MARCH 2002

 

FORMULARY ADDITIONS

 

Tenofovir Disoproxil Fumarate

Viread® (Gilead Sciences, Inc.)

300 mg Tablets

 

Tenofovir disoproxil fumarate (DF) is indicated in combination with other antiretrovirals for the treatment of HIV-1 infection.  Studies were conducted in treatment experienced adults with evidence of HIV-1 viral replication while receiving antiretroviral treatment.  Studies in treatment-naïve patients are ongoing and the risk-benefit for this population has yet to be determined.

A black box warning that accompanies prescribing information states that lactic acidosis and severe hepatomegaly with steatosis, including fatal cases, have been reported with the use of nucleoside analogs alone or in combination with other antiretrovirals.  A majority of these cases have been in women.  Obesity and prolonged nucleoside exposure are risk factors.  Particular caution should be exercised when administering nucleoside analogs to any patient with known risk factors for liver disease; however, cases have also been reported in patients with no known risk factors.  Treatment with tenofovir should be stopped in any patient who develops clinical or laboratory findings suggestive of lactic acidosis or pronounced hepatotoxicity (including hepatomegaly and steatosis even in the absence of marked transaminase elevations). 

Tenofovir DF should not be administered to patients with a creatinine clearance <60 ml/min until data becomes available describing the disposition of tenofovir in these patients.  Because tenofovir is not entirely renally excreted (renal clearance=70-80%), pharmacokinetics may be altered in patients with hepatic insufficiency.

The most common adverse events that occurred were moderate gastrointestinal event such as nausea, vomiting, and flatulence.

Based on the results of in vitro experiments and the known elimination pathway of tenofovir, the potential for CYP450 mediated interactions involving tenofovir with other medicinal products is low. 

Co-administration of tenofovir with other drugs that are eliminated by active tubular secretion may increase serum concentrations of either tenofovir or of the co-administered drug due to competition of the elimination pathway.  Drugs that decrease renal function may also increase serum concentration of tenofovir.

Other drugs that have affected tenofovir peak concentration have included indinavir (increase by 14%) and lopinavir/ritonavir (increased by 31%).  Tenofovir affects peak concentration of didanosine (increase by 28%), lamivudine (decrease by 24%), indinavir (decreased by 11%), and lopinavir/ritonavir (decrease by 28%).  Tenofovir had no effect on efavirenz onset.

 

DRUG AND FOOD INTERACTIONS: Administration of tenofovir following a high fat meal increases the AUC by 40% and the Cmax by approximately 14%.  Food delays the time to Cmax by approximately one hour.  Tenofovir should be taken with a meal to enhance its bioavailability.

 

DOSAGE AND ADMINISTRATION: The dose of tenofovir is 300 mg once daily taken orally with a meal.  If given with didanosine, tenofovir should be administered two hours before or one hour after didanosine.  If overdose occurs, the patient must be monitored for evidence of toxicity and standard supportive treatment given as necessary.  It is not known whether peritoneal or hemodialysis increases the rate of elimination of tenofovir. 

 

 

 

Polyethylene Glycol 3350, NF Powder for Solution

Miralax® (Braintree Laboratories, Inc.)

17 Gram Packets

 

Polyethylene glycol 3350 (Miralax®) powder for oral solution is an osmotic laxative indicated in the treatment of constipation.  Miralax appears to have no effect on the balance of electrolytes and is not associated with tachyphylaxis. 

In patients who are not constipated, Miralax is completely recovered. However, in constipated patients, Miralax recovery is incomplete and highly variable.  Miralax is not fermented into hydrogen or methane by colonic microflora in human feces.  There is no systemic absorption with oral administration.  Onset of effect occurs in two to four days.

Miralax is contraindicated in patients with known or suspected bowel obstruction and in patients who are hypersensitive to polyethylene glycol.  Patients with symptoms suggestive of bowel obstruction (nausea, vomiting, abdominal pain or distention) should be evaluated to rule out obstruction before Miralax is initiated.  All patients who present with complaints of constipation should have a complete medical exam to detect associated metabolic, endocrine, and neurogenic conditions.  In addition, patients should be questioned about any medications they may be taking in order to rule out medication-induced constipation.  Patients should be educated about good defacatory and eating habits (such as high fiber diet and plenty of fluids) and lifestyle changes (regular exercise) which may be helpful to produce more regular bowel habits.

Nausea, abdominal bloating, cramping, and flatulence have been reported to occur with the use of Miralax.  High doses may produce diarrhea and excessive stool frequency.  The elderly are more susceptible to diarrhea as this has occurred in this patient population at the normal recommended dose of 17 grams.

 

DRUG INTERACTIONS: No specific drug interactions have been identified.

 

DRUG AND FOOD INTERACTIONS: Miralax must be mixed with water, juice, soda, coffee, or tea prior to administration.  The manufacturer’s prescribing information lists no drug/food interactions.

 

DOSAGE AND ADMINISTRATION: The usual adult dose for Miralax is one 17gm packet day per day in eight ounces of water, juice, soda, coffee, or tea.  Approximately two to four days may be required to produce a bowel movement.  The safety and effectiveness of Miralax has not been established in pediatric patients. 

