Para-Time SR

Vasodilating agent;180 181 a benzylisoquinoline alkaloid180 181 a prepared synthetically or obtained from opium.a

Administration

Administer orally, or by IM or slow IV injection.180 181 a

Has been used intra-arterially in treatment of acute vascular occlusion in conjunction with anticoagulants.a

Has been administered by intracavernous† injection for the treatment of erectile dysfunction.103 105 106 107 108 110 112 113 114 115 116 118 119 120 121 122 123 124 125 126 127

IV Administration

Slow IV injection preferred when an immediate effect is desired.181 a

Inject slowly over a 1- to 2-minute period to minimize serious adverse effects (e.g., arrhythmias, fatal apnea).181 a (See Cardiovascular and Respiratory Effects under Cautions.)

Dosage

Available as papaverine hydrochloride; dosage expressed in terms of salt.180 181

Pediatric Patients

6 mg/kg daily (as 4 divided doses).a

Adults

Usually, 150 mg (extended-release capsules) every 8–12 hours.180 a

Alternatively, 300 mg (extended-release capsules) every 12 hours.a

75–300 mg (conventional tablets [no longer commercially available in US] 3–5 times daily, also has been used.a

Usually, 30 mg; may repeat 30–120 mg every 3 hours as necessary.181 a

Cardiac extrasystoles: May administer 2 doses 10 minutes apart.181 a

2.5–37.5 mg.178 Usually, titrated up to 30 mg in combination with phentolamine mesylate 0.5–1 mg (range: 0.08–1.25 mg).178

Tolerance with long-term use may require dosage increase.105 114 129

Prescribing Limits

Adults

960 mg daily.

Special Populations

No special population dosage recommendations at this time.180 181

Absorption

Bioavailability

Readily absorbed from GI tract.a

Onset

Fairly rapid.a

Following intracavernosal injection, erectile response usually occurs within 10 minutes.105 106 108 112 113 114 116 118 119 129 132

Duration

Oral administration of extended-release capsules may provide continuous drug release over a 12-hour period.a

Following intracavernosal injection, erectile response may persist for 1 to several hours.105 106 108 112 113 114 116 118 119 129 132

Plasma Concentrations

Constant plasma concentrations can be maintained with oral administration at 6-hour intervals.181 a

Distribution

Extent

Distributed throughout the body, with highest concentrations in fat deposits and liver.181

Not known if papaverine distributes into human milk.181 a

Plasma Protein Binding

90%.181 a

Elimination

Metabolism

Rapidly metabolized in the liver.181 a

Elimination Route

Excreted in urine,181 a principally as inactive metabolites.181

• Advise patients receiving the drug via intracavernosal injection of potential for prolonged erections (priapism) and steps to take in the event that this serious adverse effect occurs.132 142 178 179

• Importance of seeking immediate medical attention if an erection persists >4 hours or is extremely painful.132 142

• Instruct patients receiving the drug via intracavernosal injection to visit their clinician regularly (e.g., at 3-month intervals) to assess therapeutic benefit, including the need for possible dosage adjustment, and of potential adverse effects associated with such therapy.143 147 159 167

• Importance of informing clinicians if risk factors for cardiovascular disease are present prior to initiating any treatment.a

• Importance of women informing their clinician if they are or plan to become pregnant or plan to breast-feed.180 181

• Importance of informing clinicians of existing or contemplated concomitant therapy, including prescription and OTC drugs, as well as any concomitant illnesses.180 181

• Importance of informing patients of other important precautionary information.180 181 (See Cautions.)

Excipients in commercially available drug preparations may have clinically important effects in some individuals; consult specific product labeling for details.

Please refer to the ASHP Drug Shortages Resource Center for information on shortages of one or more of these preparations.

* available from one or more manufacturer, distributor, and/or repackager by generic (nonproprietary) name