Darvon Compound (Propoxyphene, Aspirin, and Caffeine) Drug Information: Clinical Pharmacology

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May 26, 2012

Darvon Compound

Restless Leg Syndrome »

What is restless leg syndrome (RLS)?

Restless leg syndrome (RLS, restless legs syndrome) is a common cause of painful legs. The leg pain of restless leg syndrome typically eases with motion of the legs and becomes more noticeable at rest. Restless leg syndrome also features worsening of symptoms and leg pain during the early evening or later at night.

Restless leg syndrome is often abbreviated RLS; it has also been termed shaking leg syndrome. Nighttime involuntary jerking of the legs during sleep are also known as periodic leg/limb movement disorder.

What causes restless leg syndrome?

The cause of restless leg syndrome is unknown in most people. However, restless leg syndrome has been associated with

pregnancy,
obesity,
smoking,
iron deficiency and anemia,
nerve disease,
polyneuropathy (which can be associated with hypothyroidism, heavy ...

Read the Restless Leg Syndrome article »

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Please Note: This Brand Name drug is no longer available in the US.
(Generic versions may still be available.)

CLINICAL PHARMACOLOGY

Propoxyphene is a centrally acting narcotic analgesic agent. Equimolar doses of propoxyphene hydrochloride or napsylate provide similar plasma concentrations. Following administration of 65, 130 or 195 mg of propoxyphene hydrochloride, the bioavailability of propoxyphene is equivalent to that of 100, 200, or 300 mg respectively of propoxyphene napsylate. Peak plasma concentrations of propoxyphene are reached in two to two and one-half hours. After a 65 mg oral dose of propoxyphene hydrochloride peak plasma levels of 0.05 to 0.1 mcg/ml are achieved.

Repeated doses of propoxyphene at 6-hour intervals lead to increasing plasma concentrations, with a plateau after the ninth dose at 48 hours.

Propoxyphene is metabolized in the liver to yield norpropoxyphene. Propoxyphene has a half-life of 6 to 12 hours whereas that of norpropoxyphene is 30 to 36 hours.

Norpropoxyphene has substantially less central-nevous-system-depressant effect than propoxyphene but a greater local anesthetic effect, which is similar to that of amitriptyline and antiarrhythmic agents, such as lidocaine and quinidine.

In animal studies in which propoxyphene and norpropoxyphene were continuously infused in large amounts, intracardiac conduction time (P-R and QRS intervals) was prolonged. Any intracardiac conduction delay attributable to high concentrations of norpropoxyphene may be of relatively long duration.

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Propoxyphene is a mild narcotic analgesic structurally related to methadone. The potency of propoxyphene hydrochloride is from two-thirds to equal that of codeine.

The combination of propoxyphene with a mixture of aspirin and caffeine produces greater analgesia than that produced by either propoxyphene, aspirin, and caffeine administered alone.

Last reviewed on RxList: 1/29/2005
This monograph has been modified to include the generic and brand name in many instances.