Controlled Drugs Flashcards
What receptors do both Methadone and Buprenorphine bind to?
- Opioid receptors
- highest affinity for miu receptors
- found in CNS, nerves in the periphery, on cells in GI tract
What is the main indication of Methadone and Buprenorphine and how do they work?
- Pain Killers/Analgesics
- work through the CNS (brain and spinal cord) to
- alter the way pain impulses arriving from peripheral nerves are processed to
- change perception and tolerance of pain
- explained by Gate Control Theory
Tell me about the Gate Control Theory of pain?
- Transmission of pain impulses can be modulated all along the spinothalmic tracts
- All along the spinal cord, interneurons can act as ‘gates’ by blocking the ascending transmission of pain impulses
- (inhibitory influence of higher brain centres on transmission of pain impulses helps explain mystery around pain- culture, learned experiences and placebo)
What is the other indication of Methadone/Buprenorphine and why?
Treatment of recreational opioid-based drug dependence
Because they act on the same opioid receptors and therefore have the same effects of;
- slow-acting pain-response inhibitors and
- decreasing respiratory activity
Whilst ALSO inhibiting the euphoria associated with recreational opioid-based drugs
What are some of the difficulties of using Methadone/Buprenorphine to treat illicit-opioid dependence?
- Extreme similarities between signs and symptoms of withdrawal from drug itself and side effects
- Reduces tolerance to drug-risk of accidental overdose
- May precipitate withdrawal (buprenorphine)
What is the mechanism of action of Methadone?
- Opioid Receptors Agonist
What is the mechanism of action of Buprenorphine?
- It both agonises and antagonises Opioid Receptors-partial agonist!
Which patients are contraindicated for Methadone use?
- Patients with respiratory depression
- Patients with acute bronchial asthma
Which patients are contraindicated for Buprenorphine use?
- Hepetitis B or C patients
- Alcohol-induced psychosis patients.
Patient Education: Possible drug interactions?
Use alongside;
- Analgesic Barbiturates
- Antipsychotics
- Benzodiazepines
- MAOIs
increases the risk of the following;
- Respiratory depression
- hypotension
- sedation
- coma
Explain the shared side effects of Methadone and Buprenorphine
Action of receptors
- in chemoreceptor trigger zone (in the brainstem)
- on GI motility (negative effects)
both lead to GI side effects of
- nausea
- vomiting
- constipation
Additionally, may lead to impotence and infertility
What are the specific side effects of Methadone?
General:
- light headedness
- sedation
- sweating
Major:
- Dependence
- Respiratory and Cardiac Arrest (call 999)
What are the specific side effects of Buprenorphine?
General;
- Dizziness
- Numbness
- Insomnia
- Headaches
Other;
- Less abuse potential as blocks opioid receptors that may be stimulated by other opioids
- Less sedating than Methadone
Tell me about the absorption rates of different administration methods for Methadone?
- IV is the most reliable way to achieve therapeutic levels
- IM and subcutaeneous offer inconsistent rates of absoprtion-heavily dependent on individual physiology
- With tablets, extra care not to cut, crush or chew as entire dose can be given at once!
- Slower in females than males
- Long-acting
Tell me about the absorption rates of different administration methods for Buprenorphine?
- IM -absorbed rapidly
- IV very rapid absorption-reaches peak levels
