Enzalutamide-warfarin interaction necessitating warfarin dosage adjustment: A case report of successful clinical management.

WHAT IS KNOWN AND OBJECTIVES: Enzalutamide package labeling recommends avoiding concurrent warfarin use due to potential reductions in warfarin concentrations via enzalutamide-associated hepatic enzyme induction. A case of successful management of this interaction via warfarin adjustments is reported. CASE DESCRIPTION: A 77-year-old Caucasian male, previously relatively stable on warfarin 42-45 mg weekly, reported to clinic after the recent start of enzalutamide and subsequent hospitalization with a subtherapeutic International Normalized Ratio (INR). A 50% increase in weekly warfarin dose resulted in a therapeutic INR. Enzalutamide was temporarily discontinued, and a 33% weekly warfarin dose decrease resulted in two therapeutic INRs. WHAT IS NEW AND CONCLUSION: This is the first case to highlight the clinical significance of this interaction, noting that patients taking enzalutamide may require approximately 30%-50% adjustment in their warfarin dosage to maintain a therapeutic INR.

Are there gender differences in the use of peak flow meters?

To determine if there are gender differences in correct use of peak flow meters (PEM), third-year doctor of pharmacy students (n = 83; 52 females, 31 males) were instructed in a classroom on correct use of a PFM, including demonstrations. Students were then immediately divided into five groups, given a PFM, and assessed for three attempts in private individual sessions. Males had superior performance on the first attempt for total score (p < 0.05) and for "inhale fully" (p < 0.05). On the second attempt, the total score was not different, but males scored higher on "exhale as fast and as hard as you can" (p < 0.05). Controlled gender studies examining use of PFM in adult and pediatric patients with asthma are warranted.

Nocturnal asthma uncontrolled by inhaled corticosteroids: theophylline or long-acting beta2 agonists?

Asthma is an inflammatory disease of the airways that is frequently characterised by marked circadian rhythm. Nocturnal and early morning symptoms are quite common among patients with asthma. Increased mortality and decreased quality of life are associated with nocturnal asthma. Although numerous mechanisms contribute to the pathophysiology of nocturnal asthma, increasing evidence suggests the most important mechanisms relate to airway inflammation. According to international guidelines, patients with persistent asthma should receive long term daily anti-inflammatory therapy. A therapeutic trial with anti-inflammatory therapy alone (without a long-acting bronchodilator) should be assessed to determine if this therapy will eliminate nocturnal and early morning symptoms. If environmental control and low to moderate doses of inhaled corticosteroids do not eliminate nocturnal symptoms, the addition of a long-acting bronchodilator is warranted. Long-acting inhaled beta2 agonists (e.g. salmeterol, formoterol) are effective in managing nocturnal asthma that is inadequately controlled by anti-inflammatory agents. In addition, sustained release theophylline and controlled release oral beta2 agonists are effective. In patients with nocturnal symptoms despite low to high doses of inhaled corticosteroids, the addition of salmeterol has been demonstrated to be superior to doubling the inhaled corticosteroid dose. In trials comparing salmeterol with theophylline, 3 studies revealed salmeterol was superior to theophylline (as measured by e.g. morning peak expiratory flow, percent decrease in awakenings, and need for rescue salbutamol), whereas 2 studies found the therapies of equal efficacy. Studies comparing salmeterol to oral long-acting beta2 agonists reveal salmeterol to be superior to terbutaline and equivalent in efficacy to other oral agents. Microarousals unrelated to asthma are consistently increased when theophylline is compared to salmeterol in laboratory sleep studies. In addition to efficacy data, clinicians must weigh benefits and risks in choosing therapy for nocturnal asthma. Long-acting inhaled beta2 agonists are generally well tolerated. If theophylline therapy is to be used safely, clinicians must be quite familiar with numerous factors that alter clearance of this drug, and they must be prepared to use appropriate doses and monitor serum concentrations. Comparative studies using validated, disease specific quality of life instruments (e.g. Asthma Quality of Life Questionnaire) have shown long-acting inhaled beta2 agonists are preferred to other long-acting bronchodilators. Examination of costs for these therapeutic options reveals that evening only doses of long-acting oral bronchodilators are less expensive than multiple inhaled doses. However, costs of monitoring serum concentrations, risks, quality of life and otheroutcome measures must also be considered. Long-acting inhaled beta2 agonists are the agents of choice for managing nocturnal asthma in patients who are symptomatic despite anti-inflammatory agents and other standard management (e.g. environmental control). These agents offer a high degree of efficacy along with a good margin of safety and improved quality of life.

