Carbamazepine, skin reactions

CARBAMAZEPINE H2 RECEPTOR BLOCKERS -CIMETIDINE, FAMOTIDINE, RANITIDINE t plasma concentrations of phenytoin and risk of adverse effects including phenytoin toxicity, bone marrow depression and skin reactions Inhibition of metabolism via CYP2C9 and CYP2C19 Use alternative acid suppression (e.g. ranitidine) or warn patients that effects last about 1 week. Consider monitoring carbamazepine levels, and adjust dose as necessaiy... 

Toxic profiles of the common antiepileptics vary. Of these, phenytoin has the narrowest therapeutic index, and toxicity is likely to cause ataxia, diplopia and dysarthria, Measurement of blood levels is necessary. With carbamazepine, patients and carers should report any skin reactions or eruptions, tremor or weight gain, For adverse effects with add-on antiepileptics, see the relevant sections in the text,... 

Carbamazepine (CBZ) is a widely used anticonvulsant that can cause rashes in up to 10% of patients, and in occasional cases this may be the precursor to the development of a hypersensitivity syndrome characterized by systemic manifestations such as fever and eosinophilia (Feeder 1998 Vittorio and Muglia 1995). Rarely, CBZ can induce blistering skin reactions such as Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis, two conditions associated with a high fatality rate (Rzany et al. 1999). There is now increasing laboratory evidence to show that... 

An isolated report describes a 26-year-old woman with cerebral palsy who had been taking phenobarbital 15 mg with carbamazepine 400 mg daily for 12 years to control epilepsy, and who developed fatal toxic epidermal necrolysis 2 weeks after starting oral terbinafine 250 mg daily for tinea corporis. The reasons are not understood, but the authors point out that all three drugs can cause adverse skin reactions (erythema multiforme) and suggest that some synergism may have occurred. It is uncertain whether this was a true interaction or a terbinafine adverse effect. 

Genetic factors associated with severe adverse skin reactions induced by antiepileptic drugs in different ethnic populations have been discussed [80 , 81" ]. Several studies have shown that Han Chinese patients carrying the HLA-B 1502 are at high risk of Stevens-Johnson syndrome or toxic epidermal necrolysis when exposed to carbamazepine. 

Skin Oxcarbazepine is considered to be much less likely than carbamazepine to cause skin reactions, owing to its different metabolic pathway. Oxcctrbazepine-associated Stevens-Johnson syndrome has been described in two Chinese patients with epilepsy, one of whom was positive for HLA-B 1502 [223, 224 ]. 

Adverse reactions to carbamazepine include nystagmus, ataxia, diplopia, particularly if the dosage is raised too fast. Gastrointestinal problems and skin rashes are frequent It exerts an antidiuretic effect (sensitization of collecting ducts to vasopressin water intoxication). 

Considerable concern exists regarding the occurrence of idiosyncratic blood dyscrasias with carbamazepine, including fatal cases of aplastic anemia and agranulocytosis. Most of these have been in elderly patients with trigeminal neuralgia, and most have occurred within the first 4 months of treatment. The mild and persistent leukopenia seen in some patients is not necessarily an indication to stop treatment but requires careful monitoring. The most common idiosyncratic reaction is an erythematous skin rash other responses such as hepatic dysfunction are unusual. 

Skin rash reactions to carbamazepine may resolve in 75% of patients with epilepsy when switched to oxcarbazepine thus,... 

With phenytoin, carbamazepine, phenobarbital, primidone, and lamotrigine, hepatotoxicity usually occurs as part of a hypersensitivity reaction, with skin rashes and fever in the early weeks of treatment. More rarely, hepatic disease can develop after many years without signs of hypersensitivity. Once hepatotoxicity develops, mortality... 

Hypersensitivity reactions are relatively common with carbamazepine. Most affect the skin, but systemic reactions with fever, lymphadenopathy, and/or involvement of the bone-marrow, the liver, the heart, the gastrointestinal system, the lungs, and other organs have been described. Severe serum sickness associated with immunoblastic lymphadenopathy has been reported in one case (SED-13, 148) (64). Occasional cases of systemic lupus erythematosus have occurred within the first few months, although an unusual case with onset after 8 years has been described (SEDA-22, 83). 

Another noteworthy adverse drug reaction (ADR) with a higher incidence in Asian patients on the anticonvulsant drugs carbamazepine and phenytoin is the Stevens-Johnson syndrome (SJS) (Locharernkul et al., 2008). SJS is a serious and potentially life-threatening skin condition. There is a conjecture that this higher risk in SJS is associated with a higher presence of the HLA-B 1502 allele in the Asian population. Phillips et al. (2011) argued that carriers of this allele could also avoid other structurally similar anticonvulsants. 

Skin Drug reactions with eosinophilia and systemic symptoms (DRESS) in patients taking carbamazepine have been reported [83" ]. Involvement of internal organs was often characterized by liver injury [84, 85 n. 

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