V
valacyclovir
(Apo-Valacyclovir 
, Valtrex)
Do not confuse valacyclovir with acyclovir or valganciclovir, or Valtrex with Valcyte.
classificationPharmacokinetics
Rapidly absorbed after PO administration. Protein binding: 13%–18%. Rapidly converted by hydrolysis to active compound acyclovir. Widely distributed to tissues, body fluids (including CSF). Primarily eliminated in urine. Removed by hemodialysis. Half-life: (acyclovir) 2.5–3.3 hrs (increased in renal impairment).
Uses
Treatment of herpes zoster (shingles) in immunocompetent adults. Treatment of initial and recurrent genital herpes in immunocompetent adults. Prevention of recurrent genital herpes and reduction of heterosexual transmission of genital herpes. Suppression of genital herpes in HIV-infected pts. Treatment of cold sores, chickenpox in immunocompetent children. OFF-LABEL: Prophylaxis and treatment of cancer-related HSV, VZV.
Lifespan considerations
Side effects
Frequent: Herpes zoster (17%–10%): Nausea, headache. Genital herpes (17%): Headache. Occasional: Herpes zoster (7%–3%): Vomiting, diarrhea, constipation (50 yrs and older), asthenia (loss of strength, energy), dizziness (50 yrs and older). Genital herpes (8%–3%): Nausea, diarrhea, dizziness. Rare: Herpes zoster (3%–1%): Abdominal pain, anorexia. Genital herpes (3%–1%): Asthenia (loss of strength, energy), abdominal pain.
Nursing considerations
Baseline assessment
Question for history of allergies, particularly to valacyclovir, acyclovir. Tissue cultures for herpes zoster, herpes simplex should be obtained before giving first dose (therapy may proceed before results are known). Assess medical history, esp. HIV infection, bone marrow or renal transplantation, renal/hepatic impairment.
Patient/family teaching
• Drink adequate fluids. • Do not touch lesions with fingers to avoid spreading infection to new site. • Genital herpes: Continue therapy for full length of treatment. • Space doses evenly. • Avoid sexual intercourse during duration of lesions to prevent infecting partner. • Valacyclovir does not cure herpes. • Notify physician if lesions recur or do not improve. • Pap smears should be done at least annually due to increased risk of cervical cancer in women with genital herpes. • Initiate treatment at first sign of recurrent episode of genital herpes or herpes zoster (early treatment within first 24–48 hrs is imperative for therapeutic results).
valganciclovir
BLACK BOX ALERT May adversely affect spermatogenesis, fertility. Risk for granulocytopenia, anemia, thrombocytopenia.
Do not confuse Valcyte with Valium or Valtrex, or valganciclovir with valacyclovir.
classificationPharmacokinetics
Well absorbed, rapidly converted to ganciclovir by intestinal mucosal cells and hepatocytes. Widely distributed including CSF, ocular tissue. Slowly metabolized intracellularly. Primarily excreted in urine. Removed by hemodialysis. Half-life: Ganciclovir: 4 hrs (increased in renal impairment).
Precautions
Contraindications: Hypersensitivity to acyclovir, ganciclovir. Cautions: Extreme caution in children because of long-term carcinogenicity, reproductive toxicity. Renal impairment, concurrent nephrotoxic medications, preexisting bone marrow suppression or cytopenias, history of cytopenic reactions to other drugs, elderly (at greater risk for renal impairment).
Lifespan considerations
Pregnancy/Lactation: Effective contraception should be used during therapy; valganciclovir should not be used during pregnancy. Avoid breastfeeding; may be resumed no sooner than 72 hrs after last dose of valganciclovir. Pregnancy Category C. Children: Safety and efficacy not established in those younger than 12 yrs. Elderly: Age-related renal impairment may require dosage adjustment.
Interactions
DRUG: Bone marrow depressants may increase myelosuppression. May increase risk of toxicity of didanosine, mycophenolate. Probenecid may decrease renal clearance, increase concentration. Zidovudine (AZT) may increase risk of hematologic toxicity. HERBAL: None significant. FOOD: All foods maximize drug bioavailability. LAB VALUES: May decrease creatinine clearance, platelet count, neutrophils, Hgb, Hct. May increase serum creatinine.