Thrombocytopenia associated with octreotide.

A 42-year-old woman with a history of hepatitis C-induced cirrhosis, gastrointestinal bleeding, and alcohol abuse presented to the hospital with hematemesis and melena. Based on our previous experience, octreotide (Sandostatin) therapy was started at 50 mg/hr and continued for 5 days. Platelet count on admission (122 x 10(9)/L) dropped immediately after octreotide therapy was started; upon discontinuation, platelet count began trending up from 72 x 10(9)/L. However, octreotide was not suspected at this point as the cause of thrombocytopenia. In a subsequent admission, octreotide was again administered with a resultant prompt decrease in platelet count. To our knowledge, this is only the second case report of octreotide-induced thrombocytopenia, and the first case of this adverse effect demonstrated by inadvertent rechallenge.

Effect of a brief educational intervention on medical students' use of asthma devices.

Several studies have shown that a significant percentage of housestaff and attending physicians are deficient in both skill and knowledge of the metered-dose inhaler (MDI). There are no studies involving medical students, or any including the peak flow meter (PFM). The setting was a large health science center with investigators in private conference rooms with individual medical students. Twenty-two medical students in the last semester before graduation were scored in the use of these devices pre-education and post-education (instruction included both discussion and demonstration). Results revealed a lack of skill initially, followed by dramatic improvement after the intervention. The total number of correct steps for each device (MDI with spacer and PFM) improved significantly (p < 0.0001). This group of medical students was deficient in the use of common asthma devices. A short educational intervention was effective in improving skill.

Gender differences in metered-dose inhaler-spacer device technique.

STUDY OBJECTIVE: To determine whether gender affects the correct use of a metered-dose inhaler (MDI)-spacer device. DESIGN: Prospective, observational study. SETTING: University classrooms. PATIENTS: Eighty-three students in their third year of a Doctor of Pharmacy program. INTERVENTION: Students were given the device and received 20 minutes of education on its use. They then were asked to perform the technique. Assessment and retraining were done, as necessary, by clinicians who were experienced with the device. Students returned 1 week later to perform the technique again. MEASUREMENTS AND MAIN RESULTS: The performance of men versus women was analyzed with chi 2 tests and the Student's t test. Power analysis indicated that 30 students were needed in each group. CONCLUSION: There were no significant differences between men and women in proper MDI-spacer technique.

Response to warfarin and other oral anticoagulants: effects of disease states.

BACKGROUND: Warfarin is associated with numerous drug and food interactions, and much attention has been appropriately focused on this subject. Because several disease states may also affect response to oral anticoagulants, we present a summary of the literature. METHODS: We searched MEDLINE for original articles on the effect of disease states on response to warfarin. RESULTS: Liver disease and thyroid dysfunction are well-documented as affecting warfarin response. Further study is needed to establish whether febrile illness, congestive heart failure, and other disease states enhance the effect of warfarin in some patients. CONCLUSION: Careful monitoring of anticoagulant therapy in patients with diseases that have the potential to affect warfarin response could increase safety and efficacy of this important agent.

Importance of beta(2)adrenergic receptor genotype, gender and race on albuterol-evoked bronchodilation in asthmatics.

