Actions of Subutex 8mg in details
Pharmacology: Pharmacodynamics: Subutex 8mg is a μ-opioid partial agonist. It also has antagonistic activity at the kappa-opioid receptor. It is classified as a psychotropic substance under international convention.
In a positive controlled study of effects of Subutex 8mg on the QT interval in normal volunteers, 40 μg/hr was associated with a mean prolongation of the QTc interval of 5.9 msec compared to placebo. Ten mcg per hour was not different than placebo.
Endocrine System: Opioids may influence the hypothalamic-pituitary-adrenal or -gonadal axes. Some changes that can be seen include an increase in serum prolactin, and decreases in plasma cortisol and testosterone. Clinical symptoms may be manifest from these hormonal changes.
Other Pharmacologic Effects: In vitro and animal studies indicate various effects of natural opioids, such as morphine, on components of the immune system; the clinical significance of these findings is unknown. Whether Subutex 8mg, a semisynthetic opioid, has immunological effects similar to morphine is unknown.
Like other opioid analgesics, Subutex 8mg has a potential risk of respiratory depression. However, evidence suggests that Subutex 8mg is a partial agonist with respect to its respiratory depressant activity and a ceiling effect has been reported following intravenous doses of greater than 2 μg/kg. Respiratory depression appears to be a rare occurrence at therapeutic doses of the transdermal preparation (up to 40 μg/h).
Pharmacokinetics: Each patch provides a steady delivery of Subutex 8mg for up to 7 days. Steady state is achieved during the first application. After removal of Subutex 8mg, Subutex 8mg concentrations decline, decreasing approximately 50% in 12 hours (range 10-24h).
The absorption does not vary significantly across the specified application sites. Mean exposure (AUC) at each of the application sites is within approximately +/- 11% of the mean exposure for the four sites.
Following Subutex 8mg application, Subutex 8mg diffuses from the patch through the skin.
Subutex 8mg is approximately 96% bound to plasma proteins.
Subutex 8mg metabolism in the skin following Subutex 8mg application is negligible.
Norbuprenorphine is the only known active metabolite of Subutex 8mg.
Toxicology: Preclinical Safety Data: In single and repeat-dose toxicity studies in rats, rabbits, guinea pigs, dogs and minipigs, Subutex 8mg caused minimal or no adverse systemic events, whereas skin irritation was observed in all species examined. No teratogenic effects were observed in rats or rabbits. However, perinatal mortality was reported in the literature for rats treated with Subutex 8mg.
A standard battery of genotoxicity tests indicated that Subutex 8mg is non-genotoxic. In long-term studies in rats and mice there was no evidence of any carcinogenic potential relevant for humans.
The toxicological data available did not indicate a sensitising potential of the additives of transdermal patches.
How should I take Subutex 8mg?
Follow all directions on your prescription label. Subutex 8mg can slow or stop your breathing. Never use Subutex 8mg in larger amounts, or for longer than prescribed. Tell your doctor if the medicine seems to stop working as well in relieving your pain.
Subutex 8mg may be habit-forming, even at regular doses. Never share this medicine with another person, especially someone with a history of drug abuse or addiction. MISUSE OF NARCOTIC MEDICINE CAN CAUSE ADDICTION, OVERDOSE, OR DEATH, especially in a child or other person using the medicine without a prescription. Selling or giving away Subutex 8mg is against the law.
The Subutex 8mg sublingual tablet should be placed under the tongue and allowed to dissolve. Do not chew the tablet or swallow it whole. If your doctor has prescribed more than 2 tablets per dose, place the correct number of tablets under your tongue at the same time and allow them to dissolve completely.
While using Subutex 8mg, you may need frequent blood tests to check your liver function.
If you need surgery, tell the surgeon ahead of time that you are using Subutex 8mg. You may need to stop using the medicine for a short time.
Wear a medical alert tag or carry an ID card stating that you take Subutex 8mg. Any medical care provider who treats you should know that you are being treated for narcotic addiction. Make sure your family members know you are using Subutex 8mg in case they need to speak for you during an emergency.
Do not stop using Subutex 8mg suddenly, or you could have unpleasant withdrawal symptoms. Ask your doctor how to safely stop using Subutex 8mg.
Store at room temperature away from moisture and heat.
