Chenodal

Because of the potential hepatoxicity of chenodiol, poor response rate in some subgroups of chenodiol treated patients, and an increased rate of a need for cholecystectomy in other chenodiol treated subgroups, chenodiol is not an appropriate treatment for many patients with gallstones. Chenodiol should be reserved for carefully selected patients and treatment must be accompanied by systematic monitoring for liver function alterations. Aspects of patient selection, response rates and risks versus benefits are given in the insert.

Chenodiol is indicated for patients with radiolucent stones in well-opacifying gallbladders, in whom selective surgery would be undertaken except for the presence of increased surgical risk due to systemic disease or age. The likelihood of successful dissolution is far greater if the stones are floatable or small. For patients with nonfloatable stones, dissolution is less likely and added weight should be given to the risk that more emergent surgery might result form a delay due to unsuccessful treatment. Safety of use beyond 24 months is not established. Chenodiol will not dissolve calcified (radiopaque) or radiolucent bile pigment stones.

The recommended dose range for Chenodiol is 13 to 16 mg/kg/day in two divided doses, morning and night, starting with 250 mg b.i.d. the first two weeks and increasing by 250 mg/day each week thereafter until the recommended or maximum tolerated dose is reached. If diarrhea occurs during dosage buildup or later in treatment, it usually can be controlled by temporary dosage adjustment until symptoms abate, after which the previous dosage usually is tolerated. Dosage less than 10 mg/kg usually is ineffective and may be associated with increased risk of cholecystectomy, so is not recommended.

The optimal frequency of monitoring liver function tests is not known. It is suggested that serum aminotransferase levels should be monitored monthly for the first three months and every three months thereafter during Chenodiol administration. Under NCGS guidelines, if a minor, usually transient elevations (1 ½ to3 three times the upper limit of normal) persisted longer than three to six months. Chenodiol was discontinued and resumed only after the aminotransferase level returned to normal; however, allowing the elevations to persist over such an interval is not know to be safe. Elevations over three times the upper limit of normal require immediate discontinuation of Chenodiol and usually reoccur on challenge.

Serum cholesterol should be monitored at six months intervals. It may be advisable to discontinue Chenodiol if cholesterol rises above the acceptable age-adjusted limit for given patient.

Oral cholecystograms or ultrasonograms are recommend at six to nine month intervals to monitor response. Complete dissolutions should be confirmed by a repeat test after one to three months continued Chenodiol administration. Most patients who eventually achieve complete dissolution will show partial (or complete) dissolution at the first on-treatment test. If partial dissolution is not seen by nine to 12 months, the likelihood of success of treating loner is greatly reduced; Chenodiol should be discontinued if there is no response by 18 months. Safety of use beyond 24 months is not established.

Stone recurrence can be expected within five years in 50% of cases. After confirmed dissolution, treatment generally should be stopped. Serial cholecystograms or ultrasonograms are recommended to monitor for recurrence, keeping in mind that radiolucency and gallbladder function should be established before starting another course of Chenodiol. A prophylactic doses is not established; reduced doses cannot be recommended; stones have recurred on 500 mg/day. Low cholesterol or carbohydrate diets, and dietary bran, have been reported to reduce biliary cholesterol; maintenance of reduced weight is recommended to forestall stone recurrence.

Morphologic studies of liver biopsies taken before and after 9 and 24 months of treatment with chenodiol have shown that 63% of the patients prior to chenodiol treatment had evidence of intrahepatic cholestasis. Almost all pretreatment patients had electron microscopic abnormalities. By the ninth month of treatment, reexamination of two-thirds of the patients showed an 89% incidence of the signs of intrahepatic cholestasis. Two of 89 patients at the ninth month had lithocholate-like lesions in the canalicular membrane, although there were not clinical enzyme abnormalities in the face of continued treatment and no change in Type 2 light microscopic parameters.

Discontinuation of chenodiol because of failure to control diarrhea is to be expected in approximately 3% of patients treated. Steady epigastric pain with nausea typical of lithiasis (biliary colic) usually is easily distinguishable from the crampy abdominal pain of drug-induced diarrhea.

Other less frequent, gastrointestinal side effects reported include urgency, cramps, heartburn, constipation, nausea, and vomiting, anorexic, epigastric distress, dyspepsis, flatulence and nonspecific abdominal pain.

Bile acid sequestering agents, such as cholestyramine and colestipol, may interfere with the action of Chenodiol by reducing its absorption. Aluminum-based antacids have been shown to absorb bile acids in vitro and may be expected to interfere with Chenodiol in the same manner as the sequestering agents. Estrogen, oral contraceptive and collaborate (and perhaps other lipid-lowering drugs) increase biliary cholesterol secretion, and the incidence of cholesterol gallstones hence may counteract the effectiveness of Chenodiol.

Due to its hepatotoxicity, chenodiol can affect the pharmacodynamics of coumarin and its derivatives, causing unexpected prolongation of the prothrombin time and hemorrahages. Patients on concommitant therapy with chenodiol and coumarin or its derivatives should be monitored carefully. If prolongation of prothrombin time is observed, the coumarin dosage should be readjusted to give a prothrombin time 1½ to 2 times normal. If necessary chenodiol should be discontinued