To determine whether race and gender affect beta(2)receptor-stimulated bronchodilation, we quantified FEV(1)and plasma concentrations of albuterol at various times following the oral administration of a single 8-mg dose of albuterol in 15 black and 15 white male and female asthmatics. No important racial or gender differences in albuterol-evoked FEV(1)or percent-predicted FEV(1)were evident, although females tended to be more sensitive compared to males. Pharmacodynamic (PD) models were fitted to data in 19 patients (63%); FEV(1)was too erratic to fit in three, and a clockwise hysteresis in the FEV(1)vs. albuterol concentration relationship was observed in eight asthmatics. Mean +/- SD baseline (E(0)), maximal FEV(1)(E(max)) and C(50)were: 3.18 + 1.03 l, 4.00 +/- 1.12 l, 7.84 +/- 10.2 microg/l, respectively. beta(2)receptor genotype was determined in 16 patients. All Arg 16 homozygotes exhibited proportional FEV(1)response vs. plasma albuterol concentration relationships, and thus were fitted by PD models. All those having a poor FEV(1)vs. albuterol concentration relationship carried the Gly 16 allele. We conclude that receptor genotype, but not race or gender, is an important determinant of albuterol pharmacodynamics.

Effect of disease states on theophylline serum concentrations: are we still vigilant?

The use of theophylline has decreased over the past decade because of concerns over the risks of serious adverse effects as well as availability of more effective, safer drugs. Because of this decline in use, some clinicians may not be alert to the marked effect of some disease states on theophylline serum concentrations. The purpose of this review is to heighten awareness of the effect of decompensated heart failure, cor pulmonale, hepatic dysfunction, thyroid disease, and febrile illness on theophylline serum concentrations. Because many patients receive some benefit from this drug, safe use by clinicians requires closer monitoring of serum concentrations in patients with factors that alter theophylline clearance, including several disease states.

Interaction between rifampin and levothyroxine.

Rifampin is a potent inducer of hepatic enzymes and is well documented to cause many clinically significant drug interactions. Studies in normal volunteers have shown its ability to decrease circulating levels of thyroid hormone, while having no effect on thyroid-stimulating hormone (TSH). Reports of rifampin's effects on patients on hormone replacement in the clinical setting are of interest since we believe only one such case has been described. We report the case of a man, stable on levothyroxine, who exhibited significantly elevated TSH levels during therapy with rifampin. Thyroid-stimulating hormone levels returned to baseline 9 days after discontinuance of rifampin.

Impact of genetic polymorphisms of the beta2-adrenergic receptor on albuterol bronchodilator pharmacodynamics.

OBJECTIVE: To determine whether genetic polymorphisms of the beta2-adrenergic receptor gene affect the relationship between albuterol (INN, salbutamol) plasma concentrations and the forced expiratory volume in 1 second (FEV1) in subjects with moderate asthma. METHODS: Sixteen clinically stable patients with moderate asthma who participated in a pharmacokinetic-pharmacodynamic study of albuterol volunteered to provide a blood sample for determination of beta2-adrenergic receptor genotype. FEV1 and plasma concentrations of albuterol were determined at various times after administration of an oral solution that contained 8 mg albuterol. Patients withheld inhaled beta2-agonist and corticosteroid therapy 12 and 24 hours, respectively, before the study. beta2-Adrenergic receptor genotype was determined by polymerase chain reaction with allele-specific oligonucleotide hybridization. RESULTS: Albuterol-evoked FEV1 was higher and the response was more rapid in Arg16 homozygotes compared with the cohort of carriers of the Gly16 variant: Maximal percentage increase in FEV1 (%deltaFEV1), 18% versus 4.9% (P < .03); area under FEV1 albuterol concentration curve, 194%.mL/ng versus 30%.mL/ng (P < .05); initial slope (dE/dC), 1.43%.mL/ng versus 0.55%.mL/ng (P < .003). CONCLUSIONS: The beta2-adrenergic receptor gene polymorphism is a major determinant of bronchodilator response to albuterol. Future pharmacodynamic studies of beta2-agonists should include determination of 02-adrenergic receptor genotype.

Isoniazid drug and food interactions.

