Chlorthalidone and related drugs may decrease serum PBI levels without signs of thyroid disturbance.
No information is available.
Reproduction studies have been performed in the rat and the rabbit at doses up to 420 times the human dose and have revealed no evidence of harm to the fetus due to chlorthalidone. There are, however, no adequate and well-controlled studies in pregnant women. Because animal reproduction studies are not always predictive of human response, this drug should be used during pregnancy only if clearly needed.
Thiazides cross the placental barrier and appear in cord blood. The use of chlorthalidone and related drugs in pregnant women requires that the anticipated benefits of the drug be weighed against possible hazards to the fetus. These hazards include fetal or neonatal jaundice, thrombocytopenia, and possibly other adverse reactions that have occurred in the adult.
Thiazides are excreted in human milk. Because of the potential for serious adverse reactions in nursing infants from chlorthalidone, a decision should be made whether to discontinue nursing or to discontinue the drug, taking into account the importance of the drug to the mother.
Safety and effectiveness in children have not been established.
Clinical studies of the 15 mg chlorthalidone tablets did not include sufficient numbers of subjects aged 65 and over to determine whether they respond differently from younger subjects. Other reported clinical experience with 15 mg chlorthalidone tablets has not identified differences in responses between the elderly and younger patients. In general, dose selection for an elderly patient should be cautious, usually starting at the low end of the dosing range, reflecting the greater frequency of decreased hepatic, renal or cardiac function, and of concomitant disease or other drug therapy.
This drug is known to be substantially excreted by the kidney, and the risk of toxic reactions to this drug may be greater in patients with impaired renal function. Because elderly patients are more likely to have decreased renal function, care should be taken in dose selection, and it may be useful to monitor renal function.
The following adverse reactions have been observed, but there is not enough systematic collection of data to support an estimate of their frequency.
Gastrointestinal System Reactions: anorexia, gastric irritation, nausea, vomiting, cramping, diarrhea, constipation, jaundice (intrahepatic cholestatic jaundice), pancreatitis.
Central Nervous System Reactions: dizziness, vertigo, paresthesias, headache, xanthopsia.
Hematologic Reactions: leukopenia, agranulocytosis, thrombocytopenia, aplastic anemia.
Dermatologic-Hypersensitivity Reactions: purpura, photosensitivity, rash, urticaria, necrotizing angiitis (vasculitis, cutaneous vasculitis), Lyell’s syndrome (toxic epidermal necrolysis).
Cardiovascular Reactions: orthostatic hypotension may occur and may be aggravated by alcohol, barbiturates, or narcotics.
Other Adverse Reactions: hyperglycemia, glycosuria, hyperuricemia, muscle spasm, weakness, restlessness, impotence.
Whenever adverse reactions are moderate or severe, chlorthalidone dosage should be reduced or therapy withdrawn.
Symptoms of acute overdosage include nausea, weakness, dizziness, and disturbances of electrolyte balance. The oral LD 50 of the drug in the mouse and the rat is more than 25,000 mg/kg body weight. The minimum lethal dose (MLD) in humans has not been established. There is no specific antidote, but gastric lavage is recommended, followed by supportive treatment. Where necessary, this may include intravenous dextrose-saline with potassium, administered with caution.
Therapy should be initiated with the lowest possible dose, then titrated according to individual patient response. A single dose given in the morning with food is recommended; divided daily doses are unnecessary.
Therapy, in most patients, should be initiated with a single daily dose of 15 mg. If the response is insufficient after a suitable trial, the dosage may be increased to a single daily dose of 25 mg. If additional control is required, the dosage of chlorthalidone may be increased to 30-50 mg once daily or 100 mg once daily. A second antihypertensive drug (step 2 therapy) may be added, as necessary. Dosage above 100 mg daily usually does not increase effectiveness. Increases in serum uric acid and decreases in serum potassium are dose-related over the 15-100 mg/day range.
Maintenance doses may be lower than initial doses and should be adjusted according to individual patient response. Effectiveness is well sustained during continued use.
Adults, initially 30 to 100 mg daily, or 100 mg on alternate days. Some patients may require 90 to 200 mg at these intervals or up to 200 mg daily. Dosages above this level, however, do not usually produce a greater response.
Maintenance doses may often be lower than initial doses and should be adjusted according to individual patient response. Effectiveness is well sustained during continued use.
Chlorthalidone Tablets, USP are available containing 25 mg of chlorthalidone, USP.
The 25 mg tablets are light yellow, round, unscored tablets debossed with M35 on one side of the tablet and blank on the other side. They are available as follows:
bottles of 30 tablets
Store at 20° to 25°C (68° to 77°F). [See USP for Controlled Room Temperature.]
Protect from light.
Dispense in a tight, light-resistant container as defined in the USP using a child-resistant closure.
Biochemical studies in animals have suggested reasons for the prolonged effect of chlorthalidone. Absorption from the gastrointestinal tract is slow due to its low solubility. After passage to the liver, some of the drug enters the general circulation, while some is excreted in the bile, to be reabsorbed later. In the general circulation, it is distributed widely to the tissue, but is taken up in highest concentrations by the kidneys, where amounts have been found 72 hours after ingestion, long after it has disappeared from other tissues. The drug is excreted unchanged in the urine.
Mylan Pharmaceuticals Inc.
Morgantown, WV 26505 U.S.A.
Mylan Laboratories Limited
Hyderabad — 500 096, India
| CHLORTHALIDONE |
|Labeler — PD-Rx Pharmaceuticals, Inc. (156893695)|
|Registrant — PD-Rx Pharmaceuticals, Inc. (156893695)|
|PD-Rx Pharmaceuticals, Inc.||156893695||repack (55289-067)|
Revised: 05/2022 PD-Rx Pharmaceuticals, Inc.
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