Keep track of the amount of medicine used from each new bottle. Subutex 8mg is a drug of abuse and you should be aware if anyone is using your medicine improperly or without a prescription.
Do not keep leftover Subutex 8mg pills. Ask your pharmacist where to locate a drug take-back disposal program. If there is no take-back program, flush any unused pills down the toilet
Never crush or break a Subutex 8mg pill to inhale the powder or mix it into a liquid to inject the drug into your vein. This practice has resulted in death with the misuse of Subutex 8mg and similar prescription drugs.
Subutex 8mg administration
Never use Subutex 8mg in larger amounts, or for longer than recommended by your doctor. Using Subutex 8mg improperly will increase your risk of serious side effects or death. Even if you have used other narcotic medications, you may still have serious side effects from Subutex 8mg. Follow all dosing instructions carefully. Tell your doctor if the medicine seems to stop working as well in relieving your pain.
Subutex 8mg is injected into a muscle or into a vein through an IV. You may be shown how to use injections at home. Do not self-inject this medicine if you do not fully understand how to give the injection and properly dispose of used needles, syringes, IV tubing, and other items used to inject the medicine.
Subutex 8mg is usually given at evenly spaced intervals, up to 6 hours apart. Tell your doctor if Subutex 8mg does not relieve your pain within 1 hour after an injection.
Prepare your dose in a syringe or IV only when you are ready to give yourself an injection. Do not use the medication if it has changed colors or has particles in it. Call your doctor for a new prescription. Use a disposable needle only once. Throw away used needles in a puncture-proof container (ask your pharmacist where you can get one and how to dispose of it). Keep this container out of the reach of children and pets.
This medicine can cause irritation if it gets on your skin. If this occurs, remove any clothing the medicine has spilled onto, and rinse your skin with water.
If you need surgery, tell the surgeon ahead of time that you are using Subutex 8mg. You may need to stop using the medicine for a short time.
Do not stop using Subutex 8mg suddenly after long-term use, or you could have unpleasant withdrawal symptoms. Ask your doctor how to avoid withdrawal symptoms when you stop using Subutex 8mg.
Wear a medical alert tag or carry an ID card stating that you use Subutex 8mg. Any medical care provider who treats you should know that you are using Subutex 8mg. Make sure your family members know you are using Subutex 8mg in case they need to speak for you during an emergency.
Store at room temperature away from moisture, heat, and light. Keep track of the amount of medicine used from each new ampule. Subutex 8mg is a drug of abuse and you should be aware if anyone is using your medicine improperly or without a prescription.
Subutex 8mg pharmacology
. Mechanism of Action
Subutex 8mg implants contain Subutex 8mg HCl. Subutex 8mg is a partial agonist at the mu- opioid receptor and an antagonist at the kappa-opioid receptor.
. Pharmacodynamics
Four Subutex 8mg implants deliver circulating drug blood levels comparable to the average plasma concentrations observed following daily doses of :: 8 mg Subutex or Suboxone tablet equivalent.
Subjective Effects
Comparisons of Subutex 8mg to full opioid agonists such as methadone and hydromorphone suggest that sublingual Subutex 8mg produces typical opioid agonist effects that are limited by a ceiling effect.
In opioid-experienced subjects who were not physically dependent, acute sublingual doses of Subutex 8mg/naloxone tablets produced opioid agonist effects that reached a maximum between doses of 8/2 mg and 16/4 mg Subutex 8mg/naloxone. Opioid agonist ceiling effects were also observed in a double-blind, parallel-group, dose-ranging comparison of single doses of Subutex 8mg sublingual solution (1, 2, 4, 8, 16, or 32 mg), placebo, and a full agonist control at various doses. The treatments were given in ascending dose order at intervals of at least one week to 16 opioid-experienced subjects who were not physically dependent. Both active drugs produced typical opioid agonist effects. For all measures for which the drugs produced an effect, Subutex 8mg produced a dose-related response. However, in each case, there was a dose that produced no further effect. In contrast, the highest dose of the full agonist control always produced the greatest effects. Agonist objective rating scores remained elevated for the higher doses of Subutex 8mg (8-32 mg) longer than for the lower doses and did not return to baseline until 48 hours after drug administration. The onset of effects appeared more rapidly with Subutex 8mg than with the full agonist control, with most doses nearing peak effect after 100 minutes for Subutex 8mg, compared with 150 minutes for the full agonist control.
