During clinical trials, the most frequently reported adverse reactions were dizziness, sedation, nausea, and vomiting. Other adverse reactions include constipation, abdominal pain, skin rashes, lightheadedness, headache, weakness, euphoria, dysphoria, hallucinations, and minor visual disturbances.
The most frequently reported postmarketing adverse events have included completed suicide, accidental and intentional overdose, drug dependence, cardiac arrest, coma, drug ineffective, drug toxicity, nausea, respiratory arrest, cardio-respiratory arrest, death, vomiting, dizziness, convulsion, confusional state, and diarrhea.
Additional adverse experiences reported through postmarketing surveillance include:
Cardiac disorders: arrhythmia, bradycardia, cardiac/respiratory arrest, congestive arrest, congestive heart failure (CHF), tachycardia, myocardial infarction (MI)
Eye disorder: eye swelling, vision blurred
General disorder and administration site conditions: drug ineffective, drug interaction, drug tolerance, influenza type illness, drug withdrawal syndrome
Gastrointestinal disorder: gastrointestinal bleed, acute pancreatitis
Hepatobiliary disorder: hepatic steatosis, hepatomegaly, hepatocellular injury
Immune system disorder: hypersensitivity
Injury poisoning and procedural complications: drug toxicity, hip fracture, multiple drug overdose, narcotic overdose
Investigations: blood pressure decreased, heart rate elevated/abnormal
Metabolism and nutrition disorder: metabolic acidosis
Nervous system disorder: ataxia, coma, dizziness, somnolence, syncope
Psychiatric: abnormal behavior, confusional state, hallucinations, mental status change
Respiratory, thoracic, and mediastinal disorders: respiratory depression, dyspnoea
Skin and subcutaneous tissue disorder: rash, itch
Liver dysfunction has been reported in association with both active components of Darvocet-N (propoxyphene napsylate and acetaminophen) 50 and Darvocet-N (propoxyphene napsylate and acetaminophen) 100. Propoxyphene therapy has been associated with abnormal liver function tests and, more rarely, with instances of reversible jaundice (including cholestatic jaundice). Hepatic necrosis may result from acute overdose of acetaminophen (see OVERDOSAGE). In chronic ethanol abusers, this has been reported rarely with short-term use of acetaminophen dosages of 2.5 to 10 g/day. Fatalities have occurred.
There have also been postmarketing reports of renal papillary necrosis associated with chronic acetaminophen use, particularly when the dosage is greater than recommended and when combined with aspirin. Subacute painful myopathy has been reported following chronic propoxyphene overdosage.
Drug Abuse And Dependence
Darvocet-N (propoxyphene napsylate and acetaminophen) is a Schedule IV narcotic under the U.S. Controlled Substances Act. Darvocet-N (propoxyphene napsylate and acetaminophen) can produce drug dependence of the morphine type, and therefore, has the potential for being abused. Psychic dependence, physical dependence and tolerance may develop upon repeated administration. Darvocet-N (propoxyphene napsylate and acetaminophen) should be prescribed and administered with the same degree of caution appropriate to the use of other narcotic-containing medications.
Since Darvocet-N (propoxyphene napsylate and acetaminophen) is a mu-opioid agonist, it may be subject to misuse, abuse, and addiction. Addiction to opioids prescribed for pain management has not been estimated. However, requests for opioids from opioid-addicted patients occur. As such, physicians should take appropriate care in prescribing Darvocet-N (propoxyphene napsylate and acetaminophen) .
Opioid analgesics may cause psychological and physical dependence. Physical dependence results in withdrawal symptoms in patients who abruptly discontinue the drug after long term administration. Also, symptoms of withdrawal may be precipitated through the administration of drugs with mu-opioid antagonist activity, e.g., naloxone or mixed agonist/antagonist analgesics (pentazocine, butorphanol, nalbuphine, dezocine) (see OVERDOSAGE). Physical dependence usually does not occur to a clinically significant degree, until after several weeks of continued opioid usage. Tolerance, in which increasingly larger doses are required to produce the same degree of analgesia, is initially manifested by a shortened duration of an analgesic effect and subsequently, by decreases in the intensity of analgesia.
In chronic pain patients, and in opioid-tolerant cancer patients, the administration of Darvocet-N (propoxyphene napsylate and acetaminophen) should be guided by the degree of tolerance manifested and the doses needed to adequately relieve pain.
The severity of the Darvocet-N (propoxyphene napsylate and acetaminophen) abstinence syndrome may depend on the degree of physical dependence. Withdrawal is characterized by rhinitis, myalgia, abdominal cramping, and occasional diarrhea. Most observable symptoms disappear in 5 to 14 days without treatment; however, there may be a phase of secondary or chronic abstinence which may last for 2 to 6 months characterized by insomnia, irritability, and muscular aches. The patient may be detoxified by gradual reduction of the dose. Gastrointestinal disturbances or dehydration should be treated with supportive care.