Question

Why are metabolic pathways important for urine drug testing? Discuss the reason for drug interaction and mixtures with opioids in relation to fatalities.

Answer 1

• Any xenobiotic that is ingested or administered by any other route of administration will be broken down into simpler componenets (metabolites) by the different metabolic pathways of the body. Drug tests conducted from urine samples contain these broken down simpler components. One we know how the metabolic pathways work we can predict what kind of metabolites will be formed from a certain drug. If we test for these metabolites we will be able to accurately predict what kind of drugs are int he system of the subject.
• Drug interacytions are mainly of two types - 1) Drug-Drug interaction and 2) Drug-food interaction

1. Drug-Drug interaction: The example of this will be Warfarin and Aspirin. Warfarin is an anticoagulant or a "blood-thinner" and Aspirin is a NSAID (COX-inhibitor) thats also has an anticoagulant effect. This interaction is called an additive effect and the patient is at risk of bleeding out profusely due to any injury as clotting time is significantly increased.
2. Drug-Food interaction: The example of this is Tetracycline group of antibiotics and milk. The divalent ion (Ca2+) has a chelation effect that will render the antibiotic useless.

There are many contraindications when it comes to opioids as well and these usually fall under the drug-drug interaction category. The contraindicated medications in case of opioids, leading to fatality are -

• Anti-seizure medications, such as carbamazepine , topiramate and lamotrigine
• Benzodazepines, such as diazepam , lorazepam , alprazolam and clonazepam
• Antifungals, including itraconazole , voriconazole and ketoconazole
• Antiretroviral drugs used for HIV infection, including atazanavir , indinavir and ritonavir
• Drugs for sleeping problems, such as zolpidem, eszopiclone and zaleplon
• Drugs used to treat psychiatric disorders, such as haloperidol (Haldol), clozapine, aripiprazole and quetiapine
• Medications used to treat certain types of nerve pain, such as gabapentin and pregabalin
• Muscle relaxers, such as cyclobenzaprine and baclofen

Opioid medications affect your brain and may make you sleepy. Mixing these medications with other drugs can heighten these effects, leading to slowed breathing, decreased heart rate and a risk of death.