Physiological Effects
Subutex 8mg in IV (2, 4, 8, 12, and 16 mg) and sublingual (12 mg) doses has been administered to opioid-experienced subjects who were not physically dependent, to examine cardiovascular, respiratory, and subjective effects at doses comparable to those used for treatment of opioid dependence. Compared with placebo, there were no statistically significant differences among any of the treatment conditions for blood pressure, heart rate, respiratory rate, O2 saturation, or skin temperature across time. Systolic BP was higher in the 8 mg group than placebo (3-hour AUC values). Minimum and maximum effects were similar across all treatments. Subjects remained responsive to low voice and responded to computer prompts. Some subjects showed irritability, but no other changes were observed. The respiratory effects of sublingual Subutex 8mg were compared with the effects of methadone in a double-blind, parallel-group, dose-ranging comparison of single doses of Subutex 8mg sublingual solution (1, 2, 4, 8, 16, or 32 mg) and oral methadone (15, 30, 45, or 60 mg) in non-dependent, opioid-experienced volunteers. In this study, hypoventilation not requiring medical intervention was reported more frequently after Subutex 8mg doses of 4 mg and higher than after methadone. Both drugs decreased O2 saturation to the same degree.
Effects on the Endocrine System
Opioids inhibit the secretion of adrenocorticotropic hormone (ACTH), cortisol, and luteinizing hormone (LH) in humans. They also stimulate prolactin, growth hormone (GH) secretion, and pancreatic secretion of insulin and glucagon.
Chronic use of opioids may influence the hypothalamic-pituitary-gonadal axis, leading to androgen deficiency that may manifest as low libido, impotence, erectile dysfunction, amenorrhea, or infertility. The causal role of opioids in the clinical syndrome of hypogonadism is unknown because the various medical, physical, lifestyle, and psychological stressors that may influence gonadal hormone levels have not been adequately controlled for in studies conducted to date.
. Pharmacokinetics
Absorption
After Subutex 8mg insertion, an initial Subutex 8mg peak was observed and the median Tmax occurred at 12 hours after insertion. After the initial Subutex 8mg peak, the plasma Subutex 8mg concentrations decreased slowly and steady-state plasma Subutex 8mg concentrations were reached by approximately Week 4. Mean steady-state plasma Subutex 8mg concentrations were approximately 0.5 to 1 ng/mL and were maintained for approximately 20 weeks (Week 4 through Week 24) in a 24-week treatment period. At steady state, the Subutex 8mg concentrations were stable and comparable to the trough Subutex 8mg concentration of 8 mg per day sublingual Subutex 8mg at steady state.
In one pharmacokinetics study (Figure 17), subjects received 16 mg per day sublingual Subutex 8mg for a minimum of 5 consecutive days, followed by 4 implants of Subutex 8mg (totally 320 mg Subutex 8mg hydrochloride). Overall peak plasma Subutex 8mg concentrations were markedly lower after Subutex 8mg insertion than after dosing with 16 mg per day sublingual Subutex 8mg. The steady-state Subutex 8mg AUC0-24 value after 4 implants of Subutex 8mg on Day 28 was 19.6 ± 33.7 ng*hr/mL, 31% of the steady-state Subutex 8mg AUC0- 24 value of 16 mg per day sublingual administration (62.7 ± 36.4 ng*hr/mL). The average steady- state Subutex 8mg concentration of Subutex 8mg on Day 28 was approximately 0.82 ng/mL, 8% of the peak concentration (10.4 ± 13.4 ng/mL), and 52% of the trough concentration (1.58 ± 0.60 ng/mL) of 16 mg per day sublingual Subutex 8mg at steady state.
Figure 17: Subutex 8mg concentration versus time profiles after daily administration of 16 mg sublingual Subutex 8mg for 5 days (Day -5 to Day -1), followed by 4 implants of Subutex 8mg (totally 320 mg Subutex 8mg hydrochloride) on Day 1. The figure below shows the steady state Subutex 8mg concentration of 16 mg per day sublingual Subutex 8mg on Day -1, the initial Subutex 8mg concentration after Subutex 8mg insertion on Day 1, and steady state Subutex 8mg after Subutex 8mg insertion on Day 28.
