In healthy subjects no difference was observed between CYP2D6 extensive metabolizers (EMs) and poor metabolizers (PMs) with respect to oral clearance or elimination half-life. Partial clearance to 4-hydroxy propranolol was significantly higher and to naphthyloxylactic acid was significantly lower in EMs than PMs.

Enantiomers

Of the two enantiomers of propranolol the S-enantiomer blocks beta adrenergic receptors. In normal subjects receiving oral doses of racemic propranolol, S-enantiomer concentrations exceeded those of the R-enantiomer by 40-90% as a result of stereoselective hepatic metabolism.

Special Populations

Pediatric

The pharmacokinetics of InnoPran XL have not been investigated in patients under 18 years of age.

Geriatric

The pharmacokinetics of InnoPran XL have not been investigated in patients over 65 years of age. In a study of 12 elderly (62-79 years old) and 12 young (25-33 years old) healthy subjects, the clearance of S-enantiomer of propranolol was decreased in the elderly. Additionally, the half-life of both the R- and S-propranolol were prolonged in the elderly compared with the young (11 hours vs. 5 hours).

Gender

In a dose-proportionality study, the pharmacokinetics of InnoPran XL were evaluated in 22 male and 14 female healthy volunteers. Following single doses under fasting conditions, the mean AUC and Cmax were about 49% and 16% higher for females across the dosage range. The mean elimination half-life was longer in females than in males (11 hours vs. 7.5 hours).

Race

A study conducted in 12 White and 13 African-American male subjects taking propranolol, showed that at steady state, the clearance of R- and S-propranolol were about 76% and 53% higher in African-Americans than in Whites, respectively.

Renal Insufficiency

The pharmacokinetics of InnoPran XL have not been evaluated in patients with renal insufficiency. In a study conducted in 5 patients with chronic renal failure, 6 patients on regular dialysis, and 5 healthy subjects, who received a single oral dose of 40 mg of propranolol, the peak plasma concentrations (Cmax) of propranolol in the chronic renal failure group were 2 to 3-fold higher (161±41 ng/ml) than those observed in the dialysis patients (47±9 ng/ml) and in the healthy subjects (26±1 ng/ml). Propranolol plasma clearance was also reduced in the patients with chronic renal failure.

Chronic renal failure has been associated with a decrease in drug metabolism via down regulation of hepatic cytochrome P450 activity.

Hepatic Insufficiency

The pharmacokinetics of InnoPran XL have not been evaluated in patients with hepatic impairment. However, propranolol is extensively metabolized by the liver. In a study conducted in 7 patients with cirrhosis and 9 healthy subjects receiving 80-mg oral propranolol every 8 hours for 7 doses, the steady-state unbound propranolol concentration in patients with cirrhosis was increased 3-fold in comparison to controls. In cirrhosis, the half-life increased to 11 hours compared to 4 hours (see PRECAUTIONS).

Drug Interactions

Interactions with Substrates, Inhibitors or Inducers of Cytochrome P-450 Enzymes

Because propranolol's metabolism involves multiple pathways in the cytochrome P-450 system (CYP2D6, 1A2, 2C19), administration of InnoPran XL with drugs that are metabolized by, or affect the activity (induction or inhibition) of one or more of these pathways may lead to clinically relevant drug interactions (see DRUG INTERACTIONS under PRECAUTIONS).

Substrates or Inhibitors of CYP2D6

Blood levels and/or toxicity of propranolol may be increased by administration of InnoPran XL with substrates or inhibitors of CYP2D6, such as amiodarone, cimetidine, delavudin, fluoxetine, paroxetine, quinidine, and ritonavir. No interactions were observed with either ranitidine or lansoprazole.

Substrates or Inhibitors of CYP1A2

Blood levels and/or toxicity of propranolol may be increased by administration of InnoPran XL with substrates or inhibitors of CYP1A2, such as imipramine, cimetidine, ciprofloxacin, fluvoxamine, isoniazid, ritonavir, theophylline, zileuton, zolmitriptan, and rizatriptan.

Substrates or Inhibitors of CYP2C19

Blood levels and/or toxicity of propranolol may be increased by administration of InnoPran XL with substrates or inhibitors of CYP2C19, such as fluconazole, cimetidine, fluoxetine, fluvoxamine, teniposide, and tolbutamide. No interaction was observed with omeprazole.

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