Indications/routes/dosage
Cytomegalovirus (CMV) retinitis
PO: ADULTS: Initially, 900 mg (two 450-mg tablets) twice daily for 21 days. Maintenance: 900 mg once daily.
Prevention of CMV after transplant
PO: ADULTS, ELDERLY: 900 mg once daily beginning within 10 days of transplant and continuing until 100 days (heart, kidney, or pancreas transplant) or 200 days (kidney transplant) post-transplant. CHILDREN 4 MOS–16 YRS: Once daily based on body surface area (BSA) and creatinine clearance (CrCl) using formula: (Dose = 7 × BSA × CrCl). Maximum: 900 mg/day.
Dosage in renal impairment
Dosage and frequency are modified based on creatinine clearance.
| Creatinine Clearance | Induction Dosage | Maintenance Dosage |
| 60 ml/min or higher | 900 mg twice daily | 900 mg once daily |
| 40–59 ml/min | 450 mg twice daily | 450 mg once daily |
| 25–39 ml/min | 450 mg once daily | 450 mg every 2 days |
| 10–24 ml/min | 450 mg every 2 days | 450 mg twice a wk |
Adverse effects/toxic reactions
Hematologic toxicity, including severe neutropenia (most common), anemia, thrombocytopenia, leukopenia, aplastic anemia, pancytopenia, bone marrow suppression may occur. Retinal detachment occurs rarely. Overdose may result in renal toxicity. May decrease sperm production, fertility.
Nursing considerations
Baseline assessment
Obtain baseline CBC, serum chemistries, renal function, urinalysis. Receive full medication history.
Patient/family teaching
• Valganciclovir provides suppression, not cure, of CMV retinitis. • Frequent blood tests are necessary during therapy because of toxic nature of drug. • Ophthalmologic exam q4–6wks during treatment is advised. • Report any new symptom promptly. • May temporarily or permanently inhibit sperm production in men, suppress fertility in women. • Barrier contraception should be used during and for 90 days after therapy (mutagenic potential). • Avoid handling broken/crushed tablets, oral solution. • Report fever, chills, unusual bleeding/bruising; urinary changes.
valproic acid
(Apo-Divalproex 
, Depacon, Depakene, Depakote, Depakote ER, Depakote Sprinkle, Novo-Divalproex 
, Stavzor)
Do not confuse Depakene with Depakote.
classificationUses
Treatment of simple and complex absence (petit mal) seizures (monotherapy preferred due to unpredictable interactions, increased risk of hepatotoxicity). Adjunctive therapy of multiple seizures (Stavzor). Treatment of manic episodes with bipolar disorders, complex partial seizures. Prophylaxis of migraine headaches. OFF-LABEL: Refractory status epilepticus, diabetic neuropathy.
Lifespan considerationsInteractions
DRUG: Carbapenems (e.g., meropenem), CYP3A4 inducers (e.g., carbamazepine, phenytoin) may decrease concentration/effects. May alter effects of warfarin. May increase concentration of lamotrigine. Topiramate may increase risk of elevated serum ammonia levels. HERBAL: Evening primrose may decrease seizure threshold. FOOD: None known. LAB VALUES: May increase serum LDH, bilirubin, AST, ALT. Therapeutic serum level: 50–100 mcg/ml; toxic serum level: greater than 100 mcg/ml.
Availability (Rx)
Capsules (Depakene): 250 mg. Capsules, Sprinkle (Depakote Sprinkle): 125 mg. Injection, Solution (Depacon): 100 mg/ml. Syrup (Depakene): 250 mg/5 ml.
Capsules, Delayed-Release (Stavzor): 125 mg, 250 mg, 500 mg. 
Tablets, Delayed-Release (Depakote): 125 mg, 250 mg, 500 mg. 
Tablets, Extended-Release (Depakote ER): 250 mg, 500 mg.
