be due to exogenous pyrogens released by macrophages and lymphocytes, or endogenous pyrogens like interleukins, interferons, and tumor necrosis factor.
Clinical presentation of fever includes symptoms such as headache, diaphoresis, generalized malaise, chills, tachycardia, arthralgia, myalgia, irritability, anorexia, and elevated body temperature.
Medications can induce hyperthermia as a side effect, including antimicrobials such as aminoglycosides, amphotericin B, cephalosporins, clindamycin, chloramphenicol, imipenem, isoniazid, linezolid, macrolides, mebendazole, vancomycin, antineoplastics like bleomycin, chlorambucil, cytarabine, daunorubicin, hydroxyurea, LAsparaginase, 6-Mercaptopurine, procarbazine, streptozocin, cardiovascular drugs such as epinephrine, hydralazine, methyldopa, nifedipine, procainamide, quinidine, streptokinase, CNS agents like amphetamines, barbiturates, benztropine, carbamazepine, haloperidol, lithium, nomifensine, phenytoin, phenothiazines, serotonin-noradrenaline reuptake inhibitors, tricyclic antidepressants, sumatriptan, thioridazine, trifluoperazine, topiramate, zonisamide, monoamine oxidase inhibitors, and other agents like allopurinol, atropine, azathioprine, cimetidine, corticosteroids, folate, inhaled anesthetics, interferon, iodides, metoclopramide, propylthiouracil, prostaglandin E2, salicylates, tolmetin, etc.
To accurately detect fever, a thermometer must be used to measure the core temperature, which can be estimated using various sites such as rectal, oral, axillary, tympanic, or temporal.
Core temperature should be measured consistently using the same thermometer and site throughout an illness, as readings may vary up to 2.5°F (1.4°C) depending on the site and individual body temperature.
Diagnosis of fever is based on a temperature above the normal range, which varies by measurement site and age. For example, a rectal temperature above 100.4°F (38.0°C), an oral temperature above 99.5°F (37.5°C), or an axillary temperature above 99°F (37.2°C) may indicate fever.
Recommended temperature measurement sites by age include rectal for infants under 3 months, rectal, oral, or temporal for children aged 3-36 months, and oral, tympanic, or temporal for children over 3 years of age.
Complications of fever include dehydration, change in mental status, seizures, and febrile seizures in infants or children without an intracranial infection, metabolic disturbance, or other defined cause.
Treatment of fever includes self-management with antipyretics, nondrug measures, medical referral, and prescription of antipyretic agents based on patient factors and preferences. Exclusion criteria for self-management include age under 3 months with rectal temperature above 100.1°F (38°C), age over 3 months with rectal temperature above 104°F (40°C), symptoms that are not self-limiting, increased risk of hyperthermia, impaired oxygen utilization, or impaired immune function.