physics

Physical dependence

Physical dependence is a physics topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Physical dependence rather than just read about it. In short: Physical dependence is a physical condition caused by chronic use of a tolerance-forming drug, in which abrupt or gradual drug withdrawal causes unpleasant physical symptoms. Physical dependence can develop from low-dose therapeutic use of certain medications such as benzodiazepines, opioids, stimulants, antiepileptics and antidepressants, as well as the recreational misuse of drugs such as alcohol, opioids and benz…

Key takeaways

Physical dependence belongs to physics; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Physical dependence to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Physical dependence from memory before moving on to harder problems.

Reference excerpt

Physical dependence is a physical condition caused by chronic use of a tolerance-forming drug, in which abrupt or gradual drug withdrawal causes unpleasant physical symptoms. Physical dependence can develop from low-dose therapeutic use of certain medications such as benzodiazepines, opioids, stimulants, antiepileptics and antidepressants, as well as the recreational misuse of drugs such as alcohol, opioids and benzodiazepines. The higher the dose used, the greater the duration of use, and the earlier age use began are predictive of worsened physical dependence and thus more severe withdrawal syndromes. Acute withdrawal syndromes can last days, weeks or months. Protracted withdrawal syndrome, also known as post-acute-withdrawal syndrome or "PAWS", is a low-grade continuation of some of the symptoms of acute withdrawal, typically in a remitting-relapsing pattern, often resulting in relapse and prolonged disability of a degree to preclude the possibility of lawful employment. Protracted withdrawal syndrome can last for months, years, or depending on individual factors, indefinitely. Protracted withdrawal syndrome is noted to be most often caused by benzodiazepines as well as opioids. To dispel the popular misassociation with addiction, physical dependence to medications is sometimes compared to dependence on insulin by persons with diabetes.

Symptoms Physical dependence can manifest itself in the appearance of both physical and psychological symptoms which are caused by physiological adaptions in the central nervous system and the brain due to chronic exposure to a substance. Symptoms which may be experienced during withdrawal or reduction in dosage include increased heart rate and/or blood pressure, sweating, and tremors. More serious withdrawal symptoms such as confusion, seizures, and visual hallucinations indicate a serious emergency and the need for immediate medical care. Sedative hypnotic drugs such as alcohol, benzodiazepines, and barbiturates are the only commonly available substances that can be fatal in withdrawal due to their propensity to induce withdrawal convulsions. Abrupt withdrawal from other drugs, such as opioids can cause an extremely painful withdrawal that is very rarely fatal in patients of general good health and with medical treatment, but is more often fatal in patients with weakened cardiovascular systems; toxicity is generally caused by the often-extreme increases in heart rate and blood pressure (which can be treated with clonidine), or due to arrhythmia due to electrolyte imbalance caused by the inability to eat, and constant diarrhea and vomiting (which can be treated with loperamide and ondansetron respectively) associated with acute opioid withdrawal, especially in longer-acting substances where the diarrhea and emesis can continue unabated for weeks, although life-threatening complications are extremely rare, and nearly non-existent with proper medical management.

Treatment Treatment for physical dependence depends upon the drug being withdrawn and often includes administration of another drug, especially for substances that can be dangerous when abruptly discontinued or when previous attempts have failed. Physical dependence is usually managed by a slow dose reduction over a period of weeks, months or sometimes longer depending on the drug, dose and the individual. A physical dependence on alcohol is often managed with a cross tolerant drug, such as long acting benzodiazepines to manage the alcohol withdrawal symptoms.

Drugs that cause physical dependence All μ-opioids with any (even slight) agonist effect, such as (partial list) morphine, heroin, codeine, oxycodone, buprenorphine, nalbuphine, methadone, and fentanyl, but not agonists specific to non-μ opioid receptors, such as salvinorin A (a k-opioid agonist), nor opioid antagonists or inverse agonists, such as naltrexone (a universal opioid inverse agonist) All GABA agonists and positive allosteric modulators of both the GABA-A ionotropic receptor and GABA-B metabotropic receptor subunits, including (partial list): alcohol (alcoholic beverage) (cf. alcohol dependence, alcohol withdrawal, delirium tremens) barbiturates such as phenobarbital, sodium thiopental and secobarbital benzodiazepines such as diazepam (Valium), lorazepam (Ativan), and alprazolam (Xanax) (see benzodiazepine dependence and benzodiazepine withdrawal syndrome) nonbenzodiazepine hypnotics (z-drugs) such as zopiclone and zolpidem. gamma-hydroxybutyric acid (GHB) and 1,4-butanediol carisoprodol (Soma) and related carbamates (tybamate, meprobamate, ethinamate etc.) baclofen (Lioresal) and its non-chlorinated analogue phenibut chloral hydrate glutethimide clomethiazole methaqualone (Quaalude) Nicotine (tobacco) (cf. nicotine withdrawal) Gabapentinoids such as gabapentin (Neurontin), Pregabalin (Lyrica), and phenibut (Noofen), Baclofen (Lioresal), which are inhibitors of α2δ subunit-containing VDCCsTooltip voltage-dependent calcium channels Antiepileptic drugs such as valproate, lamotrigine, tiagabine, vigabatrin, carbamazepine and oxcarbazepine, and topiramate Antipsychotic drugs such as clozapine, risperidone, olanzapine, haloperidol, thioridazine, etc. Commonly prescribed antidepressants such as the selective serotonin reuptake inhibitors (SSRIs) and serotonin-norepinephrine reuptake inhibitors (SNRIs) (cf. SSRI/SNRI withdrawal syndrome) Sympatholytic medications, including beta blockers such as propranolol and alpha-adrenergic agonists such as clonidine Androgenic-anabolic steroids Glucocorticoids Other topical decongestants such as xylometazoline and oxymetazoline

Rebound syndrome

… excerpt ends here. Continue reading the full article.

Worked examples

Example 1 — a first encounter with Physical dependence

Start with the simplest possible case. Write down what Physical dependence claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In physics, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Physical dependence before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Physical dependence ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Physical dependence

In research: Physical dependence appears in physics research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Physical dependence in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Physical dependence is common in secondary-school and first-year university syllabi. It links to neighbouring topics Causes of death, Substance-related disorders, Substance dependence, so understanding it makes those chapters shorter.
In everyday life: Look for Physical dependence outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Physical dependence in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Physical dependence means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Physical dependence out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Physical dependence in simple terms?

Why does Physical dependence matter?

Because it connects several physics ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Physical dependence?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Physical dependence.