Gastrointestinal dysfunction, drugs used

These drugs have low bioavailability, due to the presence of a polar, charged side group. This makes these drugs useful for gastrointestinal dysfunction (e.g., as antiulcer or antispasmodic agents). 

Gastrointestinal complaints (eg, nausea, diarrhea, vomiting, flatulence) are the most common adverse effects but rarely require discontinuation of therapy. Other potential adverse effects include headache and asthenia. Tenofbvir-associated proximal renal tubulopathy causes excessive renal phosphate and calcium losses and 1-hydroxylation defects of vitamin D, and preclinical studies in several animal species have demonstrated bone toxicity (eg, osteomalacia). Monitoring of bone mineral density should be considered with long-term use in those with risk factors for or with known osteoporosis, as well as in children. Reduction of renal function over time, as well as cases of acute renal failure and Fanconi s syndrome, have been reported in patients receiving tenofovir alone or in combination with emtricitabine. For this reason, tenofovir should be used with caution in patients at risk for renal dysfunction. Tenofovir may compete with other drugs that are actively secreted by the kidneys, such as cidofovir, acyclovir, and ganciclovir. 

Of about 50 patients with P-thalassemia who were treated with deferasirox, four (three children and one woman) developed Fanconi syndrome that was probably related to the drug [16 ]. The use of deferasirox (30 mg/kg/day in the children, 38 mg/ kg/day in the adult time to onset not specified) was followed by severe proximal renal tubular dysfunction characterized by hypokalemia, hypophosphatemia, glycosuria, and a metabolic acidosis. All recovered on withdrawal of deferasirox and electrolyte supplementation. The three children simultaneously had mild infections (gastrointestinal in two, respiratory in one) the woman had no other susceptibility factors for tubular dysfunction. 

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