tadalafil

tadalafil

(tah dal' ah fill)

Cialis

Pregnancy Category B

Drug classes

Impotence drug

Phosphodiesterase-5 inhibitor

Therapeutic actions

Selectively inhibits cGMP-specific phosphodiesterase type 5. The mechanism of penile erection involves the release of nitric oxide into the corpus cavernosum of the penis during sexual stimulation. Nitrous oxide activates cGMP, which causes smooth muscle relaxation allowing the flow of blood into the corpus cavernosum.Tadalafil prevents the breakdown of cGMP by phosphodiesterase, leading to increased cGMP levels and prolonged smooth muscle relaxation, promoting the flow of blood into the corpus cavernosum.

Indications

·        Treatment of erectile dysfunction in the presence of sexual stimulation

Contraindications and cautions

·        Contraindicated with allergy to any component of the tablet, concurrent use of nitrates or alpha blockers; contraindicated for use in women or children.

·        Use cautiously with hepatic or renal dysfunction; with anatomical deformation of the penis, with known cardiac disease (effects of sexual activity need to be evaluated), congenital prolonged QT interval, unstable angina; hypotension (systolic < 90); uncontrolled hypertension (> 170/110), severe hepatic impairment; end-stage renal disease with dialysis; hereditary degenerative retinal disorders.

Available forms

Tablets—5, 10, 20 mg

Dosages

ADULTS

10 mg PO taken before anticipated sexual activity; range 5–20 mg PO. Limit use to once per day.

PEDIATRIC PATIENTS

Not intended for use in children.

GERIATRIC PATIENTS

Starting dose of 5 mg PO is suggested.

·        Patients receiving concurrent itraconazole, ketoconazole, ritonavir: Do not exceed one single 10-mg dose in a 72-hr period.

·        Renal impairment (CrCl 31–50): Initial dose not to exceed 5 mg PO daily or 10 mg PO q 48 hr.

·        CrCl < 30 ml/mm: 5 mg PO daily.

·        Hepatic impairment (Child Pugh Class A or B): Maximum dosage should not exceed 10 mg PO daily.

Pharmacokinetics

Route	Onset	Peak
Oral	Rapid	0.5–6 hr

Metabolism: Hepatic, T_1/2: 17.5 hr

Distribution: Not intended for use in women

Excretion: Feces, urine

Adverse effects

·        CNS: Headache, abnormal vision, changes in color vision, fatigue, ischemic optic neuropathy

·        CV: Flushing, angina, chest pain, hypertension, hypotension, MI, palpitation, postural hypotension, tachycardia

·        GI: Dyspepsia, diarrhea, abdominal pain, dry mouth, esophagitis, gastritis, GERD, nausea, abnormal liver function test results

·        GU: Abnormal erection, spontaneous erection, priapism

·        Respiratory: Rhinitis, sinusitis, dyspnea, epistaxis, pharyngitis, nasal congestion

·        Other: Flulike syndrome, edema, pain, rash, sweating, myalgia

Interactions

Drug-drug

·        WARNING: Possible severe hypotension and serious cardiac events if combined with nitrates, alpha blockers; this combination is contraindicated.

·        Possible increased tadalafil levels and effects if taken with ketoconazole, itraconazole, erythromycin; monitor patient and reduce dosage as needed

·        Increased tadalafil serum levels if combined with indinavir, ritonavir; if these drugs are being used, limit tadalafil dose to 10 mg in a 72-hr period

·        Reduced tadalafil levels and effectiveness if combined with rifampin

·        Risk for increased cardiac effects, decreased BP, or flushing if combined with alcohol; warn patient of this possibility if patient uses alcohol

Drug-food

·        Possible increased tadalafil levels if taken with grapefruit juice

Nursing considerations

Assessment

·        History: Allergy to any component of the tablet, concurrent use of nitrates or alpha blockers; unstable angina; hypotension; uncontrolled hypertension; severe hepatic impairment; end-stage renal disease with dialysis; hereditary degenerative retinal disorders; anatomical deformation of the penis, cardiac disease, congenital prolonged QT interval

·        Physical: Orientation, affect; skin—color, lesions; R, adventitious sounds; P, BP, ECG, LFTs, renal function tests

Interventions

·        Ensure diagnosis of erectile dysfunction and determine underlying causes and other appropriate treatment.

·        Advise patient that drug does not work without sexual stimulation. Limit use to once per day.

·        Remind patient that drug does not protect against sexually transmitted diseases and appropriate measures should be taken.

·        WARNING: Advise patient to never take this drug with nitrates or alpha-adrenergic blockers; serious and even fatal complications can occur.

·        Warn patient of the risk of lowered BP or dizziness if drug is taken with alcohol.

Teaching points

·        Take this drug before anticipated sexual activity. The drug will stay in your body for more than 3 days. The drug will have no effect unless there is sexual stimulation.

·        This drug will not protect you from sexually transmitted diseases; use appropriate precautions.

·        Do not take this drug if you are taking any nitrates, alpha blockers, or other drugs for treating erectile dysfunction; serious side effects and even death can occur.

·        Many drugs may interact with tadalafil; always consult your health care provider before taking any drug, including over-the-counter drugs and herbal therapies. Dosage adjustments may be needed.

·        Stop taking the drug and contact your health care provider if you experience sudden loss of vision.

·        Combining this drug with alcohol could cause dizziness, loss of blood pressure, or increased flushing.

·        You may experience these side effects: Headache, dizziness, upset stomach, runny nose, muscle pains. These side effects should go away within a couple of hours. If side effects persist, consult your health care provider.

·        Report difficult or painful urination, vision changes, fainting, erection that persists for longer than 4 hours (if this occurs, seek medical assistance as soon as possible), sudden loss of vision.

Adverse effects in Italic are most common; those in Bold are life-threatening.