Also suspected of having this effect are cimetidine, ranitidine, and acetaminophen (paracetamol). Cimetidine, rifampicin, and thioridazine cause interactions with zaleplon. Gastrointestinal symptoms were epidemiologically associated with use of antacids or cimetidine. Its toxicity is increased by erythromycin, cimetidine, and fluoroquinolones, such as ciprofloxacin. Others include amsacrine, 6,6'-azopurine, chlorpromazine, cimetidine, cyanide, diethylstilbestrol, genestein, isovanillin, and methadone. Cimetidine may influence the absorption of doxepin. The drug cimetidine heightens praziquantel bioavailability. More recent examples are cimetidine and loratadine in the United States, and ibuprofen in Australia. Rarely, interstitial nephritis, urticaria, and angioedema have been reported with cimetidine treatment. The anti-ulcer drug cimetidine is generated using such reactivity. The commercial name "Tagamet" was decided upon by fusing the two words "antagonist" and "cimetidine". Treatments showing no discernable value included N-acetylcysteine, benzylpenicillin, cimetidine, thioctic acid, and silybin. It is metabolized in the liver into cimetidine sulfoxide, hydroxycimetidine, and guanyl urea cimetidine. Creatinine clearance exceeds GFR due to creatinine secretion, which can be blocked by cimetidine. The oral bioavailability of cimetidine is 60 to 70%.