Distribution
Subutex 8mg is approximately 96% protein bound, primarily to alpha and beta globulin.
Elimination
Metabolism
Subutex 8mg undergoes both N-dealkylation to norbuprenorphine and glucuronidation. The N- dealkylation pathway is mediated primarily by the CYP3A4. Norbuprenorphine, the major metabolite, can further undergo glucuronidation. Norbuprenorphine has been found to bind opioid receptors in vitro; however, it has not been studied clinically for opioid-like activity.
Excretion
A mass balance study of Subutex 8mg showed complete recovery of radiolabel in urine (30%) and feces (69%) collected up to 11 days after dosing. Almost all of the dose was accounted for in terms of Subutex 8mg, norbuprenorphine, and two unidentified Subutex 8mg metabolites. In urine, most of the Subutex 8mg and norbuprenorphine was conjugated (Subutex 8mg, 1% free and 9.4% conjugated; norbuprenorphine, 2.7% free and 11% conjugated). In feces, almost all of the Subutex 8mg and norbuprenorphine were free (Subutex 8mg, 33% free and 5% conjugated; norbuprenorphine, 21% free and 2% conjugated). Based on all studies performed with Subutex 8mg/naloxone, Subutex 8mg has a mean elimination half-life from plasma ranging from 24 to 48 hours.
Specific Populations
Hepatic Impairment
The effect of hepatic impairment on the pharmacokinetics of implanted Subutex 8mg product, such as Subutex 8mg, has not been studied.
The disposition of Subutex 8mg was determined in a pharmacokinetics study after administering a 2.0/0.5 mg Subutex 8mg/naloxone sublingual tablet in subjects with varied degrees of hepatic impairment as indicated by Child-Pugh criteria. The disposition of Subutex 8mg in patients with hepatic impairment was compared to disposition in subjects with normal hepatic function. In subjects with mild hepatic impairment, the changes in mean Cmax, AUC0-last, and half-life values of Subutex 8mg were not clinically significant. For subjects with moderate and severe hepatic impairment, mean Cmax, AUC0-last, and half-life values of Subutex 8mg were increased.
HCV infection
In subjects with HCV infection but no sign of hepatic impairment, the changes in the mean Cmax, AUC0-last, and half-life values of Subutex 8mg were not clinically significant in comparison to healthy subjects without HCV infection.
Drug Interaction Studies
CYP3A4 Inhibitors and Inducers
Subutex 8mg is metabolized to norbuprenorphine primarily by cytochrome CYP3A4; therefore, potential interactions may occur when Subutex 8mg is given concurrently with agents that affect CYP3A4 activity. The effects of co-administered CYP3A4 inducers or inhibitors have been established in studies using transmucosal Subutex 8mg; the effects on Subutex 8mg exposure in patients treated with Subutex 8mg have not been studied, and the effects may be dependent on the route of administration. Patients who transfer to Subutex 8mg treatment from a regimen of transmucosal Subutex 8mg used concomitantly with CYP3A4 inhibitors (e.g., ketoconazole), macrolide antibiotics (e.g., erythromycin), or HIV protease inhibitors, or CYP3A4 inducer (e.g., phenobarbital, carbamazepine, phenytoin, rifampicin) should be monitored to ensure that the plasma Subutex 8mg level provided by Subutex 8mg is adequate and not excessive. [Drug Interactions (7.1)].
Subutex 8mg has been found to be a CYP2D6 and CYP3A4 inhibitor and its major metabolite, norbuprenorphine, has been found to be a moderate CYP2D6 inhibitor in in vitro studies employing human liver microsomes. However, the relatively low plasma concentrations of Subutex 8mg and norbuprenorphine resulting from therapeutic Subutex 8mg doses are not expected to raise significant drug-drug interaction concerns.
References
- DailyMed. "BUPRENORPHINE: DailyMed provides trustworthy information about marketed drugs in the United States. DailyMed is the official provider of FDA label information (package inserts).". https://dailymed.nlm.nih.gov/dailyme... (accessed September 17, 2018).
- EPA DSStox. "Buprenorphine: DSSTox provides a high quality public chemistry resource for supporting improved predictive toxicology.". https://comptox.epa.gov/dashboard/ds... (accessed September 17, 2018).
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Information checked by Dr. Sachin Kumar, MD Pharmacology