Administration/handling
IV
Reconstitution • Dilute each single dose with at least 50 ml D5W, 0.9% NaCl, or lactated Ringer’s.
Rate of Administration • Infuse over 60 min at rate of 20 mg/min or less. • Alternatively, single doses of up to 45 mg/kg given over 5–10 min (1.5–6 mg/kg/min).
Storage • Store vials at room temperature. • Diluted solutions stable for 24 hrs. • Discard unused portion.
PO
• May give without regard to food. Do not mix oral solution with carbonated beverages (may cause mouth/throat irritation). • May sprinkle capsule (Depakote Sprinkle) contents on applesauce and give immediately (do not chew sprinkle beads). • Give delayed-release/extended-release tablets whole. Do not crush, break, open delayed-release capsule (Stavzor). • Regular-release and delayed-release formulations usually given in 2–4 divided doses/day. Extended-release formulation (Depakote ER) usually given once daily.
IV incompatibilities
IV compatibilitiesIndications/routes/dosage
Seizures
PO: ADULTS, ELDERLY, CHILDREN 10 YRS AND OLDER: Initially, 10–15 mg/kg/day in 1–3 divided doses. May increase by 5–10 mg/kg/day at weekly intervals up to 30–60 mg/kg/day. Usual adult dosage: 1,000–2,500 mg/day. (Stavzor): Initially, 10–15 mg/kg/day, may increase by 5–10 mg/kg/day at 1-wk intervals to achieve desired response. Maximum: 60 mg/kg/day.
IV: ADULTS, ELDERLY, CHILDREN: Same frequency as oral dose.
Manic episodes
PO (Depakote): ADULTS, ELDERLY: Initially, 750–1,500 mg/day in divided doses. Maximum: 60 mg/kg/day.
PO (Extended-Release [Depakote ER]): Initially, 25 mg/kg/day once daily. Maximum: 60 mg/kg/day. (Delayed-Release [Stavzor]): Initially, 750 mg/day in divided dose. Titrate to lowest therapeutic dose. Maximum: 60 mg/kg/day.
Prevention of migraine headaches
PO (Extended-Release [Depakote ER]): ADULTS, ELDERLY: Initially, 500 mg/day for 7 days. May increase up to 1,000 mg/day.
PO (Delayed-Release [Depakote]): ADULTS, ELDERLY: Initially, 250 mg twice a day. May increase up to 1,000 mg/day. (Stavzor): 250 mg twice a day. May increase to 1,000 mg/day.
Side effects
Frequent: Epilepsy: Abdominal pain, irregular menses, diarrhea, transient alopecia, indigestion, nausea, vomiting, tremors, fluctuations in body weight. Mania (22%–19%): Nausea, drowsiness. Occasional: Epilepsy: Constipation, dizziness, drowsiness, headache, skin rash, unusual excitement, restlessness. Mania (12%–6%): Asthenia (loss of strength, energy), abdominal pain, dyspepsia (heartburn, indigestion, epigastric distress), rash. Rare: Epilepsy: Mood changes, diplopia, nystagmus, spots before eyes, unusual bleeding/bruising.
Nursing considerations
Baseline assessment
Anticonvulsant: Review history of seizure disorder (intensity, frequency, duration, level of consciousness). Initiate safety measures, quiet dark environment. CBC should be performed before and 2 wks after therapy begins, then 2 wks following maintenance dose. Obtain baseline hepatic function tests. Antimanic: Assess behavior, appearance, emotional status, response to environment, speech pattern, thought content. Antimigraine: Question pt regarding onset, location, duration of migraine, possible precipitating symptoms.
Intervention/evaluation
Monitor serum hepatic function tests, bilirubin, ammonia, CBC. Anticonvulsant: Observe frequently for recurrence of seizure activity. Monitor serum hepatic function tests, CBC. Assess skin for ecchymoses, petechiae. Monitor for clinical improvement (decrease in intensity/frequency of seizures). Antimanic: Question for suicidal ideation. Assess for therapeutic response (interest in surroundings, increased ability to concentrate, relaxed facial expression). Antimigraine: Evaluate for relief of migraine headache and resulting photophobia, phonophobia, nausea, vomiting. Therapeutic serum level: 50–100 mcg/ml; toxic serum level: greater than 100 mcg/ml.