 

PREGNANCY:  Category C.  Animal reproductive studies have not been performed with Miralax.  It is not known whether this medication can cause fetal harm when administered to pregnant women or if it can effect reproductive capacity.  Administer with caution only when clearly needed.

 

 

Formulary Additions and Deletions Not Listed in 2001-2002 Formulary Publication

Generic Name

Trade Name

Therapeutic Class

Action

Date

Comments

Amphotericin B Suspension

Fungizone

Antifungal

Deleted

1/8/02

Discontinued by manufacturer

Cefuroxime Axetil

Suspension

Ceftin Suspension

Second Generation Cephalosporin

Added

3/13/01

 

Chloramphenicol Ophthalmic Ointment 1%

Chloromycetin

Ophthalmic Antibiotic

Deleted

3/4/02

 

Colchicine 0.5mg

Colchicine

Antigout

Deleted

1/22/02

 

Colchicine 0.6mg

Colchicine

Antigout

Added

1/2202

 

Crotalide Polyvalent Immune Fab (Ovine)

Crofab

Crotalid antivenin

Added

11/27/01

 

Darbepoetin alfa

Aranesp

Colony stimulating factor

Added

11/27/01

 

Delavirdine

Rescriptor

NNRTI

Deleted

8/29/01

 

Desflurane

Suprane

Inhaled Anesthetic

Added

9/25/01

 

Didanosine

Videx IR

NRTI

Deleted

8/28/01

 

Didanosine

Videx EC

NRTI

Added

8/28/01

 

Divalproex Sodium

Depakote ER

Antimigraine

Added

6/27/01

 

Docusate Sodium with Casanthranol

Peri-Colace softgels

Stool softener/laxative

Added

5/3/01

 

Dofetilide

Tikosyn

Class III antiarrhythmic

Added

6/26/01

Restricted to cardiology

Drotrecogin alfa

Xigris

Recombinant human activated protein C for severe sepsis

Added

11/27/01

Restricted by protocol

Fluticasone with Salmeterol for Inhalation

Advair

Antiasthmatic

Added

6/22/01

 

Hyaluronidase

Wydase

Extravasation antidote

Deleted

7/19/01

Discontinued by manufacturer

Insulin Glargine

Lantus

Insulin

Added

9/25/01

 

Lactobacillus GG

Culturelle

Dietary Supplement

Added

9/25/01

 

Lidocaine 4%

Ela-Max

Topical anesthetic

Added

9/25/01

 

Lomefloxacin

Maxaquin

Antibiotic

Deleted

3/4/02

 

Lopinavir/Ritonavir

Kaletra

Protease inhibitor

Added

8/28/01

 

Loxapine Injection

Loxitane

Antipsychotic

Deleted

8/01/01

 

Metoprolol Succinate

Toprol XL

Antihypertensive

Added

5/3/01

 

Niacin 100mg tablet

Niaspan

Vitamin

Added

3/4/02

 

Ofloxacin

Floxin

Antibiotic

Deleted

3/4/02

 

Oxcarbazepine

Trileptal

Antiepileptic

Added

2/27/01

 

Oxybutynin XL

Ditropan XL

Urinary Antispasmodic

Added

2/27/01

 

Pantoprazole IV

Protonix

Proton pump inhibitor

Added

7/28/01

Restricted per protocol

Perflutren Lipid Microsphere

Definity

Contrast Agent

Added

4/1/02

 

Polyethylene glycol 3350

Miralax

Osmotic Laxative

Added

4/1/02

 

Ramipril

Altace

ACE inhibitor

Added

6/26/01

 

Rapacuronium Injection

Raplon

Neuromuscular blocking agent

Deleted

8/9/01

Discontinued by manufacturer

Saquinavir

Invirase, Fortovase

Protease inhibitor

Deleted

8/29/01

 

Sirolimus 1mg/ml Solution

Rapamune

Immunosuppressant Agent

Deleted

3/4/02

Discontinued by manufacturer

Sodium Tetradecyl Injection

Sotradecol

Sclerosing agent

Deleted

2/19/01

 

Sparfloxacin

Zagam

Antibiotic

Deleted

3/4/02

 

Tenofovir Disoproxil Fumerate

Viread

Antiviral

Added

3/1/02

 

Theophylline IR (100mg & 200mg)

Slophyllin

Antiasthmatic

Deleted

3/4/02

Discontinued by manufacturer

Thioridazine

Mellaril-S

Antipsychotic

Deleted

9/20/01

 

Thymocyte Globulin (rabbit)

Thymoglobulin

Immunosuppressant

Added

3/28/01

 

Valganciclovir

Valcyte

Antiviral

Added

8/28/01

 

Venlafaxine XR

Effexor XR

Antidepressant

Added

6/27/01

 

Vidarabine Ointment

Vira-A

Antiviral

Deleted

8/8/01

 

Warfarin Injectable

Coumadin

Anticoagulant

Added

6/22/01

 

Ziprasidone

Geodon

Atypical antipsychotic

Added

6/26/01

Restricted to psychiatry consult

 

 

 

Prepared by Jared S. Calish, PharmD, Pharmacy Practice Management Resident

3/5/02