Most Common Side Effects of Opioid Use
The most common side effects of opioid use are constipation, nausea, vomiting, drowsiness, dizziness, and dry mouth, with constipation being the most persistent and requiring prophylactic management in nearly all patients. 1
Gastrointestinal Effects
Constipation is the most frequent and persistent side effect, occurring in the vast majority of patients and typically not resolving with continued use 1. Unlike other side effects where tolerance develops, constipation requires ongoing management:
- Prophylactic treatment with a stimulant laxative (such as senna) with or without a stool softener should be initiated when opioids are used for more than a few days 1
- Patients should increase hydration and fiber intake and maintain physical activity 1
- Stool softeners or fiber laxatives alone without another laxative should be avoided 1
Nausea and vomiting are also very common, particularly at initiation of therapy 1, 2, 3. These effects may require anti-emetic therapy and often improve with continued use 1.
Dry mouth is frequently reported 1.
Central Nervous System Effects
Drowsiness and sedation are among the most common CNS effects 1, 2. These typically diminish with continued use as tolerance develops 4.
Dizziness and confusion occur frequently, particularly when initiating therapy or increasing doses 1, 2.
Cognitive impairment including confusion, difficulty concentrating, and altered mental status can occur 1, 3.
Other Common Effects
Pruritus (itching) is frequently reported, occurring in ≥3% of patients 2.
Headache is common, particularly during initial therapy 2.
Insomnia and sleep disturbances occur despite the sedating properties of opioids 2.
Asthenia (weakness) is reported in ≥3% of patients 2.
Serious Adverse Effects Requiring Immediate Attention
While less common, clinicians must counsel patients about potentially life-threatening effects:
- Respiratory depression is the most serious adverse effect and can be fatal, particularly at higher doses or when combined with benzodiazepines, alcohol, or other CNS depressants 1, 2, 3
- Opioid use disorder can develop even with short-term use and represents a potentially serious lifelong condition 1
Tolerance, Dependence, and Withdrawal
Physical dependence and tolerance develop with regular use 1. Withdrawal symptoms occur when opioids are discontinued abruptly after around-the-clock use for more than a few days 1. An appropriate tapering plan should be discussed when opioids are used continuously 1.
Clinical Implications
The frequency and severity of these side effects are dose-dependent and influenced by the patient's level of opioid tolerance, clinical setting, age, renal and hepatic function, and concurrent medications 2, 4, 5. Limiting opioid use to the minimum needed to manage pain (taking only when needed rather than around-the-clock if pain is intermittent) can help limit development of tolerance and subsequent withdrawal 1.
Patients should be advised that the goal is to reduce pain to make it manageable rather than to eliminate pain completely 1, as complete pain relief is often unrealistic 1.