Patient/ family teaching
• Do not abruptly discontinue medication after long-term use (may precipitate seizures). • Strict maintenance of drug therapy is essential for seizure control. • Drowsiness usually disappears during continued therapy. • Avoid tasks that require alertness, motor skills until response to drug is established. • Avoid alcohol. • Carry identification card, bracelet that notes anticonvulsant therapy. • Report nausea, vomiting, lethargy, altered mental status, weakness, loss of appetite, abdominal pain, yellowing of skin, unusual bruising/bleeding. • Report if seizure control worsens, suicidal ideation (depression, unusual changes in behavior, suicidal thoughts) occurs.
valsartan
BLACK BOX ALERT May cause fetal injury, mortality if used during second or third trimester of pregnancy.
Do not confuse Diovan with Zyban, or valsartan with losartan or Valstar.
Fixed-combination(s)
Diovan HCT: valsartan/hydrochlorothiazide (a diuretic): 80 mg/12.5 mg, 160 mg/12.5 mg, 160 mg/25 mg, 320 mg/12.5 mg, 320 mg/25 mg. Exforge: valsartan/amlodipine (a calcium channel blocker): 160 mg/5 mg, 160 mg/10 mg, 320 mg/5 mg, 320 mg/10 mg. Exforge HCT: valsartan/amlodipine (a calcium channel blocker)/hydrochlorothiazide (a diuretic): 160 mg/5 mg/12.5 mg, 160 mg/5 mg/25 mg, 160 mg/10 mg/12.5 mg, 160 mg/10 mg/25 mg, 320 mg/10 mg/25 mg. Valturna: valsartan/aliskiren (a direct renin inhibitor): 160 mg/150 mg, 320 mg/300 mg.
classificationPrecautions
Contraindications: Concomitant use with aliskiren in pts with diabetes. Cautions: Concurrent use of potassium-sparing diuretics or potassium supplements, mild to severe hepatic impairment, unstented bilateral/unilateral renal artery stenosis, renal impairment, significant aortic/mitral stenosis.
Lifespan considerationsInteractions
DRUG: NSAIDs may decrease antihypertensive effect. Potassium-sparing drugs, potassium supplements may increase serum potassium. Diuretics may produce additive hypotensive effects. HERBAL: Ginger, ginseng, licorice may worsen hypertension. Black cohosh, periwinkle may increase antihypertensive effects. FOOD: None known. LAB VALUES: May increase serum bilirubin, AST, ALT, BUN, creatinine, potassium. May decrease Hgb, Hct, WBC.
Nursing considerations
Baseline assessment
Obtain B/P, apical pulse immediately before each dose, in addition to regular monitoring (be alert to fluctuations). If excessive reduction in B/P occurs, place pt in supine position, feet slightly elevated. Question for possibility of pregnancy. Assess medication history (esp. diuretic). Question for history of hepatic/renal impairment, renal artery stenosis, history of severe HF. Obtain baseline chemistries, blood counts.
vancomycin
Do not confuse vancomycin with clindamycin, gentamicin, tobramycin, or Vibramycin.
classificationUses
Systemic: Treatment of infections caused by staphylococcal, streptococcal spp. bacteria. PO: Treatment of antibiotic colitis, pseudomembranous colitis, antibiotic-associated diarrhea produced by C. difficile staphylococcal enterocolitis. OFF-LABEL: Treatment of infections caused by gram-positive organisms in pts with serious allergies to beta-lactam antibiotics; treatment of beta-lactam-resistant gram-positive infections.
Lifespan considerations
Pregnancy/Lactation: Drug crosses placenta. Unknown if distributed in breast milk. Pregnancy Category C (injection), B (PO). Children: Close monitoring of serum levels recommended in premature neonates, young infants. Elderly: Age-related renal impairment may increase risk of ototoxicity, nephrotoxicity; dosage adjustment recommended.
