Allergic reactions, drugs hypersensitivity

One of the primary problems with penicillin drugs is the potential for allergic reactions.65 Hypersensitivity to penicillin is exhibited by skin rashes, hives, itching, and difficult breathing. In some individuals, these reactions may be minor and can often be resolved by changing the type of penicillin or the method of administration. In others, however, penicillin hypersensitivity may be severe and lead to an anaphylactic reaction (severe bronchoconstriction and cardiovascular collapse). 

A hypersensitivity (or allergic) reaction to a drug occurs in some individuals, especially those with a history of allergy to many substances. Signs and symptoms of a hypersensitivity to penicillin are highlighted in Display 7-3. 

Control of severe or incapacitating allergic conditions not controlled by other methods, bronchial asthma (including status asthmaticus), contact dermatitis, atopic dermatitis, serum sickness, drug hypersensitivity reactions... 

Besides such antigen-antibody reactions, which play a critical role in the pathogenesis of many allergic, anaphylactic, and hypersensitivity reactions, histamine also can be released from tissue stores in response to physical stimuli, effects of the so-called histamine liberators, a number of chemical substances, various drugs, and toxins. 

Allergic states Control of severe or incapacitating allergic conditions intractable to conventional treatment in serum sickness and drug hypersensitivity reactions. Parenteral therapy is indicated for urticarial transfusion reactions and acute noninfectious laryngeal edema (epinephrine is the drug of first choice). 

Hypersensitivity reactions Allergic reactions occur in approximately 33% of patients. They are more common at the start of treatment, and occur as generalized rashes or drug fever. Discontinue treatment and reinstitute at a low dosage such as 250 mg/day, with gradual increases. Administering prednisolone 20 mg/day for the first few weeks of penicillamine therapy reduces the severity of these reactions. Antihistamines may control pruritus. 

Hypersensitivity reactions Rarely, severe allergic reactions and anaphylaxis have occurred. Most of these occur within several hours after readministration following prior use of the drug. 

Hypersensitivity reactions Make careful inquiry for a history of hypersensitivity reactions. Monitor patients who have had immediate hypersensitivity reactions to penicillins or cephalosporins. If an allergic reaction occurs, discontinue the drug and institute supportive treatment. Cross-sensitivity with other penicillins or -lactam antibiotics is rare. 

Carbamazepine causes a variety of rashes and other allergic reactions including fever, hepatosplenomegaly, and lymphadenopathy, but the incidence of serious hypersensitivity reactions is rare. Systemic lupus erythematosus can occur, but discontinuation of the drug leads to eventual disappearance of the symptoms. Idiosyncratic hematological reactions to carbamazepine... 

Most anaphylactoid reactions are due to a direct or chemical release of histamine, and other mediators, from mast cells and basophils. Immune-mediated hypersensitivity reactions have been classified as types I-IV. Type I, involving IgE or IgG antibodies, is the main mechanism involved in most anaphylactic or immediate hypersensitivity reactions to anaesthetic drugs. Type II, also known as antibody-dependent hypersensitivity or cytotoxic reactions are, for example, responsible for ABO-incompatible blood transfusion reactions. Type III, immune complex reactions, include classic serum sickness. Type IV, cellular responses mediated by sensitised lymphocytes, may account for as much as 80% of allergic reactions to local anaesthetic. 

Allergic reactions manifesting as fever, urticaria or other rashes, and arthralgia occur in 1-5% of patients taking antithyroid drugs. There has been a report of thiamazole-induced hypersensitivity syndrome associated with reactivation of human herpes virus 6 and cytomegalovirus (57). 

In some patients, cephalosporins may cause an allergic reaction similar to the penicillin hypersensitivity described previously. A cross-sensitivity often exists a patient who is allergic to penicillin drugs will also display hypersensitivity to cephalosporin agents. Other principal adverse effects of cephalosporins include gastrointestinal problems such as stomach cramps, diarrhea, nausea, and vomiting. 

Erythromycins, particularly the estolate, can produce acute cholestatic hepatitis (fever, jaundice, impaired liver function), probably as a hypersensitivity reaction. Most patients recover from this, but hepatitis recurs if the drug is readministered. Other allergic reactions include fever, eosinophilia, and rashes. 

Neuroleptic drugs infrequently produce allergic reactions. There are no reports of anaphylactic reactions, but various skin reactions, for example rashes, photosensitivity, and dermatitis, can be viewed as delayed forms of hypersensitivity. Jaundice and blood dyscrasias (hemolytic anemia, agranulocytosis) are rare and may be types of allergic reactions. 

Adverse effects associated with ocular drugs are not imcommon, bnt serious reactions are extremely rare. These adverse reactions are nsnally manifestations of drug hypersensitivity (allergy) or toxicity. The allergic or toxic reaction usually occurs locally in the ocular tissues. Occasionally, as in erythema multiforme potentiated by sulfonamide agents, adverse reactions can manifest as a systemic response. 

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