Sections
Hepatic Disease | Gastrointestinal Disease | Renal Disease | Cardiac Disease | Pulmonary Disease | Epilepsy
Excerpt
Hepatic disease lowers the first-pass extraction and biotransformation
of medications. In the presence of liver failure, there is a greater
risk for medication side effects, particularly after oral administration
and with drugs that have a narrow therapeutic index (like tricyclic
antidepressants [TCAs]). Liver disease affects
the ability of medications to bind to proteins and affects the metabolism
of most antidepressants, benzodiazepines like diazepam, and neuroleptics
including haloperidol. With chronic liver failure, there should
be a 25%–50% reduction in dosage because
medications that are not bound to protein are more active. In cases of
acute hepatic disease, alterations in drug dose are not necessary.
When choosing an antidepressant medication, citalopram and fluvoxamine
are less protein bound and therefore more effective than other SSRIs. Clinicians
should avoid carbamazepine, valproate, nefazodone, and the phenothiazines
due to hepatotoxicity. Intravenous drug administration avoids first-pass
metabolism by the CYP450 system and may allow medication doses more
typical for patients with normal hepatic function (Beliles 2000; Shaw and DeMaso 2006).