Interactions
DRUG: Aminoglycosides, amphotericin B, cisplatin may increase risk of ototoxicity, nephrotoxicity of parenteral vancomycin. HERBAL: None significant. FOOD: None known. LAB VALUES: May increase BUN. Therapeutic peak serum level: (Not routinely obtained) 20–40 mcg/ml; therapeutic trough serum level: 10–20 mcg/ml. Toxic peak serum level: greater than 40 mcg/ml; toxic trough serum level: greater than 20 mcg/ml.
Administration/handling
IV
ALERT 
Give by intermittent IV infusion (piggyback) or continuous IV infusion. Do not give IV push (may result in exaggerated hypotension or “red man” syndrome).
Reconstitution • For intermittent IV infusion (piggyback), reconstitute each 500-mg vial with 10 ml Sterile Water for Injection (20 ml for 1-g vial) to provide concentration of 50 mg/ml. • Further dilute with D5W or 0.9% NaCl to final concentration not to exceed 5 mg/ml.
Rate of Administration • Administer over 60 min or longer (30 min for each 500 mg recommended). • Monitor B/P closely during IV infusion.
Storage • Reconstituted vials are stable for 14 days at room temperature or if refrigerated. • Diluted solutions are stable for 14 days if refrigerated or 7 days at room temperature. • Discard if precipitate forms.
IV incompatibilities
Albumin, amphotericin B complex (Abelcet, AmBisome, Amphotec), aztreonam (Azactam), cefazolin (Ancef), cefotaxime (Claforan), cefoxitin (Mefoxin), ceftazidime (Fortaz), ceftriaxone (Rocephin), cefuroxime (Zinacef), foscarnet (Foscavir), heparin, nafcillin (Nafcil), piperacillin and tazobactam (Zosyn).
IV compatibilitiesAdverse effects/toxic reactions
Nephrotoxicity (acute kidney injury, acute tubular necrosis, renal failure), ototoxicity (temporary or permanent hearing loss) may occur. “Red man syndrome” or “red neck syndrome” is common adverse reaction characterized by pruritus, urticaria, erythema, angioedema, tachycardia, hypotension, myalgia, maculopapular rash (usually appears on face, neck, upper torso). Cardiovascular toxicity (cardiac depression, arrest) occurs rarely. Onset usually occurs within 30 min of start of infusion, resolves within hrs following infusion. May result from too-rapid rate of infusion.
Nursing considerations
Baseline assessment
Avoid other ototoxic, nephrotoxic medications if possible. Obtain culture, sensitivity test before giving first dose (therapy may begin before results are known).
Intervention/evaluation
Monitor serum renal function tests, I&O. Assess skin for rash. Check hearing acuity, balance. Monitor B/P carefully during infusion. Evaluate IV site for phlebitis (heat, pain, red streaking over vein). Obtain vancomycin peak/trough level as ordered by physician or pharmacist. Therapeutic serum level: peak: 20–40 mcg/ml; trough: 10–20 mcg/ml. Toxic serum level: peak: greater than 40 mcg/ml; trough: greater than 20 mcg/ml.
vandetanib
BLACK BOX ALERT Can prolong QT interval (torsade de pointes and sudden cardiac death reported). Do not use in pts with hypokalemia, hypocalcemia, hypomagnesemia, congenital long QT syndrome. Electrolyte imbalances must be corrected prior to initiating therapy. If medication that prolongs QT interval is needed, more frequent EKG monitoring is recommended. EKGs should be obtained during wks 2–4 and wks 8–12 after starting therapy and 3 mos thereafter. Any dose reduction or interruption related to QT prolongation greater than 2 wks must have frequent EKG monitoring as noted above. Only prescribers and pharmacies certified with restricted distribution program are able to prescribe and dispense.
classificationAction
Inhibits epidermal growth factor (EGF)-stimulated receptor tyrosine kinase phosphorylation in tumor cells and endothelial cells. Inhibits cell migration, proliferation, survival, and angiogenesis (new blood vessel formation). Therapeutic Effect: Inhibits thyroid tumor cell growth and metastasis.