Isoniazid inhibits the metabolism of several drugs, resulting in clinically significant interactions in some patients. Clinical trials and case reports have documented that isoniazid can cause increased phenytoin and carbamazepine serum concentrations and toxicity. In relatively high doses, isoniazid can also cause increased effect of theophylline and warfarin. Isoniazid inhibits metabolism of selected benzodiazepines and vitamin D. Inhibition of monoamine oxidase and histaminase by isoniazid can cause significant drug-food interactions. Food greatly decreases isoniazid bioavailability. Although probably best recognized as an inhibitor of drug metabolism, isoniazid has a biphasic effect of inhibition-induction on one cytochrome P450 isozyme, CYP2E1, which partially explains the interaction with acetaminophen and increased risk of hepatotoxicity. Continued investigations will likely result in discovery of new isoniazid interactions.

Effects of gender and race on albuterol pharmacokinetics.

We evaluated the effects of race and gender on albuterol pharmacokinetics in 30 patients with moderate asthma (15 blacks, 15 whites, 16 men, 14 women). Subjects received a single dose of albuterol 8 mg oral solution and had blood samples collected at various times for 12 hours after the dose. Albuterol plasma concentrations were determined by HPLC with fluorescence detection, and pharmacokinetics were determined by compartmental analysis. The apparent volume of distribution of albuterol was significantly higher in men than in women (631+/-171 and 510+/-109 L, respectively, p<0.05). Consequently, the maximum concentration was lower in men than women (10.3+/-2.1 and 12.0+/-1.9 ng/ml, respectively, p<0.05). Elimination rates were 0.136+/-0.008 and 0.160+0.012 hour(-1), respectively (p<0.10). When corrected for ideal body weight, apparent volume of distribution was not different by gender. No differences between blacks and whites other than lag time were noted in albuterol kinetics. The greater apparent volume of distribution in men is likely explained by differences in ideal body weight or lean body mass.

Clinical and economic outcomes in the hypertension and COPD arms of a multicenter outcomes study.

OBJECTIVE: To evaluate the impact of pharmaceutical care on selected clinical and economic outcomes in patients with hypertension or chronic obstructive pulmonary disease (COPD) in ambulatory care settings. DESIGN: Clinic patients with hypertension or COPD were randomly assigned to a treatment group (pharmaceutical care) or a control group (traditional pharmacy care) over a six-month period. Clinical pharmacists and pharmacy residents conducted the protocols. There were 133 evaluable patients (63 treatment and 70 control) in the hypertension study arm and 98 evaluable patients (43 treatment and 55 control) in the COPD study arm. SETTING: 10 Departments of Veterans Affairs medical centers and 1 academic medical center. INTERVENTIONS: Patient-centered pharmaceutical care model (employing standardized care) implemented by clinical pharmacy residents. MAIN OUTCOME MEASURES: Patient knowledge, medication compliance, and health resource use. RESULTS: The hypertension treatment group had a significantly greater reduction in systolic blood pressure from visit 1 to visit 5 than did the control group. In the COPD study arm, trends were positive in the treatment group for patients ratings of symptom interference with activities and dyspnea measures. There was a significant difference between the hypertension treatment and control group for compliance. There were no significant changes in compliance scores in the COPD study arm. Mean number of hospitalizations and other health care provider visits was higher for the hypertension control group. For patients with COPD, hospitalizations increased in the control group, and the number of other health care provider visits was higher in the control group. CONCLUSION: Pharmacists' participation in a pharmaceutical care program resulted in disease state improvement in ambulatory patients with hypertension and COPD.

Update on rifampin drug interactions, III.

Rifampin is a potent inducer of cytochrome P-450 oxidative enzymes. Examples of well-documented, clinically significant interactions include warfarin, oral contraceptives, cyclosporine, glucocorticoids, ketoconazole, theophylline, quinidine, digitoxin, and verapamil. Recent reports have demonstrated clinically relevant interactions with protease inhibitors, zidovudine, delavirdine, itraconazole, nifedipine, midazolam or triazolam, nortriptyline, and doxycycline. To avoid reduced therapeutic response, therapeutic failure, or toxic reactions when rifampin is added to or discontinued from medication regimens, clinicians need to be cognizant of these interactions. Enhanced knowledge of known interactions will continue to develop, including research on induction of specific cytochrome P-450 isoenzymes. New rifampin interactions will be discovered with further investigations.