Precautions
Contraindications: Congenital long QT syndrome. Cautions: Pregnancy, concurrent medications that prolong QT interval, strong CYP3A4 inducers, thyroid, cerebrovascular disease, bradyarrhythmias, moderate to severe renal/hepatic impairment, hypertension, uncompensated HF, history of torsade de pointes.
Lifespan considerations
Pregnancy/Lactation: May cause fetal harm. Avoid pregnancy. Must use effective contraception during treatment and for at least 4 mos after treatment. Unknown if distributed in breast milk. Pregnancy Category D. Children: Safety and efficacy not established. Elderly: No age-related precautions noted.
Interactions
DRUG: Medications prolonging QT interval (e.g., azithromycin, amiodarone, clarithromycin, erythromycin, ciprofloxacin, haloperidol) may increase risk of QT prolongation. CYP3A4 inducers (e.g., carbamazepine, oxcarbazepine, phenytoin, rifampin) may decrease concentration/effects. HERBAL: St. John’s wort may decrease effectiveness. FOOD: Grapefruit products may increase risk of torsades, myelotoxicity. LAB VALUES: May decrease WBC, Hgb, neutrophils. May increase serum bilirubin, AST, ALT, creatinine, urine protein. May alter serum calcium, glucose, magnesium, potassium.
Administration/handling
PO
• Give without regard to food. • Do not crush. • May disperse in 2 oz of non-carbonated water and stir for 10 min until tablet is evenly dispersed (will not completely dissolve). May administer dispersion immediately. Can be given via feeding tube. • Direct contact of crushed tablets with skin or mucous membranes should be strictly avoided. If contact occurs, wash thoroughly.
Storage • Contact pharmacy to properly discard out-of-date tablets.
Side effects
Frequent (57%–21%): Diarrhea/colitis, rash, dermatitis acneiform/acne, nausea, headache, fatigue, anorexia, abdominal pain. Occasional (15%–10%): Dry skin, vomiting, asthenia (loss of strength, energy), photosensitivity, insomnia, nasopharyngitis, dyspepsia, cough, pruritus, weight decrease, depression.
Adverse effects/toxic reactions
Prolonged QT interval resulting in torsade de pointes, ventricular arrhythmias, sudden cardiac death have been reported. Frequent diarrhea may result in electrolyte imbalances. Severe skin reactions, including Stevens-Johnson syndrome, have been reported. Interstitial lung disease (ILD) or pneumonitis reported (may result in respiratory-related death). Consider ILD in pts with hypoxia, pleural effusion, cough, dyspnea. Ischemic cerebrovascular events have been reported. Life-threatening events including hypertensive crisis, reversible posterior leukoencephalopathy syndrome (RPLS) have been noted. Adverse reactions resulting in death included respiratory failure/arrest, aspiration pneumonia, cardiac failure, sepsis, GI bleeding.
Nursing considerations
Baseline assessment
Obtain CBC with differential, serum chemistries, magnesium, ionized calcium, TSH, UA, EKG, vital signs. Obtain negative urine pregnancy before therapy. Question for history of congenital long QT syndrome, HF, arrhythmias, hepatic/renal impairment, seizures, CVA, hemorrhagic events, HTN. Obtain full medication history including contraception. Perform full head-to-toe exam including visual acuity, thorough skin assessment.
Intervention/evaluation
Monitor blood levels including electrolytes esp. during episodes of diarrhea. EKG during wks 2–4, wks 8–12, then every 3 mos thereafter. Obtain EKG for palpitations, chest pain, hypokalemia, hyperkalemia, hypocalcemia, bradycardia, ventricular arrhythmias, syncope. Report any respiratory changes including dyspnea, cough (may indicate ILD). Reversible posterior leukoencephalopathy syndrome should be considered in pts with seizures, headache, visual disturbances, confusion, altered mental status. Ophthalmologic exams including slit lamp recommended in pts with visual disturbances.
Patient/family teaching
• Blood levels, EKGs will be routinely monitored. • Strictly avoid pregnancy. Contraception should be taken during treatment and 4 mos after discontinuation. • Changes in mental status, seizures, headache, blurry vision, trouble speaking, one-sided weakness may indicate stroke, high blood pressure crisis, or life-threatening brain swelling. Immediately report any newly prescribed medications. • Do not take herbal products. • Limit exposure to sunlight. • Report any yellowing of skin or eyes, abdominal pain, bruising, black/tarry stools, dark urine, decreased urine output, skin changes. • Report palpitations, chest pain, shortness of breath, dizziness, fainting (may indicate arrhythmia).
vardenafil
Do not confuse Levitra with Kaletra or Lexiva, or vardenafil with sildenafil or tadalafil.
classificationPrecautions
Contraindications: Concurrent use of nitrates in any form. Cautions: Renal/hepatic impairment, left ventricular outflow obstruction, cardiac disease, elderly, prolonged QT interval, anatomical deformation of penis, pts who may be predisposed to priapism (sickle cell anemia, multiple myeloma, leukemia), concurrent use with alpha-adrenergic blockers, CYP3A4 inhibitors, elderly.
Lifespan considerationsInteractions
DRUG: Alpha-adrenergic blockers (e.g., alfuzosin, doxazosin, prazosin, tamsulosin, terazosin), nitrates may significantly lower B/P. CYP3A4 inhibitors (e.g., erythromycin, indinavir, itraconazole, ketoconazole, ritonavir) may increase concentration. HERBAL: None significant. FOOD: High-fat meals delay maximum effectiveness. Grapefruit products may increase concentration, risk of toxicity. LAB VALUES: May increase creatinine kinase, GGTP. May alter AST, ALT.
Indications/routes/dosage
Erectile dysfunction
PO: ADULTS: 10 mg approximately 1 hr before sexual activity. Dose may be increased to 20 mg or decreased to 5 mg, based on pt tolerance. Maximum dosing frequency: Once daily. ELDERLY OLDER THAN 65 YRS: 5 mg. Orally disintegrating tablet: 10 mg 1 hr prior to sexual activity.
varenicline
(Champix 
, Chantix)
classificationAction
Binds to acetylcholine receptors, producing agonist activity, preventing nicotine from binding to specific receptors. Blocks ability of nicotine to stimulate central dopamine system, believed to be mechanism underlying reinforcement/reward experienced with smoking. Therapeutic Effect: Decreases desire to smoke.
Pharmacokinetics
Completely absorbed following PO administration. Absorption unaffected by food, time of day dosing. Maximum plasma concentration: 3–4 hrs; steady-state condition: within 4 days. Protein binding: 20%. Minimal metabolism. Removed by hemodialysis. Primarily excreted unchanged in urine. Half-life: 24 hrs.
Lifespan considerations
Indications/routes/dosage
ALERT Therapy should start 1 wk before stopping smoking.
Smoking deterrent
PO: ADULTS, ELDERLY: Days 1–3: 0.5 mg once daily. Days 4–7: 0.5 mg twice daily. Day 8–end of treatment: 1 mg twice daily. Therapy should last for 12 wks. Pts who have successfully stopped smoking at the end of 12 wks should continue with an additional 12 wks of treatment to increase likelihood of long-term abstinence.
Severe Renal Impairment (creatinine clearance less than 30 ml/min): 0.5 mg once daily. Maximum: 0.5 mg twice daily.
End-Stage Renal Disease, Undergoing Hemodialysis: Maximum: 0.5 mg once daily.
Side effects
Frequent (30%–13%): Nausea, insomnia, headache, abnormal dreams. Occasional (8%–5%): Constipation, abdominal discomfort, fatigue, dry mouth, flatulence, altered taste, dyspepsia (heartburn, indigestion, epigastric pain), vomiting, anxiety, depression, irritability. Rare (3%–1%): Drowsiness, rash, increased appetite, lethargy, nightmares, gastroesophageal reflux disease, rhinorrhea, agitation, mood swings.
classification
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